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docs: hid: convert to ReST 

Rename the HID documentation files to ReST, add an
index for them and adjust in order to produce a nice html
output via the Sphinx build system.

While here, fix the sysfs example from hid-sensor.txt, that
has a lot of "?" instead of the proper UTF-8 characters that
are produced by the tree command.

At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Acked-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
This commit is contained in:
Mauro Carvalho Chehab 2019-06-28 09:19:59 -03:00 коммит произвёл Benjamin Tissoires
Родитель 763cf1f2d9
Коммит cca4786174
11 изменённых файлов: 897 добавлений и 676 удалений
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85
Documentation/hid/hid-alps.txt → Documentation/hid/hid-alps.rst
Просмотреть файл

@ -1,19 +1,26 @@
==========================
ALPS HID Touchpad Protocol
----------------------
==========================
Introduction
------------
Currently ALPS HID driver supports U1 Touchpad device.
U1 devuce basic information.
U1 device basic information.
========== ======
Vender ID 0x044E
Product ID 0x120B
Version ID 0x0121
========== ======
HID Descriptor
------------
--------------
======= ==================== ===== =======================================
Byte Field Value Notes
======= ==================== ===== =======================================
0 wHIDDescLength 001E Length of HID Descriptor : 30 bytes
2 bcdVersion 0100 Compliant with Version 1.00
4 wReportDescLength 00B2 Report Descriptor is 178 Bytes (0x00B2)
@ -28,32 +35,42 @@ Byte Field Value Notes
22 wProductID 120B Product ID 0x120B
24 wVersionID 0121 Version 01.21
26 RESERVED 0000 RESERVED
======= ==================== ===== =======================================
Report ID
------------
ReportID-1 (Input Reports) (HIDUsage-Mouse) for TP&SP
ReportID-2 (Input Reports) (HIDUsage-keyboard) for TP
ReportID-3 (Input Reports) (Vendor Usage: Max 10 finger data) for TP
ReportID-4 (Input Reports) (Vendor Usage: ON bit data) for GP
ReportID-5 (Feature Reports) Feature Reports
ReportID-6 (Input Reports) (Vendor Usage: StickPointer data) for SP
ReportID-7 (Feature Reports) Flash update (Bootloader)
---------
========== ================= =========================================
ReportID-1 (Input Reports) (HIDUsage-Mouse) for TP&SP
ReportID-2 (Input Reports) (HIDUsage-keyboard) for TP
ReportID-3 (Input Reports) (Vendor Usage: Max 10 finger data) for TP
ReportID-4 (Input Reports) (Vendor Usage: ON bit data) for GP
ReportID-5 (Feature Reports) Feature Reports
ReportID-6 (Input Reports) (Vendor Usage: StickPointer data) for SP
ReportID-7 (Feature Reports) Flash update (Bootloader)
========== ================= =========================================
Data pattern
------------
===== ========== ===== =================
Case1 ReportID_1 TP/SP Relative/Relative
Case2 ReportID_3 TP Absolute
ReportID_6 SP Absolute
===== ========== ===== =================
Command Read/Write
------------------
To read/write to RAM, need to send a commands to the device.
The command format is as below.
DataByte(SET_REPORT)
===== ======================
Byte1 Command Byte
Byte2 Address - Byte 0 (LSB)
Byte3 Address - Byte 1
@ -61,13 +78,19 @@ Byte4 Address - Byte 2
Byte5 Address - Byte 3 (MSB)
Byte6 Value Byte
Byte7 Checksum
===== ======================
Command Byte is read=0xD1/write=0xD2 .
Address is read/write RAM address.
Value Byte is writing data when you send the write commands.
When you read RAM, there is no meaning.
DataByte(GET_REPORT)
===== ======================
Byte1 Response Byte
Byte2 Address - Byte 0 (LSB)
Byte3 Address - Byte 1
@ -75,6 +98,7 @@ Byte4 Address - Byte 2
Byte5 Address - Byte 3 (MSB)
Byte6 Value Byte
Byte7 Checksum
===== ======================
Read value is stored in Value Byte.
@ -82,7 +106,11 @@ Read value is stored in Value Byte.
Packet Format
Touchpad data byte
------------------
b7 b6 b5 b4 b3 b2 b1 b0
======= ======= ======= ======= ======= ======= ======= ======= =====
- b7 b6 b5 b4 b3 b2 b1 b0
======= ======= ======= ======= ======= ======= ======= ======= =====
1 0 0 SW6 SW5 SW4 SW3 SW2 SW1
2 0 0 0 Fcv Fn3 Fn2 Fn1 Fn0
3 Xa0_7 Xa0_6 Xa0_5 Xa0_4 Xa0_3 Xa0_2 Xa0_1 Xa0_0
@ -114,17 +142,25 @@ Touchpad data byte
25 Ya4_7 Ya4_6 Ya4_5 Ya4_4 Ya4_3 Ya4_2 Ya4_1 Ya4_0
26 Ya4_15 Ya4_14 Ya4_13 Ya4_12 Ya4_11 Ya4_10 Ya4_9 Ya4_8
27 LFB4 Zs4_6 Zs4_5 Zs4_4 Zs4_3 Zs4_2 Zs4_1 Zs4_0
======= ======= ======= ======= ======= ======= ======= ======= =====
SW1-SW6: SW ON/OFF status
Xan_15-0(16bit):X Absolute data of the "n"th finger
Yan_15-0(16bit):Y Absolute data of the "n"th finger
Zsn_6-0(7bit): Operation area of the "n"th finger
SW1-SW6:
SW ON/OFF status
Xan_15-0(16bit):
X Absolute data of the "n"th finger
Yan_15-0(16bit):
Y Absolute data of the "n"th finger
Zsn_6-0(7bit):
Operation area of the "n"th finger
StickPointer data byte
------------------
b7 b6 b5 b4 b3 b2 b1 b0
----------------------
======= ======= ======= ======= ======= ======= ======= ======= =====
- b7 b6 b5 b4 b3 b2 b1 b0
======= ======= ======= ======= ======= ======= ======= ======= =====
Byte1 1 1 1 0 1 SW3 SW2 SW1
Byte2 X7 X6 X5 X4 X3 X2 X1 X0
Byte3 X15 X14 X13 X12 X11 X10 X9 X8
@ -132,8 +168,13 @@ Byte4 Y7 Y6 Y5 Y4 Y3 Y2 Y1 Y0
Byte5 Y15 Y14 Y13 Y12 Y11 Y10 Y9 Y8
Byte6 Z7 Z6 Z5 Z4 Z3 Z2 Z1 Z0
Byte7 T&P Z14 Z13 Z12 Z11 Z10 Z9 Z8
======= ======= ======= ======= ======= ======= ======= ======= =====
SW1-SW3: SW ON/OFF status
Xn_15-0(16bit):X Absolute data
Yn_15-0(16bit):Y Absolute data
Zn_14-0(15bit):Z
SW1-SW3:
SW ON/OFF status
Xn_15-0(16bit):
X Absolute data
Yn_15-0(16bit):
Y Absolute data
Zn_14-0(15bit):
Z

