gpiolib: pcf857x i2c gpio expander support
This is a new-style I2C driver for most common 8 and 16 bit I2C based "quasi-bidirectional" GPIO expanders: pcf8574 or pcf8575, and several compatible models (mostly faster, supporting I2C at up to 1 MHz). The driver exposes the GPIO signals using the platform-neutral GPIO programming interface, so they are easily accessed by other kernel code. The lack of such a flexible kernel API has been a big factor in the proliferation of board-specific drivers for these chips... stuff that rarely makes it upstream since it's so ugly. This driver will let such boards use standard calls. Since it's a new-style driver, these devices must be configured as part of board-specific init. That eliminates the need for error-prone manual configuration of module parameters, and makes compatibility with legacy drivers (pcf8574.c, pc8575.c) for these chips easier (there's a clear either/or disjunction). Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Acked-by: Jean Delvare <khali@linux-fr.org> Cc: Eric Miao <eric.miao@marvell.com> Cc: Sam Ravnborg <sam@ravnborg.org> Cc: Haavard Skinnemoen <hskinnemoen@atmel.com> Cc: Philipp Zabel <philipp.zabel@gmail.com> Cc: Russell King <rmk@arm.linux.org.uk> Cc: Ben Gardner <bgardner@wabtec.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David Brownell
Linus Torvalds
Родитель
1c44f5f16f
Коммит
15fae37d9f
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@ -27,6 +27,29 @@ config DEBUG_GPIO
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comment "I2C GPIO expanders:"
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config GPIO_PCF857X
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tristate "PCF857x, PCA857x, and PCA967x I2C GPIO expanders"
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depends on I2C
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help
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Say yes here to provide access to most "quasi-bidirectional" I2C
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GPIO expanders used for additional digital outputs or inputs.
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Most of these parts are from NXP, though TI is a second source for
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some of them. Compatible models include:
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8 bits: pcf8574, pcf8574a, pca8574, pca8574a,
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pca9670, pca9672, pca9674, pca9674a
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16 bits: pcf8575, pcf8575c, pca8575,
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pca9671, pca9673, pca9675
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Your board setup code will need to declare the expanders in
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use, and assign numbers to the GPIOs they expose. Those GPIOs
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can then be used from drivers and other kernel code, just like
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other GPIOs, but only accessible from task contexts.
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This driver provides an in-kernel interface to those GPIOs using
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platform-neutral GPIO calls.
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comment "SPI GPIO expanders:"
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endmenu
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@ -4,3 +4,4 @@ ccflags-$(CONFIG_DEBUG_GPIO) += -DDEBUG
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obj-$(CONFIG_HAVE_GPIO_LIB) += gpiolib.o
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obj-$(CONFIG_GPIO_PCF857X) += pcf857x.o
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@ -0,0 +1,330 @@
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/*
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* pcf857x - driver for pcf857x, pca857x, and pca967x I2C GPIO expanders
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*
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* Copyright (C) 2007 David Brownell
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include <linux/kernel.h>
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#include <linux/slab.h>
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#include <linux/i2c.h>
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#include <linux/i2c/pcf857x.h>
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#include <asm/gpio.h>
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/*
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* The pcf857x, pca857x, and pca967x chips only expose one read and one
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* write register. Writing a "one" bit (to match the reset state) lets
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* that pin be used as an input; it's not an open-drain model, but acts
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* a bit like one. This is described as "quasi-bidirectional"; read the
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* chip documentation for details.
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*
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* Many other I2C GPIO expander chips (like the pca953x models) have
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* more complex register models and more conventional circuitry using
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* push/pull drivers. They often use the same 0x20..0x27 addresses as
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* pcf857x parts, making the "legacy" I2C driver model problematic.
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*/
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struct pcf857x {
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struct gpio_chip chip;
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struct i2c_client *client;
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unsigned out; /* software latch */
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};
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/*-------------------------------------------------------------------------*/
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/* Talk to 8-bit I/O expander */
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static int pcf857x_input8(struct gpio_chip *chip, unsigned offset)
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{
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struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
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gpio->out |= (1 << offset);
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return i2c_smbus_write_byte(gpio->client, gpio->out);
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}
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static int pcf857x_get8(struct gpio_chip *chip, unsigned offset)
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{
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struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
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s32 value;
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value = i2c_smbus_read_byte(gpio->client);
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return (value < 0) ? 0 : (value & (1 << offset));
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}
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static int pcf857x_output8(struct gpio_chip *chip, unsigned offset, int value)
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{
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struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
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unsigned bit = 1 << offset;
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if (value)
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gpio->out |= bit;
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else
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gpio->out &= ~bit;
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return i2c_smbus_write_byte(gpio->client, gpio->out);
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}
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static void pcf857x_set8(struct gpio_chip *chip, unsigned offset, int value)
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{
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pcf857x_output8(chip, offset, value);
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}
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/*-------------------------------------------------------------------------*/
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/* Talk to 16-bit I/O expander */
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static int i2c_write_le16(struct i2c_client *client, u16 word)
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{
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u8 buf[2] = { word & 0xff, word >> 8, };
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int status;
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status = i2c_master_send(client, buf, 2);
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return (status < 0) ? status : 0;
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}
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static int i2c_read_le16(struct i2c_client *client)
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{
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u8 buf[2];
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int status;
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status = i2c_master_recv(client, buf, 2);
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if (status < 0)
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return status;
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return (buf[1] << 8) | buf[0];
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}
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static int pcf857x_input16(struct gpio_chip *chip, unsigned offset)
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{
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struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
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gpio->out |= (1 << offset);
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return i2c_write_le16(gpio->client, gpio->out);
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}
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static int pcf857x_get16(struct gpio_chip *chip, unsigned offset)
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{
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struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
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int value;
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value = i2c_read_le16(gpio->client);
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return (value < 0) ? 0 : (value & (1 << offset));
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}
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static int pcf857x_output16(struct gpio_chip *chip, unsigned offset, int value)
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{
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struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
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unsigned bit = 1 << offset;
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if (value)
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gpio->out |= bit;
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else
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gpio->out &= ~bit;
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return i2c_write_le16(gpio->client, gpio->out);
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}
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static void pcf857x_set16(struct gpio_chip *chip, unsigned offset, int value)
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{
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pcf857x_output16(chip, offset, value);
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}
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/*-------------------------------------------------------------------------*/
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static int pcf857x_probe(struct i2c_client *client)
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{
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struct pcf857x_platform_data *pdata;
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struct pcf857x *gpio;
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int status;
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pdata = client->dev.platform_data;
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if (!pdata)