192
Documentation/hid/hid-sensor.txt → Documentation/hid/hid-sensor.rst
Просмотреть файл

@ -1,6 +1,6 @@
=====================
HID Sensors Framework
======================
=====================
HID sensor framework provides necessary interfaces to implement sensor drivers,
which are connected to a sensor hub. The sensor hub is a HID device and it provides
a report descriptor conforming to HID 1.12 sensor usage tables.
@ -15,22 +15,22 @@ the drivers themselves."
This specification describes many usage IDs, which describe the type of sensor
and also the individual data fields. Each sensor can have variable number of
data fields. The length and order is specified in the report descriptor. For
example a part of report descriptor can look like:
example a part of report descriptor can look like::
INPUT(1)[INPUT]
..
Field(2)
Physical(0020.0073)
Usage(1)
0020.045f
Logical Minimum(-32767)
Logical Maximum(32767)
Report Size(8)
Report Count(1)
Report Offset(16)
Flags(Variable Absolute)
..
..
INPUT(1)[INPUT]
..
Field(2)
Physical(0020.0073)
Usage(1)
0020.045f
Logical Minimum(-32767)
Logical Maximum(32767)
Report Size(8)
Report Count(1)
Report Offset(16)
Flags(Variable Absolute)
..
..
The report is indicating "sensor page (0x20)" contains an accelerometer-3D (0x73).
This accelerometer-3D has some fields. Here for example field 2 is motion intensity
@ -40,13 +40,14 @@ data will use this format.
Implementation
=================
==============
This specification defines many different types of sensors with different sets of
data fields. It is difficult to have a common input event to user space applications,
for different sensors. For example an accelerometer can send X,Y and Z data, whereas
an ambient light sensor can send illumination data.
So the implementation has two parts:
- Core hid driver
- Individual sensor processing part (sensor drivers)
@ -55,8 +56,11 @@ Core driver
The core driver registers (hid-sensor-hub) registers as a HID driver. It parses
report descriptors and identifies all the sensors present. It adds an MFD device
with name HID-SENSOR-xxxx (where xxxx is usage id from the specification).
For example
For example:
HID-SENSOR-200073 is registered for an Accelerometer 3D driver.
So if any driver with this name is inserted, then the probe routine for that
function will be called. So an accelerometer processing driver can register
with this name and will be probed if there is an accelerometer-3D detected.
@ -66,7 +70,8 @@ drivers to register and get events for that usage id. Also it provides parsing
functions, which get and set each input/feature/output report.
Individual sensor processing part (sensor drivers)
-----------
--------------------------------------------------
The processing driver will use an interface provided by the core driver to parse
the report and get the indexes of the fields and also can get events. This driver
can use IIO interface to use the standard ABI defined for a type of sensor.
@ -75,31 +80,34 @@ can use IIO interface to use the standard ABI defined for a type of sensor.
Core driver Interface
=====================
Callback structure:
Each processing driver can use this structure to set some callbacks.
Callback structure::
Each processing driver can use this structure to set some callbacks.
int (*suspend)(..): Callback when HID suspend is received
int (*resume)(..): Callback when HID resume is received
int (*capture_sample)(..): Capture a sample for one of its data fields
int (*send_event)(..): One complete event is received which can have
multiple data fields.
Registration functions:
int sensor_hub_register_callback(struct hid_sensor_hub_device *hsdev,
Registration functions::
int sensor_hub_register_callback(struct hid_sensor_hub_device *hsdev,
u32 usage_id,
struct hid_sensor_hub_callbacks *usage_callback):
Registers callbacks for an usage id. The callback functions are not allowed
to sleep.
to sleep::
int sensor_hub_remove_callback(struct hid_sensor_hub_device *hsdev,
int sensor_hub_remove_callback(struct hid_sensor_hub_device *hsdev,
u32 usage_id):
Removes callbacks for an usage id.
Parsing function:
int sensor_hub_input_get_attribute_info(struct hid_sensor_hub_device *hsdev,
Parsing function::
int sensor_hub_input_get_attribute_info(struct hid_sensor_hub_device *hsdev,
u8 type,
u32 usage_id, u32 attr_usage_id,
struct hid_sensor_hub_attribute_info *info);
@ -110,26 +118,27 @@ so that fields can be set or get individually.
These indexes avoid searching every time and getting field index to get or set.
Set Feature report
int sensor_hub_set_feature(struct hid_sensor_hub_device *hsdev, u32 report_id,
Set Feature report::
int sensor_hub_set_feature(struct hid_sensor_hub_device *hsdev, u32 report_id,
u32 field_index, s32 value);
This interface is used to set a value for a field in feature report. For example
if there is a field report_interval, which is parsed by a call to
sensor_hub_input_get_attribute_info before, then it can directly set that individual
field.
sensor_hub_input_get_attribute_info before, then it can directly set that
individual field::
int sensor_hub_get_feature(struct hid_sensor_hub_device *hsdev, u32 report_id,
int sensor_hub_get_feature(struct hid_sensor_hub_device *hsdev, u32 report_id,
u32 field_index, s32 *value);
This interface is used to get a value for a field in input report. For example
if there is a field report_interval, which is parsed by a call to
sensor_hub_input_get_attribute_info before, then it can directly get that individual
field value.
sensor_hub_input_get_attribute_info before, then it can directly get that
individual field value::
int sensor_hub_input_attr_get_raw_value(struct hid_sensor_hub_device *hsdev,
int sensor_hub_input_attr_get_raw_value(struct hid_sensor_hub_device *hsdev,
u32 usage_id,
u32 attr_usage_id, u32 report_id);
@ -143,6 +152,8 @@ registered callback function to process the sample.
----------
HID Custom and generic Sensors
------------------------------
HID Sensor specification defines two special sensor usage types. Since they
don't represent a standard sensor, it is not possible to define using Linux IIO
@ -158,66 +169,73 @@ keyboard attached/detached or lid open/close.
To allow application to utilize these sensors, here they are exported uses sysfs
attribute groups, attributes and misc device interface.
An example of this representation on sysfs:
/sys/devices/pci0000:00/INT33C2:00/i2c-0/i2c-INT33D1:00/0018:8086:09FA.0001/HID-SENSOR-2000e1.6.auto$ tree -R
.
????????? enable_sensor
????????? feature-0-200316
??????? ????????? feature-0-200316-maximum
??????? ????????? feature-0-200316-minimum
??????? ????????? feature-0-200316-name
??????? ????????? feature-0-200316-size
??????? ????????? feature-0-200316-unit-expo
??????? ????????? feature-0-200316-units
??????? ????????? feature-0-200316-value
????????? feature-1-200201
??????? ????????? feature-1-200201-maximum
??????? ????????? feature-1-200201-minimum
??????? ????????? feature-1-200201-name
??????? ????????? feature-1-200201-size
??????? ????????? feature-1-200201-unit-expo
??????? ????????? feature-1-200201-units
??????? ????????? feature-1-200201-value
????????? input-0-200201
??????? ????????? input-0-200201-maximum
??????? ????????? input-0-200201-minimum
??????? ????????? input-0-200201-name
??????? ????????? input-0-200201-size
??????? ????????? input-0-200201-unit-expo
??????? ????????? input-0-200201-units
??????? ????????? input-0-200201-value
????????? input-1-200202
??????? ????????? input-1-200202-maximum
??????? ????????? input-1-200202-minimum
??????? ????????? input-1-200202-name
??????? ????????? input-1-200202-size
??????? ????????? input-1-200202-unit-expo
??????? ????????? input-1-200202-units
??????? ????????? input-1-200202-value
An example of this representation on sysfs::
/sys/devices/pci0000:00/INT33C2:00/i2c-0/i2c-INT33D1:00/0018:8086:09FA.0001/HID-SENSOR-2000e1.6.auto$ tree -R
.
│   ├── enable_sensor
│   │   ├── feature-0-200316
│   │   │   ├── feature-0-200316-maximum
│   │   │   ├── feature-0-200316-minimum
│   │   │   ├── feature-0-200316-name
│   │   │   ├── feature-0-200316-size
│   │   │   ├── feature-0-200316-unit-expo
│   │   │   ├── feature-0-200316-units
│   │   │   ├── feature-0-200316-value
│   │   ├── feature-1-200201
│   │   │   ├── feature-1-200201-maximum
│   │   │   ├── feature-1-200201-minimum
│   │   │   ├── feature-1-200201-name
│   │   │   ├── feature-1-200201-size
│   │   │   ├── feature-1-200201-unit-expo
│   │   │   ├── feature-1-200201-units
│   │   │   ├── feature-1-200201-value
│   │   ├── input-0-200201
│   │   │   ├── input-0-200201-maximum
│   │   │   ├── input-0-200201-minimum
│   │   │   ├── input-0-200201-name
│   │   │   ├── input-0-200201-size
│   │   │   ├── input-0-200201-unit-expo
│   │   │   ├── input-0-200201-units
│   │   │   ├── input-0-200201-value
│   │   ├── input-1-200202
│   │   │   ├── input-1-200202-maximum
│   │   │   ├── input-1-200202-minimum
│   │   │   ├── input-1-200202-name
│   │   │   ├── input-1-200202-size
│   │   │   ├── input-1-200202-unit-expo
│   │   │   ├── input-1-200202-units
│   │   │   ├── input-1-200202-value
Here there is a custom sensors with four fields, two feature and two inputs.
Each field is represented by a set of attributes. All fields except the "value"
are read only. The value field is a RW field.
Example
/sys/bus/platform/devices/HID-SENSOR-2000e1.6.auto/feature-0-200316$ grep -r . *
feature-0-200316-maximum:6
feature-0-200316-minimum:0
feature-0-200316-name:property-reporting-state
feature-0-200316-size:1
feature-0-200316-unit-expo:0
feature-0-200316-units:25
feature-0-200316-value:1
Example::
/sys/bus/platform/devices/HID-SENSOR-2000e1.6.auto/feature-0-200316$ grep -r . *
feature-0-200316-maximum:6
feature-0-200316-minimum:0
feature-0-200316-name:property-reporting-state
feature-0-200316-size:1
feature-0-200316-unit-expo:0
feature-0-200316-units:25
feature-0-200316-value:1
How to enable such sensor?
^^^^^^^^^^^^^^^^^^^^^^^^^^
By default sensor can be power gated. To enable sysfs attribute "enable" can be
used.
$ echo 1 > enable_sensor
used::
$ echo 1 > enable_sensor
Once enabled and powered on, sensor can report value using HID reports.
These reports are pushed using misc device interface in a FIFO order.
/dev$ tree | grep HID-SENSOR-2000e1.6.auto
??????? ????????? 10:53 -> ../HID-SENSOR-2000e1.6.auto
????????? HID-SENSOR-2000e1.6.auto
These reports are pushed using misc device interface in a FIFO order::
/dev$ tree | grep HID-SENSOR-2000e1.6.auto
│   │   │   ├── 10:53 -> ../HID-SENSOR-2000e1.6.auto
│   ├── HID-SENSOR-2000e1.6.auto
Each reports can be of variable length preceded by a header. This header
consist of a 32 bit usage id, 64 bit time stamp and 32 bit length field of raw

82
Documentation/hid/hid-transport.txt → Documentation/hid/hid-transport.rst
Просмотреть файл

@ -1,5 +1,6 @@
HID I/O Transport Drivers
===========================
=========================
HID I/O Transport Drivers
=========================
The HID subsystem is independent of the underlying transport driver. Initially,
only USB was supported, but other specifications adopted the HID design and
@ -16,6 +17,8 @@ transport and device setup/management. HID core is responsible of
report-parsing, report interpretation and the user-space API. Device specifics
and quirks are handled by all layers depending on the quirk.
::
+-----------+ +-----------+ +-----------+ +-----------+
| Device #1 | | Device #i | | Device #j | | Device #k |
+-----------+ +-----------+ +-----------+ +-----------+
@ -42,8 +45,9 @@ and quirks are handled by all layers depending on the quirk.
+----------------+ +-----------+ +------------------+ +------------------+
Example Drivers:
I/O: USB, I2C, Bluetooth-l2cap
Transport: USB-HID, I2C-HID, BT-HIDP
- I/O: USB, I2C, Bluetooth-l2cap
- Transport: USB-HID, I2C-HID, BT-HIDP
Everything below "HID Core" is simplified in this graph as it is only of
interest to HID device drivers. Transport drivers do not need to know the
@ -183,7 +187,7 @@ Other ctrl-channel requests are supported by USB-HID but are not available
-------------------
Transport drivers normally use the following procedure to register a new device
with HID core:
with HID core::
struct hid_device *hid;
int ret;
@ -215,7 +219,7 @@ Once hid_add_device() is entered, HID core might use the callbacks provided in
"custom_ll_driver". Note that fields like "country" can be ignored by underlying
transport-drivers if not supported.
To unregister a device, use:
To unregister a device, use::
hid_destroy_device(hid);
@ -226,73 +230,110 @@ driver callbacks.
-----------------------------
The available HID callbacks are:
- int (*start) (struct hid_device *hdev)
::
int (*start) (struct hid_device *hdev)
Called from HID device drivers once they want to use the device. Transport
drivers can choose to setup their device in this callback. However, normally
devices are already set up before transport drivers register them to HID core
so this is mostly only used by USB-HID.
- void (*stop) (struct hid_device *hdev)
::
void (*stop) (struct hid_device *hdev)
Called from HID device drivers once they are done with a device. Transport
drivers can free any buffers and deinitialize the device. But note that
->start() might be called again if another HID device driver is loaded on the
device.
Transport drivers are free to ignore it and deinitialize devices after they
destroyed them via hid_destroy_device().
- int (*open) (struct hid_device *hdev)
::
int (*open) (struct hid_device *hdev)
Called from HID device drivers once they are interested in data reports.
Usually, while user-space didn't open any input API/etc., device drivers are
not interested in device data and transport drivers can put devices asleep.
However, once ->open() is called, transport drivers must be ready for I/O.
->open() calls are nested for each client that opens the HID device.
- void (*close) (struct hid_device *hdev)
::
void (*close) (struct hid_device *hdev)
Called from HID device drivers after ->open() was called but they are no
longer interested in device reports. (Usually if user-space closed any input
devices of the driver).
Transport drivers can put devices asleep and terminate any I/O of all
->open() calls have been followed by a ->close() call. However, ->start() may
be called again if the device driver is interested in input reports again.
- int (*parse) (struct hid_device *hdev)
::
int (*parse) (struct hid_device *hdev)
Called once during device setup after ->start() has been called. Transport
drivers must read the HID report-descriptor from the device and tell HID core
about it via hid_parse_report().
- int (*power) (struct hid_device *hdev, int level)
::
int (*power) (struct hid_device *hdev, int level)
Called by HID core to give PM hints to transport drivers. Usually this is
analogical to the ->open() and ->close() hints and redundant.
- void (*request) (struct hid_device *hdev, struct hid_report *report,
int reqtype)
::
void (*request) (struct hid_device *hdev, struct hid_report *report,
int reqtype)
Send an HID request on the ctrl channel. "report" contains the report that
should be sent and "reqtype" the request type. Request-type can be
HID_REQ_SET_REPORT or HID_REQ_GET_REPORT.
This callback is optional. If not provided, HID core will assemble a raw
report following the HID specs and send it via the ->raw_request() callback.
The transport driver is free to implement this asynchronously.
- int (*wait) (struct hid_device *hdev)
::
int (*wait) (struct hid_device *hdev)
Used by HID core before calling ->request() again. A transport driver can use
it to wait for any pending requests to complete if only one request is
allowed at a time.
- int (*raw_request) (struct hid_device *hdev, unsigned char reportnum,
__u8 *buf, size_t count, unsigned char rtype,
int reqtype)
::
int (*raw_request) (struct hid_device *hdev, unsigned char reportnum,
__u8 *buf, size_t count, unsigned char rtype,
int reqtype)
Same as ->request() but provides the report as raw buffer. This request shall
be synchronous. A transport driver must not use ->wait() to complete such
requests. This request is mandatory and hid core will reject the device if
it is missing.
- int (*output_report) (struct hid_device *hdev, __u8 *buf, size_t len)
::
int (*output_report) (struct hid_device *hdev, __u8 *buf, size_t len)
Send raw output report via intr channel. Used by some HID device drivers
which require high throughput for outgoing requests on the intr channel. This
must not cause SET_REPORT calls! This must be implemented as asynchronous
output report on the intr channel!
- int (*idle) (struct hid_device *hdev, int report, int idle, int reqtype)
::
int (*idle) (struct hid_device *hdev, int report, int idle, int reqtype)
Perform SET/GET_IDLE request. Only used by USB-HID, do not implement!
2.3) Data Path
@ -314,4 +355,5 @@ transport driver and not passed to hid_input_report().
Acknowledgements to SET_REPORT requests are not of interest to HID core.
----------------------------------------------------
Written 2013, David Herrmann <dh.herrmann@gmail.com>

154
Documentation/hid/hiddev.txt → Documentation/hid/hiddev.rst
Просмотреть файл

@ -1,6 +1,9 @@
================================================
Care and feeding of your Human Interface Devices
================================================
INTRODUCTION
Introduction
============
In addition to the normal input type HID devices, USB also uses the
human interface device protocols for things that are not really human
@ -16,38 +19,40 @@ normalised event interface - see Documentation/input/input.rst
* the hiddev interface, which provides fairly raw HID events
The data flow for a HID event produced by a device is something like
the following :
the following::
usb.c ---> hid-core.c ----> hid-input.c ----> [keyboard/mouse/joystick/event]
|
|
--> hiddev.c ----> POWER / MONITOR CONTROL
--> hiddev.c ----> POWER / MONITOR CONTROL
In addition, other subsystems (apart from USB) can potentially feed
events into the input subsystem, but these have no effect on the hid
device interface.
USING THE HID DEVICE INTERFACE
Using the HID Device Interface
==============================
The hiddev interface is a char interface using the normal USB major,
with the minor numbers starting at 96 and finishing at 111. Therefore,
you need the following commands:
mknod /dev/usb/hiddev0 c 180 96
mknod /dev/usb/hiddev1 c 180 97
mknod /dev/usb/hiddev2 c 180 98
mknod /dev/usb/hiddev3 c 180 99
mknod /dev/usb/hiddev4 c 180 100
mknod /dev/usb/hiddev5 c 180 101
mknod /dev/usb/hiddev6 c 180 102
mknod /dev/usb/hiddev7 c 180 103
mknod /dev/usb/hiddev8 c 180 104
mknod /dev/usb/hiddev9 c 180 105
mknod /dev/usb/hiddev10 c 180 106
mknod /dev/usb/hiddev11 c 180 107
mknod /dev/usb/hiddev12 c 180 108
mknod /dev/usb/hiddev13 c 180 109
mknod /dev/usb/hiddev14 c 180 110
mknod /dev/usb/hiddev15 c 180 111
you need the following commands::
mknod /dev/usb/hiddev0 c 180 96
mknod /dev/usb/hiddev1 c 180 97
mknod /dev/usb/hiddev2 c 180 98
mknod /dev/usb/hiddev3 c 180 99
mknod /dev/usb/hiddev4 c 180 100
mknod /dev/usb/hiddev5 c 180 101
mknod /dev/usb/hiddev6 c 180 102
mknod /dev/usb/hiddev7 c 180 103
mknod /dev/usb/hiddev8 c 180 104
mknod /dev/usb/hiddev9 c 180 105
mknod /dev/usb/hiddev10 c 180 106
mknod /dev/usb/hiddev11 c 180 107
mknod /dev/usb/hiddev12 c 180 108
mknod /dev/usb/hiddev13 c 180 109
mknod /dev/usb/hiddev14 c 180 110
mknod /dev/usb/hiddev15 c 180 111
So you point your hiddev compliant user-space program at the correct
interface for your device, and it all just works.
@ -56,7 +61,9 @@ Assuming that you have a hiddev compliant user-space program, of
course. If you need to write one, read on.
THE HIDDEV API
The HIDDEV API
==============
This description should be read in conjunction with the HID
specification, freely available from http://www.usb.org, and
conveniently linked of http://www.linux-usb.org.
@ -69,12 +76,14 @@ each of which can have one or more "usages". In the hid-core,
each one of these usages has a single signed 32 bit value.
read():
-------
This is the event interface. When the HID device's state changes,
it performs an interrupt transfer containing a report which contains
the changed value. The hid-core.c module parses the report, and
returns to hiddev.c the individual usages that have changed within
the report. In its basic mode, the hiddev will make these individual
usage changes available to the reader using a struct hiddev_event:
usage changes available to the reader using a struct hiddev_event::
struct hiddev_event {
unsigned hid;
@ -90,13 +99,19 @@ behavior of the read() function can be modified using the HIDIOCSFLAG
ioctl() described below.
ioctl():
This is the control interface. There are a number of controls:
ioctl():
--------
HIDIOCGVERSION - int (read)
Gets the version code out of the hiddev driver.
This is the control interface. There are a number of controls:
HIDIOCGVERSION
- int (read)
Gets the version code out of the hiddev driver.
HIDIOCAPPLICATION
- (none)
HIDIOCAPPLICATION - (none)
This ioctl call returns the HID application usage associated with the
hid device. The third argument to ioctl() specifies which application
index to get. This is useful when the device has more than one
@ -104,25 +119,33 @@ application collection. If the index is invalid (greater or equal to
the number of application collections this device has) the ioctl
returns -1. You can find out beforehand how many application
collections the device has from the num_applications field from the
hiddev_devinfo structure.
hiddev_devinfo structure.
HIDIOCGCOLLECTIONINFO
- struct hiddev_collection_info (read/write)
HIDIOCGCOLLECTIONINFO - struct hiddev_collection_info (read/write)
This returns a superset of the information above, providing not only
application collections, but all the collections the device has. It
also returns the level the collection lives in the hierarchy.
The user passes in a hiddev_collection_info struct with the index
field set to the index that should be returned. The ioctl fills in
the other fields. If the index is larger than the last collection
The user passes in a hiddev_collection_info struct with the index
field set to the index that should be returned. The ioctl fills in
the other fields. If the index is larger than the last collection
index, the ioctl returns -1 and sets errno to -EINVAL.
HIDIOCGDEVINFO - struct hiddev_devinfo (read)
HIDIOCGDEVINFO
- struct hiddev_devinfo (read)
Gets a hiddev_devinfo structure which describes the device.
HIDIOCGSTRING - struct hiddev_string_descriptor (read/write)
HIDIOCGSTRING
- struct hiddev_string_descriptor (read/write)
Gets a string descriptor from the device. The caller must fill in the
"index" field to indicate which descriptor should be returned.
HIDIOCINITREPORT - (none)
HIDIOCINITREPORT
- (none)
Instructs the kernel to retrieve all input and feature report values
from the device. At this point, all the usage structures will contain
current values for the device, and will maintain it as the device
@ -130,21 +153,29 @@ changes. Note that the use of this ioctl is unnecessary in general,
since later kernels automatically initialize the reports from the
device at attach time.
HIDIOCGNAME - string (variable length)
HIDIOCGNAME
- string (variable length)
Gets the device name
HIDIOCGREPORT - struct hiddev_report_info (write)
HIDIOCGREPORT
- struct hiddev_report_info (write)
Instructs the kernel to get a feature or input report from the device,
in order to selectively update the usage structures (in contrast to
INITREPORT).
HIDIOCSREPORT - struct hiddev_report_info (write)
HIDIOCSREPORT
- struct hiddev_report_info (write)
Instructs the kernel to send a report to the device. This report can
be filled in by the user through HIDIOCSUSAGE calls (below) to fill in
individual usage values in the report before sending the report in full
to the device.
to the device.
HIDIOCGREPORTINFO
- struct hiddev_report_info (read/write)
HIDIOCGREPORTINFO - struct hiddev_report_info (read/write)
Fills in a hiddev_report_info structure for the user. The report is
looked up by type (input, output or feature) and id, so these fields
must be filled in by the user. The ID can be absolute -- the actual
@ -154,52 +185,67 @@ report_id) for the next report after report_id. Without a-priori
information about report ids, the right way to use this ioctl is to
use the relative IDs above to enumerate the valid IDs. The ioctl
returns non-zero when there is no more next ID. The real report ID is
filled into the returned hiddev_report_info structure.
filled into the returned hiddev_report_info structure.
HIDIOCGFIELDINFO
- struct hiddev_field_info (read/write)
HIDIOCGFIELDINFO - struct hiddev_field_info (read/write)
Returns the field information associated with a report in a
hiddev_field_info structure. The user must fill in report_id and
report_type in this structure, as above. The field_index should also
be filled in, which should be a number from 0 and maxfield-1, as
returned from a previous HIDIOCGREPORTINFO call.
returned from a previous HIDIOCGREPORTINFO call.
HIDIOCGUCODE
- struct hiddev_usage_ref (read/write)
HIDIOCGUCODE - struct hiddev_usage_ref (read/write)
Returns the usage_code in a hiddev_usage_ref structure, given that
given its report type, report id, field index, and index within the
field have already been filled into the structure.
HIDIOCGUSAGE - struct hiddev_usage_ref (read/write)
HIDIOCGUSAGE
- struct hiddev_usage_ref (read/write)
Returns the value of a usage in a hiddev_usage_ref structure. The
usage to be retrieved can be specified as above, or the user can
choose to fill in the report_type field and specify the report_id as
HID_REPORT_ID_UNKNOWN. In this case, the hiddev_usage_ref will be
filled in with the report and field information associated with this
usage if it is found.
usage if it is found.
HIDIOCSUSAGE
- struct hiddev_usage_ref (write)
HIDIOCSUSAGE - struct hiddev_usage_ref (write)
Sets the value of a usage in an output report. The user fills in
the hiddev_usage_ref structure as above, but additionally fills in
the value field.
HIDIOGCOLLECTIONINDEX - struct hiddev_usage_ref (write)
HIDIOGCOLLECTIONINDEX
- struct hiddev_usage_ref (write)
Returns the collection index associated with this usage. This
indicates where in the collection hierarchy this usage sits.
HIDIOCGFLAG - int (read)
HIDIOCSFLAG - int (write)
HIDIOCGFLAG
- int (read)
HIDIOCSFLAG
- int (write)
These operations respectively inspect and replace the mode flags
that influence the read() call above. The flags are as follows:
HIDDEV_FLAG_UREF - read() calls will now return
HIDDEV_FLAG_UREF
- read() calls will now return
struct hiddev_usage_ref instead of struct hiddev_event.
This is a larger structure, but in situations where the
device has more than one usage in its reports with the
same usage code, this mode serves to resolve such
ambiguity.
HIDDEV_FLAG_REPORT - This flag can only be used in conjunction
HIDDEV_FLAG_REPORT
- This flag can only be used in conjunction
with HIDDEV_FLAG_UREF. With this flag set, when the device
sends a report, a struct hiddev_usage_ref will be returned
to read() filled in with the report_type and report_id, but
to read() filled in with the report_type and report_id, but
with field_index set to FIELD_INDEX_NONE. This serves as
additional notification when the device has sent a report.

53
Documentation/hid/hidraw.txt → Documentation/hid/hidraw.rst
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@ -1,5 +1,6 @@
HIDRAW - Raw Access to USB and Bluetooth Human Interface Devices
==================================================================
================================================================
HIDRAW - Raw Access to USB and Bluetooth Human Interface Devices
================================================================
The hidraw driver provides a raw interface to USB and Bluetooth Human
Interface Devices (HIDs). It differs from hiddev in that reports sent and
@ -31,6 +32,7 @@ directly under /dev (eg: /dev/hidraw0). As this location is distribution-
and udev rule-dependent, applications should use libudev to locate hidraw
devices attached to the system. There is a tutorial on libudev with a
working example at:
http://www.signal11.us/oss/udev/
The HIDRAW API
@ -51,7 +53,7 @@ byte. For devices which do not use numbered reports, the report data
will begin at the first byte.
write()
--------
-------
The write() function will write a report to the device. For USB devices, if
the device has an INTERRUPT OUT endpoint, the report will be sent on that
endpoint. If it does not, the report will be sent over the control endpoint,
@ -62,38 +64,52 @@ number. If the device does not use numbered reports, the first byte should
be set to 0. The report data itself should begin at the second byte.
ioctl()
--------
-------
Hidraw supports the following ioctls:
HIDIOCGRDESCSIZE: Get Report Descriptor Size
HIDIOCGRDESCSIZE:
Get Report Descriptor Size
This ioctl will get the size of the device's report descriptor.
HIDIOCGRDESC: Get Report Descriptor
HIDIOCGRDESC:
Get Report Descriptor
This ioctl returns the device's report descriptor using a
hidraw_report_descriptor struct. Make sure to set the size field of the
hidraw_report_descriptor struct to the size returned from HIDIOCGRDESCSIZE.
HIDIOCGRAWINFO: Get Raw Info
HIDIOCGRAWINFO:
Get Raw Info
This ioctl will return a hidraw_devinfo struct containing the bus type, the
vendor ID (VID), and product ID (PID) of the device. The bus type can be one
of:
BUS_USB
BUS_HIL
BUS_BLUETOOTH
BUS_VIRTUAL
of::
- BUS_USB
- BUS_HIL
- BUS_BLUETOOTH
- BUS_VIRTUAL
which are defined in uapi/linux/input.h.
HIDIOCGRAWNAME(len): Get Raw Name
HIDIOCGRAWNAME(len):
Get Raw Name
This ioctl returns a string containing the vendor and product strings of
the device. The returned string is Unicode, UTF-8 encoded.
HIDIOCGRAWPHYS(len): Get Physical Address
HIDIOCGRAWPHYS(len):
Get Physical Address
This ioctl returns a string representing the physical address of the device.
For USB devices, the string contains the physical path to the device (the
USB controller, hubs, ports, etc). For Bluetooth devices, the string
contains the hardware (MAC) address of the device.
HIDIOCSFEATURE(len): Send a Feature Report
HIDIOCSFEATURE(len):
Send a Feature Report
This ioctl will send a feature report to the device. Per the HID
specification, feature reports are always sent using the control endpoint.
Set the first byte of the supplied buffer to the report number. For devices
@ -101,7 +117,9 @@ which do not use numbered reports, set the first byte to 0. The report data
begins in the second byte. Make sure to set len accordingly, to one more
than the length of the report (to account for the report number).
HIDIOCGFEATURE(len): Get a Feature Report
HIDIOCGFEATURE(len):
Get a Feature Report
This ioctl will request a feature report from the device using the control
endpoint. The first byte of the supplied buffer should be set to the report
number of the requested report. For devices which do not use numbered
@ -109,11 +127,12 @@ reports, set the first byte to 0. The report will be returned starting at
the first byte of the buffer (ie: the report number is not returned).
Example
---------
-------
In samples/, find hid-example.c, which shows examples of read(), write(),
and all the ioctls for hidraw. The code may be used by anyone for any
purpose, and can serve as a starting point for developing applications using
hidraw.
Document by:
Alan Ott <alan@signal11.us>, Signal 11 Software

18
Documentation/hid/index.rst Normal file
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@ -0,0 +1,18 @@
:orphan:
=============================
Human Interface Devices (HID)
=============================
.. toctree::
:maxdepth: 1
hiddev
hidraw
hid-sensor
hid-transport
uhid
hid-alps
intel-ish-hid

485
Documentation/hid/intel-ish-hid.rst Normal file
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@ -0,0 +1,485 @@
=================================
Intel Integrated Sensor Hub (ISH)
=================================
A sensor hub enables the ability to offload sensor polling and algorithm
processing to a dedicated low power co-processor. This allows the core
processor to go into low power modes more often, resulting in the increased
battery life.
There are many vendors providing external sensor hubs confirming to HID
Sensor usage tables, and used in several tablets, 2 in 1 convertible laptops
and embedded products. Linux had this support since Linux 3.9.
Intel® introduced integrated sensor hubs as a part of the SoC starting from
Cherry Trail and now supported on multiple generations of CPU packages. There
are many commercial devices already shipped with Integrated Sensor Hubs (ISH).
These ISH also comply to HID sensor specification, but the difference is the
transport protocol used for communication. The current external sensor hubs
mainly use HID over i2C or USB. But ISH doesn't use either i2c or USB.
1. Overview
===========
Using a analogy with a usbhid implementation, the ISH follows a similar model
for a very high speed communication::
----------------- ----------------------
| USB HID | --> | ISH HID |
----------------- ----------------------
----------------- ----------------------
| USB protocol | --> | ISH Transport |
----------------- ----------------------
----------------- ----------------------
| EHCI/XHCI | --> | ISH IPC |
----------------- ----------------------
PCI PCI
----------------- ----------------------
|Host controller| --> | ISH processor |
----------------- ----------------------
USB Link
----------------- ----------------------
| USB End points| --> | ISH Clients |
----------------- ----------------------
Like USB protocol provides a method for device enumeration, link management
and user data encapsulation, the ISH also provides similar services. But it is
very light weight tailored to manage and communicate with ISH client
applications implemented in the firmware.
The ISH allows multiple sensor management applications executing in the
firmware. Like USB endpoints the messaging can be to/from a client. As part of
enumeration process, these clients are identified. These clients can be simple
HID sensor applications, sensor calibration application or senor firmware
update application.
The implementation model is similar, like USB bus, ISH transport is also
implemented as a bus. Each client application executing in the ISH processor
is registered as a device on this bus. The driver, which binds each device
(ISH HID driver) identifies the device type and registers with the hid core.
2. ISH Implementation: Block Diagram
====================================
::
---------------------------
| User Space Applications |
---------------------------
----------------IIO ABI----------------
--------------------------
| IIO Sensor Drivers |
--------------------------
--------------------------
| IIO core |
--------------------------
--------------------------
| HID Sensor Hub MFD |
--------------------------
--------------------------
| HID Core |
--------------------------
--------------------------
| HID over ISH Client |
--------------------------
--------------------------
| ISH Transport (ISHTP) |
--------------------------
--------------------------
| IPC Drivers |
--------------------------
OS
---------------- PCI -----------------
Hardware + Firmware
----------------------------
| ISH Hardware/Firmware(FW) |
----------------------------
3. High level processing in above blocks
========================================
3.1 Hardware Interface
----------------------
The ISH is exposed as "Non-VGA unclassified PCI device" to the host. The PCI
product and vendor IDs are changed from different generations of processors. So
the source code which enumerate drivers needs to update from generation to
generation.
3.2 Inter Processor Communication (IPC) driver
----------------------------------------------
Location: drivers/hid/intel-ish-hid/ipc
The IPC message used memory mapped I/O. The registers are defined in
hw-ish-regs.h.
3.2.1 IPC/FW message types
^^^^^^^^^^^^^^^^^^^^^^^^^^
There are two types of messages, one for management of link and other messages
are to and from transport layers.
TX and RX of Transport messages
...............................
A set of memory mapped register offers support of multi byte messages TX and
RX (E.g.IPC_REG_ISH2HOST_MSG, IPC_REG_HOST2ISH_MSG). The IPC layer maintains
internal queues to sequence messages and send them in order to the FW.
Optionally the caller can register handler to get notification of completion.
A door bell mechanism is used in messaging to trigger processing in host and
client firmware side. When ISH interrupt handler is called, the ISH2HOST
doorbell register is used by host drivers to determine that the interrupt
is for ISH.
Each side has 32 32-bit message registers and a 32-bit doorbell. Doorbell
register has the following format:
Bits 0..6: fragment length (7 bits are used)
Bits 10..13: encapsulated protocol
Bits 16..19: management command (for IPC management protocol)
Bit 31: doorbell trigger (signal H/W interrupt to the other side)
Other bits are reserved, should be 0.
3.2.2 Transport layer interface
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
To abstract HW level IPC communication, a set of callbacks are registered.
The transport layer uses them to send and receive messages.
Refer to struct ishtp_hw_ops for callbacks.
3.3 ISH Transport layer
-----------------------
Location: drivers/hid/intel-ish-hid/ishtp/
3.3.1 A Generic Transport Layer
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The transport layer is a bi-directional protocol, which defines:
- Set of commands to start, stop, connect, disconnect and flow control
(ishtp/hbm.h) for details
- A flow control mechanism to avoid buffer overflows
This protocol resembles bus messages described in the following document:
http://www.intel.com/content/dam/www/public/us/en/documents/technical-\
specifications/dcmi-hi-1-0-spec.pdf "Chapter 7: Bus Message Layer"
3.3.2 Connection and Flow Control Mechanism
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Each FW client and a protocol is identified by an UUID. In order to communicate
to a FW client, a connection must be established using connect request and
response bus messages. If successful, a pair (host_client_id and fw_client_id)
will identify the connection.
Once connection is established, peers send each other flow control bus messages
independently. Every peer may send a message only if it has received a
flow-control credit before. Once it sent a message, it may not send another one
before receiving the next flow control credit.
Either side can send disconnect request bus message to end communication. Also
the link will be dropped if major FW reset occurs.
3.3.3 Peer to Peer data transfer
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Peer to Peer data transfer can happen with or without using DMA. Depending on
the sensor bandwidth requirement DMA can be enabled by using module parameter
ishtp_use_dma under intel_ishtp.
Each side (host and FW) manages its DMA transfer memory independently. When an
ISHTP client from either host or FW side wants to send something, it decides
whether to send over IPC or over DMA; for each transfer the decision is
independent. The sending side sends DMA_XFER message when the message is in
the respective host buffer (TX when host client sends, RX when FW client
sends). The recipient of DMA message responds with DMA_XFER_ACK, indicating
the sender that the memory region for that message may be reused.
DMA initialization is started with host sending DMA_ALLOC_NOTIFY bus message
(that includes RX buffer) and FW responds with DMA_ALLOC_NOTIFY_ACK.
Additionally to DMA address communication, this sequence checks capabilities:
if thw host doesn't support DMA, then it won't send DMA allocation, so FW can't
send DMA; if FW doesn't support DMA then it won't respond with
DMA_ALLOC_NOTIFY_ACK, in which case host will not use DMA transfers.
Here ISH acts as busmaster DMA controller. Hence when host sends DMA_XFER,
it's request to do host->ISH DMA transfer; when FW sends DMA_XFER, it means
that it already did DMA and the message resides at host. Thus, DMA_XFER
and DMA_XFER_ACK act as ownership indicators.
At initial state all outgoing memory belongs to the sender (TX to host, RX to
FW), DMA_XFER transfers ownership on the region that contains ISHTP message to
the receiving side, DMA_XFER_ACK returns ownership to the sender. A sender
needs not wait for previous DMA_XFER to be ack'ed, and may send another message
as long as remaining continuous memory in its ownership is enough.
In principle, multiple DMA_XFER and DMA_XFER_ACK messages may be sent at once
(up to IPC MTU), thus allowing for interrupt throttling.
Currently, ISH FW decides to send over DMA if ISHTP message is more than 3 IPC
fragments and via IPC otherwise.
3.3.4 Ring Buffers
^^^^^^^^^^^^^^^^^^
When a client initiate a connection, a ring or RX and TX buffers are allocated.
The size of ring can be specified by the client. HID client set 16 and 32 for
TX and RX buffers respectively. On send request from client, the data to be
sent is copied to one of the send ring buffer and scheduled to be sent using
bus message protocol. These buffers are required because the FW may have not
have processed the last message and may not have enough flow control credits
to send. Same thing holds true on receive side and flow control is required.
3.3.5 Host Enumeration
^^^^^^^^^^^^^^^^^^^^^^
The host enumeration bus command allow discovery of clients present in the FW.
There can be multiple sensor clients and clients for calibration function.
To ease in implantation and allow independent driver handle each client
this transport layer takes advantage of Linux Bus driver model. Each
client is registered as device on the the transport bus (ishtp bus).
Enumeration sequence of messages:
- Host sends HOST_START_REQ_CMD, indicating that host ISHTP layer is up.
- FW responds with HOST_START_RES_CMD
- Host sends HOST_ENUM_REQ_CMD (enumerate FW clients)
- FW responds with HOST_ENUM_RES_CMD that includes bitmap of available FW
client IDs
- For each FW ID found in that bitmap host sends
HOST_CLIENT_PROPERTIES_REQ_CMD
- FW responds with HOST_CLIENT_PROPERTIES_RES_CMD. Properties include UUID,
max ISHTP message size, etc.
- Once host received properties for that last discovered client, it considers
ISHTP device fully functional (and allocates DMA buffers)
3.4 HID over ISH Client
-----------------------
Location: drivers/hid/intel-ish-hid
The ISHTP client driver is responsible for:
- enumerate HID devices under FW ISH client
- Get Report descriptor
- Register with HID core as a LL driver
- Process Get/Set feature request
- Get input reports
3.5 HID Sensor Hub MFD and IIO sensor drivers
---------------------------------------------
The functionality in these drivers is the same as an external sensor hub.
Refer to
Documentation/hid/hid-sensor.rst for HID sensor
Documentation/ABI/testing/sysfs-bus-iio for IIO ABIs to user space
3.6 End to End HID transport Sequence Diagram
---------------------------------------------
::
HID-ISH-CLN ISHTP IPC HW
| | | |
| | |-----WAKE UP------------------>|
| | | |
| | |-----HOST READY--------------->|
| | | |
| | |<----MNG_RESET_NOTIFY_ACK----- |
| | | |
| |<----ISHTP_START------ | |
| | | |
| |<-----------------HOST_START_RES_CMD-------------------|
| | | |
| |------------------QUERY_SUBSCRIBER-------------------->|
| | | |
| |------------------HOST_ENUM_REQ_CMD------------------->|
| | | |
| |<-----------------HOST_ENUM_RES_CMD--------------------|
| | | |
| |------------------HOST_CLIENT_PROPERTIES_REQ_CMD------>|
| | | |
| |<-----------------HOST_CLIENT_PROPERTIES_RES_CMD-------|
| Create new device on in ishtp bus | |
| | | |
| |------------------HOST_CLIENT_PROPERTIES_REQ_CMD------>|
| | | |
| |<-----------------HOST_CLIENT_PROPERTIES_RES_CMD-------|
| Create new device on in ishtp bus | |
| | | |
| |--Repeat HOST_CLIENT_PROPERTIES_REQ_CMD-till last one--|
| | | |
probed()
|----ishtp_cl_connect--->|----------------- CLIENT_CONNECT_REQ_CMD-------------->|
| | | |
| |<----------------CLIENT_CONNECT_RES_CMD----------------|
| | | |
|register event callback | | |
| | | |
|ishtp_cl_send(
HOSTIF_DM_ENUM_DEVICES) |----------fill ishtp_msg_hdr struct write to HW----- >|
| | | |
| | |<-----IRQ(IPC_PROTOCOL_ISHTP---|
| | | |
|<--ENUM_DEVICE RSP------| | |
| | | |
for each enumerated device
|ishtp_cl_send(
HOSTIF_GET_HID_DESCRIPTOR|----------fill ishtp_msg_hdr struct write to HW----- >|
| | | |
...Response
| | | |
for each enumerated device
|ishtp_cl_send(
HOSTIF_GET_REPORT_DESCRIPTOR|--------------fill ishtp_msg_hdr struct write to HW-- >|
| | | |
| | | |
hid_allocate_device
| | | |
hid_add_device | | |
| | | |
3.7 ISH Debugging
-----------------
To debug ISH, event tracing mechanism is used. To enable debug logs
echo 1 > /sys/kernel/debug/tracing/events/intel_ish/enable
cat sys/kernel/debug/tracing/trace
3.8 ISH IIO sysfs Example on Lenovo thinkpad Yoga 260
-----------------------------------------------------
::
root@otcpl-ThinkPad-Yoga-260:~# tree -l /sys/bus/iio/devices/
/sys/bus/iio/devices/
├── iio:device0 -> ../../../devices/0044:8086:22D8.0001/HID-SENSOR-200073.9.auto/iio:device0
│   ├── buffer
│   │   ├── enable
│   │   ├── length
│   │   └── watermark
...
│   ├── in_accel_hysteresis
│   ├── in_accel_offset
│   ├── in_accel_sampling_frequency
│   ├── in_accel_scale
│   ├── in_accel_x_raw
│   ├── in_accel_y_raw
│   ├── in_accel_z_raw
│   ├── name
│   ├── scan_elements
│   │   ├── in_accel_x_en
│   │   ├── in_accel_x_index
│   │   ├── in_accel_x_type
│   │   ├── in_accel_y_en
│   │   ├── in_accel_y_index
│   │   ├── in_accel_y_type
│   │   ├── in_accel_z_en
│   │   ├── in_accel_z_index
│   │   └── in_accel_z_type
...
│   │   ├── devices
│   │   │   │   ├── buffer
│   │   │   │   │   ├── enable
│   │   │   │   │   ├── length
│   │   │   │   │   └── watermark
│   │   │   │   ├── dev
│   │   │   │   ├── in_intensity_both_raw
│   │   │   │   ├── in_intensity_hysteresis
│   │   │   │   ├── in_intensity_offset
│   │   │   │   ├── in_intensity_sampling_frequency
│   │   │   │   ├── in_intensity_scale
│   │   │   │   ├── name
│   │   │   │   ├── scan_elements
│   │   │   │   │   ├── in_intensity_both_en
│   │   │   │   │   ├── in_intensity_both_index
│   │   │   │   │   └── in_intensity_both_type
│   │   │   │   ├── trigger
│   │   │   │   │   └── current_trigger
...
│   │   │   │   ├── buffer
│   │   │   │   │   ├── enable
│   │   │   │   │   ├── length
│   │   │   │   │   └── watermark
│   │   │   │   ├── dev
│   │   │   │   ├── in_magn_hysteresis
│   │   │   │   ├── in_magn_offset
│   │   │   │   ├── in_magn_sampling_frequency
│   │   │   │   ├── in_magn_scale
│   │   │   │   ├── in_magn_x_raw
│   │   │   │   ├── in_magn_y_raw
│   │   │   │   ├── in_magn_z_raw
│   │   │   │   ├── in_rot_from_north_magnetic_tilt_comp_raw
│   │   │   │   ├── in_rot_hysteresis
│   │   │   │   ├── in_rot_offset
│   │   │   │   ├── in_rot_sampling_frequency
│   │   │   │   ├── in_rot_scale
│   │   │   │   ├── name
...
│   │   │   │   ├── scan_elements
│   │   │   │   │   ├── in_magn_x_en
│   │   │   │   │   ├── in_magn_x_index
│   │   │   │   │   ├── in_magn_x_type
│   │   │   │   │   ├── in_magn_y_en
│   │   │   │   │   ├── in_magn_y_index
│   │   │   │   │   ├── in_magn_y_type
│   │   │   │   │   ├── in_magn_z_en
│   │   │   │   │   ├── in_magn_z_index
│   │   │   │   │   ├── in_magn_z_type
│   │   │   │   │   ├── in_rot_from_north_magnetic_tilt_comp_en
│   │   │   │   │   ├── in_rot_from_north_magnetic_tilt_comp_index
│   │   │   │   │   └── in_rot_from_north_magnetic_tilt_comp_type
│   │   │   │   ├── trigger
│   │   │   │   │   └── current_trigger
...
│   │   │   │   ├── buffer
│   │   │   │   │   ├── enable
│   │   │   │   │   ├── length
│   │   │   │   │   └── watermark
│   │   │   │   ├── dev
│   │   │   │   ├── in_anglvel_hysteresis
│   │   │   │   ├── in_anglvel_offset
│   │   │   │   ├── in_anglvel_sampling_frequency
│   │   │   │   ├── in_anglvel_scale
│   │   │   │   ├── in_anglvel_x_raw
│   │   │   │   ├── in_anglvel_y_raw
│   │   │   │   ├── in_anglvel_z_raw
│   │   │   │   ├── name
│   │   │   │   ├── scan_elements
│   │   │   │   │   ├── in_anglvel_x_en
│   │   │   │   │   ├── in_anglvel_x_index
│   │   │   │   │   ├── in_anglvel_x_type
│   │   │   │   │   ├── in_anglvel_y_en
│   │   │   │   │   ├── in_anglvel_y_index
│   │   │   │   │   ├── in_anglvel_y_type
│   │   │   │   │   ├── in_anglvel_z_en
│   │   │   │   │   ├── in_anglvel_z_index
│   │   │   │   │   └── in_anglvel_z_type
│   │   │   │   ├── trigger
│   │   │   │   │   └── current_trigger
...
│   │   │   │   ├── buffer
│   │   │   │   │   ├── enable
│   │   │   │   │   ├── length
│   │   │   │   │   └── watermark
│   │   │   │   ├── dev
│   │   │   │   ├── in_anglvel_hysteresis
│   │   │   │   ├── in_anglvel_offset
│   │   │   │   ├── in_anglvel_sampling_frequency
│   │   │   │   ├── in_anglvel_scale
│   │   │   │   ├── in_anglvel_x_raw
│   │   │   │   ├── in_anglvel_y_raw
│   │   │   │   ├── in_anglvel_z_raw
│   │   │   │   ├── name
│   │   │   │   ├── scan_elements
│   │   │   │   │   ├── in_anglvel_x_en
│   │   │   │   │   ├── in_anglvel_x_index
│   │   │   │   │   ├── in_anglvel_x_type
│   │   │   │   │   ├── in_anglvel_y_en
│   │   │   │   │   ├── in_anglvel_y_index
│   │   │   │   │   ├── in_anglvel_y_type
│   │   │   │   │   ├── in_anglvel_z_en
│   │   │   │   │   ├── in_anglvel_z_index
│   │   │   │   │   └── in_anglvel_z_type
│   │   │   │   ├── trigger
│   │   │   │   │   └── current_trigger
...

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Intel Integrated Sensor Hub (ISH)
===============================
A sensor hub enables the ability to offload sensor polling and algorithm
processing to a dedicated low power co-processor. This allows the core
processor to go into low power modes more often, resulting in the increased
battery life.
There are many vendors providing external sensor hubs confirming to HID
Sensor usage tables, and used in several tablets, 2 in 1 convertible laptops
and embedded products. Linux had this support since Linux 3.9.
Intel® introduced integrated sensor hubs as a part of the SoC starting from
Cherry Trail and now supported on multiple generations of CPU packages. There
are many commercial devices already shipped with Integrated Sensor Hubs (ISH).
These ISH also comply to HID sensor specification, but the difference is the
transport protocol used for communication. The current external sensor hubs
mainly use HID over i2C or USB. But ISH doesn't use either i2c or USB.
1. Overview
Using a analogy with a usbhid implementation, the ISH follows a similar model
for a very high speed communication:
----------------- ----------------------
| USB HID | --> | ISH HID |
----------------- ----------------------
----------------- ----------------------
| USB protocol | --> | ISH Transport |
----------------- ----------------------
----------------- ----------------------
| EHCI/XHCI | --> | ISH IPC |
----------------- ----------------------
PCI PCI
----------------- ----------------------
|Host controller| --> | ISH processor |
----------------- ----------------------
USB Link
----------------- ----------------------
| USB End points| --> | ISH Clients |
----------------- ----------------------
Like USB protocol provides a method for device enumeration, link management
and user data encapsulation, the ISH also provides similar services. But it is
very light weight tailored to manage and communicate with ISH client
applications implemented in the firmware.
The ISH allows multiple sensor management applications executing in the
firmware. Like USB endpoints the messaging can be to/from a client. As part of
enumeration process, these clients are identified. These clients can be simple
HID sensor applications, sensor calibration application or senor firmware
update application.
The implementation model is similar, like USB bus, ISH transport is also
implemented as a bus. Each client application executing in the ISH processor
is registered as a device on this bus. The driver, which binds each device
(ISH HID driver) identifies the device type and registers with the hid core.
2. ISH Implementation: Block Diagram
---------------------------
| User Space Applications |
---------------------------
----------------IIO ABI----------------
--------------------------
| IIO Sensor Drivers |
--------------------------
--------------------------
| IIO core |
--------------------------
--------------------------
| HID Sensor Hub MFD |
--------------------------
--------------------------
| HID Core |
--------------------------
--------------------------
| HID over ISH Client |
--------------------------
--------------------------
| ISH Transport (ISHTP) |
--------------------------
--------------------------
| IPC Drivers |
--------------------------
OS
---------------- PCI -----------------
Hardware + Firmware
----------------------------
| ISH Hardware/Firmware(FW) |
----------------------------
3. High level processing in above blocks
3.1 Hardware Interface
The ISH is exposed as "Non-VGA unclassified PCI device" to the host. The PCI
product and vendor IDs are changed from different generations of processors. So
the source code which enumerate drivers needs to update from generation to
generation.
3.2 Inter Processor Communication (IPC) driver
Location: drivers/hid/intel-ish-hid/ipc
The IPC message used memory mapped I/O. The registers are defined in
hw-ish-regs.h.
3.2.1 IPC/FW message types
There are two types of messages, one for management of link and other messages
are to and from transport layers.
TX and RX of Transport messages
A set of memory mapped register offers support of multi byte messages TX and
RX (E.g.IPC_REG_ISH2HOST_MSG, IPC_REG_HOST2ISH_MSG). The IPC layer maintains
internal queues to sequence messages and send them in order to the FW.
Optionally the caller can register handler to get notification of completion.
A door bell mechanism is used in messaging to trigger processing in host and
client firmware side. When ISH interrupt handler is called, the ISH2HOST
doorbell register is used by host drivers to determine that the interrupt
is for ISH.
Each side has 32 32-bit message registers and a 32-bit doorbell. Doorbell
register has the following format:
Bits 0..6: fragment length (7 bits are used)
Bits 10..13: encapsulated protocol
Bits 16..19: management command (for IPC management protocol)
Bit 31: doorbell trigger (signal H/W interrupt to the other side)
Other bits are reserved, should be 0.
3.2.2 Transport layer interface
To abstract HW level IPC communication, a set of callbacks are registered.
The transport layer uses them to send and receive messages.
Refer to struct ishtp_hw_ops for callbacks.
3.3 ISH Transport layer
Location: drivers/hid/intel-ish-hid/ishtp/
3.3.1 A Generic Transport Layer
The transport layer is a bi-directional protocol, which defines:
- Set of commands to start, stop, connect, disconnect and flow control
(ishtp/hbm.h) for details
- A flow control mechanism to avoid buffer overflows
This protocol resembles bus messages described in the following document:
http://www.intel.com/content/dam/www/public/us/en/documents/technical-\
specifications/dcmi-hi-1-0-spec.pdf "Chapter 7: Bus Message Layer"
3.3.2 Connection and Flow Control Mechanism
Each FW client and a protocol is identified by an UUID. In order to communicate
to a FW client, a connection must be established using connect request and
response bus messages. If successful, a pair (host_client_id and fw_client_id)
will identify the connection.
Once connection is established, peers send each other flow control bus messages
independently. Every peer may send a message only if it has received a
flow-control credit before. Once it sent a message, it may not send another one
before receiving the next flow control credit.
Either side can send disconnect request bus message to end communication. Also
the link will be dropped if major FW reset occurs.
3.3.3 Peer to Peer data transfer
Peer to Peer data transfer can happen with or without using DMA. Depending on
the sensor bandwidth requirement DMA can be enabled by using module parameter
ishtp_use_dma under intel_ishtp.
Each side (host and FW) manages its DMA transfer memory independently. When an
ISHTP client from either host or FW side wants to send something, it decides
whether to send over IPC or over DMA; for each transfer the decision is
independent. The sending side sends DMA_XFER message when the message is in
the respective host buffer (TX when host client sends, RX when FW client
sends). The recipient of DMA message responds with DMA_XFER_ACK, indicating
the sender that the memory region for that message may be reused.
DMA initialization is started with host sending DMA_ALLOC_NOTIFY bus message
(that includes RX buffer) and FW responds with DMA_ALLOC_NOTIFY_ACK.
Additionally to DMA address communication, this sequence checks capabilities:
if thw host doesn't support DMA, then it won't send DMA allocation, so FW can't
send DMA; if FW doesn't support DMA then it won't respond with
DMA_ALLOC_NOTIFY_ACK, in which case host will not use DMA transfers.
Here ISH acts as busmaster DMA controller. Hence when host sends DMA_XFER,
it's request to do host->ISH DMA transfer; when FW sends DMA_XFER, it means
that it already did DMA and the message resides at host. Thus, DMA_XFER
and DMA_XFER_ACK act as ownership indicators.
At initial state all outgoing memory belongs to the sender (TX to host, RX to
FW), DMA_XFER transfers ownership on the region that contains ISHTP message to
the receiving side, DMA_XFER_ACK returns ownership to the sender. A sender
needs not wait for previous DMA_XFER to be ack'ed, and may send another message
as long as remaining continuous memory in its ownership is enough.
In principle, multiple DMA_XFER and DMA_XFER_ACK messages may be sent at once
(up to IPC MTU), thus allowing for interrupt throttling.
Currently, ISH FW decides to send over DMA if ISHTP message is more than 3 IPC
fragments and via IPC otherwise.
3.3.4 Ring Buffers
When a client initiate a connection, a ring or RX and TX buffers are allocated.
The size of ring can be specified by the client. HID client set 16 and 32 for
TX and RX buffers respectively. On send request from client, the data to be
sent is copied to one of the send ring buffer and scheduled to be sent using
bus message protocol. These buffers are required because the FW may have not
have processed the last message and may not have enough flow control credits
to send. Same thing holds true on receive side and flow control is required.
3.3.5 Host Enumeration
The host enumeration bus command allow discovery of clients present in the FW.
There can be multiple sensor clients and clients for calibration function.
To ease in implantation and allow independent driver handle each client
this transport layer takes advantage of Linux Bus driver model. Each
client is registered as device on the the transport bus (ishtp bus).
Enumeration sequence of messages:
- Host sends HOST_START_REQ_CMD, indicating that host ISHTP layer is up.
- FW responds with HOST_START_RES_CMD
- Host sends HOST_ENUM_REQ_CMD (enumerate FW clients)
- FW responds with HOST_ENUM_RES_CMD that includes bitmap of available FW
client IDs
- For each FW ID found in that bitmap host sends
HOST_CLIENT_PROPERTIES_REQ_CMD
- FW responds with HOST_CLIENT_PROPERTIES_RES_CMD. Properties include UUID,
max ISHTP message size, etc.
- Once host received properties for that last discovered client, it considers
ISHTP device fully functional (and allocates DMA buffers)
3.4 HID over ISH Client
Location: drivers/hid/intel-ish-hid
The ISHTP client driver is responsible for:
- enumerate HID devices under FW ISH client
- Get Report descriptor
- Register with HID core as a LL driver
- Process Get/Set feature request
- Get input reports
3.5 HID Sensor Hub MFD and IIO sensor drivers
The functionality in these drivers is the same as an external sensor hub.
Refer to
Documentation/hid/hid-sensor.txt for HID sensor
Documentation/ABI/testing/sysfs-bus-iio for IIO ABIs to user space
3.6 End to End HID transport Sequence Diagram
HID-ISH-CLN ISHTP IPC HW
| | | |
| | |-----WAKE UP------------------>|
| | | |
| | |-----HOST READY--------------->|
| | | |
| | |<----MNG_RESET_NOTIFY_ACK----- |
| | | |
| |<----ISHTP_START------ | |
| | | |
| |<-----------------HOST_START_RES_CMD-------------------|
| | | |
| |------------------QUERY_SUBSCRIBER-------------------->|
| | | |
| |------------------HOST_ENUM_REQ_CMD------------------->|
| | | |
| |<-----------------HOST_ENUM_RES_CMD--------------------|
| | | |
| |------------------HOST_CLIENT_PROPERTIES_REQ_CMD------>|
| | | |
| |<-----------------HOST_CLIENT_PROPERTIES_RES_CMD-------|
| Create new device on in ishtp bus | |
| | | |
| |------------------HOST_CLIENT_PROPERTIES_REQ_CMD------>|
| | | |
| |<-----------------HOST_CLIENT_PROPERTIES_RES_CMD-------|
| Create new device on in ishtp bus | |
| | | |
| |--Repeat HOST_CLIENT_PROPERTIES_REQ_CMD-till last one--|
| | | |
probed()
|----ishtp_cl_connect-->|----------------- CLIENT_CONNECT_REQ_CMD-------------->|
| | | |
| |<----------------CLIENT_CONNECT_RES_CMD----------------|
| | | |
|register event callback| | |
| | | |
|ishtp_cl_send(
HOSTIF_DM_ENUM_DEVICES) |----------fill ishtp_msg_hdr struct write to HW----- >|
| | | |
| | |<-----IRQ(IPC_PROTOCOL_ISHTP---|
| | | |
|<--ENUM_DEVICE RSP-----| | |
| | | |
for each enumerated device
|ishtp_cl_send(
HOSTIF_GET_HID_DESCRIPTOR |----------fill ishtp_msg_hdr struct write to HW--- >|
| | | |
...Response
| | | |
for each enumerated device
|ishtp_cl_send(
HOSTIF_GET_REPORT_DESCRIPTOR |----------fill ishtp_msg_hdr struct write to HW- >|
| | | |
| | | |
hid_allocate_device
| | | |
hid_add_device | | |
| | | |
3.7 ISH Debugging
To debug ISH, event tracing mechanism is used. To enable debug logs
echo 1 > /sys/kernel/debug/tracing/events/intel_ish/enable
cat sys/kernel/debug/tracing/trace
3.8 ISH IIO sysfs Example on Lenovo thinkpad Yoga 260
root@otcpl-ThinkPad-Yoga-260:~# tree -l /sys/bus/iio/devices/
/sys/bus/iio/devices/
├── iio:device0 -> ../../../devices/0044:8086:22D8.0001/HID-SENSOR-200073.9.auto/iio:device0
│   ├── buffer
│   │   ├── enable
│   │   ├── length
│   │   └── watermark
...
│   ├── in_accel_hysteresis
│   ├── in_accel_offset
│   ├── in_accel_sampling_frequency
│   ├── in_accel_scale
│   ├── in_accel_x_raw
│   ├── in_accel_y_raw
│   ├── in_accel_z_raw
│   ├── name
│   ├── scan_elements
│   │   ├── in_accel_x_en
│   │   ├── in_accel_x_index
│   │   ├── in_accel_x_type
│   │   ├── in_accel_y_en
│   │   ├── in_accel_y_index
│   │   ├── in_accel_y_type
│   │   ├── in_accel_z_en
│   │   ├── in_accel_z_index
│   │   └── in_accel_z_type
...
│   │   ├── devices
│   │   │   │   ├── buffer
│   │   │   │   │   ├── enable
│   │   │   │   │   ├── length
│   │   │   │   │   └── watermark
│   │   │   │   ├── dev
│   │   │   │   ├── in_intensity_both_raw
│   │   │   │   ├── in_intensity_hysteresis
│   │   │   │   ├── in_intensity_offset
│   │   │   │   ├── in_intensity_sampling_frequency
│   │   │   │   ├── in_intensity_scale
│   │   │   │   ├── name
│   │   │   │   ├── scan_elements
│   │   │   │   │   ├── in_intensity_both_en
│   │   │   │   │   ├── in_intensity_both_index
│   │   │   │   │   └── in_intensity_both_type
│   │   │   │   ├── trigger
│   │   │   │   │   └── current_trigger
...
│   │   │   │   ├── buffer
│   │   │   │   │   ├── enable
│   │   │   │   │   ├── length
│   │   │   │   │   └── watermark
│   │   │   │   ├── dev
│   │   │   │   ├── in_magn_hysteresis
│   │   │   │   ├── in_magn_offset
│   │   │   │   ├── in_magn_sampling_frequency
│   │   │   │   ├── in_magn_scale
│   │   │   │   ├── in_magn_x_raw
│   │   │   │   ├── in_magn_y_raw
│   │   │   │   ├── in_magn_z_raw
│   │   │   │   ├── in_rot_from_north_magnetic_tilt_comp_raw
│   │   │   │   ├── in_rot_hysteresis
│   │   │   │   ├── in_rot_offset
│   │   │   │   ├── in_rot_sampling_frequency
│   │   │   │   ├── in_rot_scale
│   │   │   │   ├── name
...
│   │   │   │   ├── scan_elements
│   │   │   │   │   ├── in_magn_x_en
│   │   │   │   │   ├── in_magn_x_index
│   │   │   │   │   ├── in_magn_x_type
│   │   │   │   │   ├── in_magn_y_en
│   │   │   │   │   ├── in_magn_y_index
│   │   │   │   │   ├── in_magn_y_type
│   │   │   │   │   ├── in_magn_z_en
│   │   │   │   │   ├── in_magn_z_index
│   │   │   │   │   ├── in_magn_z_type
│   │   │   │   │   ├── in_rot_from_north_magnetic_tilt_comp_en
│   │   │   │   │   ├── in_rot_from_north_magnetic_tilt_comp_index
│   │   │   │   │   └── in_rot_from_north_magnetic_tilt_comp_type
│   │   │   │   ├── trigger
│   │   │   │   │   └── current_trigger
...
│   │   │   │   ├── buffer
│   │   │   │   │   ├── enable
│   │   │   │   │   ├── length
│   │   │   │   │   └── watermark
│   │   │   │   ├── dev
│   │   │   │   ├── in_anglvel_hysteresis
│   │   │   │   ├── in_anglvel_offset
│   │   │   │   ├── in_anglvel_sampling_frequency
│   │   │   │   ├── in_anglvel_scale
│   │   │   │   ├── in_anglvel_x_raw
│   │   │   │   ├── in_anglvel_y_raw
│   │   │   │   ├── in_anglvel_z_raw
│   │   │   │   ├── name
│   │   │   │   ├── scan_elements
│   │   │   │   │   ├── in_anglvel_x_en
│   │   │   │   │   ├── in_anglvel_x_index
│   │   │   │   │   ├── in_anglvel_x_type
│   │   │   │   │   ├── in_anglvel_y_en
│   │   │   │   │   ├── in_anglvel_y_index
│   │   │   │   │   ├── in_anglvel_y_type
│   │   │   │   │   ├── in_anglvel_z_en
│   │   │   │   │   ├── in_anglvel_z_index
│   │   │   │   │   └── in_anglvel_z_type
│   │   │   │   ├── trigger
│   │   │   │   │   └── current_trigger
...
│   │   │   │   ├── buffer
│   │   │   │   │   ├── enable
│   │   │   │   │   ├── length
│   │   │   │   │   └── watermark
│   │   │   │   ├── dev
│   │   │   │   ├── in_anglvel_hysteresis
│   │   │   │   ├── in_anglvel_offset
│   │   │   │   ├── in_anglvel_sampling_frequency
│   │   │   │   ├── in_anglvel_scale
│   │   │   │   ├── in_anglvel_x_raw
│   │   │   │   ├── in_anglvel_y_raw
│   │   │   │   ├── in_anglvel_z_raw
│   │   │   │   ├── name
│   │   │   │   ├── scan_elements
│   │   │   │   │   ├── in_anglvel_x_en
│   │   │   │   │   ├── in_anglvel_x_index
│   │   │   │   │   ├── in_anglvel_x_type
│   │   │   │   │   ├── in_anglvel_y_en
│   │   │   │   │   ├── in_anglvel_y_index
│   │   │   │   │   ├── in_anglvel_y_type
│   │   │   │   │   ├── in_anglvel_z_en
│   │   │   │   │   ├── in_anglvel_z_index
│   │   │   │   │   └── in_anglvel_z_type
│   │   │   │   ├── trigger
│   │   │   │   │   └── current_trigger
...

46
Documentation/hid/uhid.txt → Documentation/hid/uhid.rst
Просмотреть файл

@ -1,5 +1,6 @@
UHID - User-space I/O driver support for HID subsystem
========================================================
======================================================
UHID - User-space I/O driver support for HID subsystem
======================================================
UHID allows user-space to implement HID transport drivers. Please see
hid-transport.txt for an introduction into HID transport drivers. This document
@ -22,9 +23,9 @@ If a new device is detected by your HID I/O Driver and you want to register this
device with the HID subsystem, then you need to open /dev/uhid once for each
device you want to register. All further communication is done by read()'ing or
write()'ing "struct uhid_event" objects. Non-blocking operations are supported
by setting O_NONBLOCK.
by setting O_NONBLOCK::
struct uhid_event {
struct uhid_event {
__u32 type;
union {
struct uhid_create2_req create2;
@ -32,7 +33,7 @@ struct uhid_event {
struct uhid_input2_req input2;
...
} u;
};
};
The "type" field contains the ID of the event. Depending on the ID different
payloads are sent. You must not split a single event across multiple read()'s or
@ -86,31 +87,31 @@ the request was handled successfully. O_NONBLOCK does not affect write() as
writes are always handled immediately in a non-blocking fashion. Future requests
might make use of O_NONBLOCK, though.
UHID_CREATE2:
UHID_CREATE2:
This creates the internal HID device. No I/O is possible until you send this
event to the kernel. The payload is of type struct uhid_create2_req and
contains information about your device. You can start I/O now.
UHID_DESTROY:
UHID_DESTROY:
This destroys the internal HID device. No further I/O will be accepted. There
may still be pending messages that you can receive with read() but no further
UHID_INPUT events can be sent to the kernel.
You can create a new device by sending UHID_CREATE2 again. There is no need to
reopen the character device.
UHID_INPUT2:
UHID_INPUT2:
You must send UHID_CREATE2 before sending input to the kernel! This event
contains a data-payload. This is the raw data that you read from your device
on the interrupt channel. The kernel will parse the HID reports.
UHID_GET_REPORT_REPLY:
UHID_GET_REPORT_REPLY:
If you receive a UHID_GET_REPORT request you must answer with this request.
You must copy the "id" field from the request into the answer. Set the "err"
field to 0 if no error occurred or to EIO if an I/O error occurred.
If "err" is 0 then you should fill the buffer of the answer with the results
of the GET_REPORT request and set "size" correspondingly.
UHID_SET_REPORT_REPLY:
UHID_SET_REPORT_REPLY:
This is the SET_REPORT equivalent of UHID_GET_REPORT_REPLY. Unlike GET_REPORT,
SET_REPORT never returns a data buffer, therefore, it's sufficient to set the
"id" and "err" fields correctly.
@ -120,16 +121,18 @@ read()
read() will return a queued output report. No reaction is required to any of
them but you should handle them according to your needs.
UHID_START:
UHID_START:
This is sent when the HID device is started. Consider this as an answer to
UHID_CREATE2. This is always the first event that is sent. Note that this
event might not be available immediately after write(UHID_CREATE2) returns.
Device drivers might required delayed setups.
This event contains a payload of type uhid_start_req. The "dev_flags" field
describes special behaviors of a device. The following flags are defined:
UHID_DEV_NUMBERED_FEATURE_REPORTS:
UHID_DEV_NUMBERED_OUTPUT_REPORTS:
UHID_DEV_NUMBERED_INPUT_REPORTS:
- UHID_DEV_NUMBERED_FEATURE_REPORTS
- UHID_DEV_NUMBERED_OUTPUT_REPORTS
- UHID_DEV_NUMBERED_INPUT_REPORTS
Each of these flags defines whether a given report-type uses numbered
reports. If numbered reports are used for a type, all messages from
the kernel already have the report-number as prefix. Otherwise, no
@ -137,33 +140,35 @@ them but you should handle them according to your needs.
For messages sent by user-space to the kernel, you must adjust the
prefixes according to these flags.
UHID_STOP:
UHID_STOP:
This is sent when the HID device is stopped. Consider this as an answer to
UHID_DESTROY.
If you didn't destroy your device via UHID_DESTROY, but the kernel sends an
UHID_STOP event, this should usually be ignored. It means that the kernel
reloaded/changed the device driver loaded on your HID device (or some other
maintenance actions happened).
You can usually ignored any UHID_STOP events safely.
UHID_OPEN:
UHID_OPEN:
This is sent when the HID device is opened. That is, the data that the HID
device provides is read by some other process. You may ignore this event but
it is useful for power-management. As long as you haven't received this event
there is actually no other process that reads your data so there is no need to
send UHID_INPUT2 events to the kernel.
UHID_CLOSE:
UHID_CLOSE:
This is sent when there are no more processes which read the HID data. It is
the counterpart of UHID_OPEN and you may as well ignore this event.
UHID_OUTPUT:
UHID_OUTPUT:
This is sent if the HID device driver wants to send raw data to the I/O
device on the interrupt channel. You should read the payload and forward it to
the device. The payload is of type "struct uhid_output_req".
This may be received even though you haven't received UHID_OPEN, yet.
UHID_GET_REPORT:
UHID_GET_REPORT:
This event is sent if the kernel driver wants to perform a GET_REPORT request
on the control channeld as described in the HID specs. The report-type and
report-number are available in the payload.
@ -177,11 +182,12 @@ them but you should handle them according to your needs.
timed out, the kernel will ignore the response silently. The "id" field is
never re-used, so conflicts cannot happen.
UHID_SET_REPORT:
UHID_SET_REPORT:
This is the SET_REPORT equivalent of UHID_GET_REPORT. On receipt, you shall
send a SET_REPORT request to your hid device. Once it replies, you must tell
the kernel about it via UHID_SET_REPORT_REPLY.
The same restrictions as for UHID_GET_REPORT apply.
----------------------------------------------------
Written 2012, David Herrmann <dh.herrmann@gmail.com>

2
Documentation/input/input.rst
Просмотреть файл

@ -188,7 +188,7 @@ LCDs and many other purposes.
The monitor and speaker controls should be easy to add to the hid/input
interface, but for the UPSs and LCDs it doesn't make much sense. For this,
the hiddev interface was designed. See Documentation/hid/hiddev.txt
the hiddev interface was designed. See Documentation/hid/hiddev.rst
for more information about it.
The usage of the usbhid module is very simple, it takes no parameters,

2
MAINTAINERS
Просмотреть файл

@ -16319,7 +16319,7 @@ M: Benjamin Tissoires <benjamin.tissoires@redhat.com>
L: linux-usb@vger.kernel.org
T: git git://git.kernel.org/pub/scm/linux/kernel/git/hid/hid.git
S: Maintained
F: Documentation/hid/hiddev.txt
F: Documentation/hid/hiddev.rst
F: drivers/hid/usbhid/
USB INTEL XHCI ROLE MUX DRIVER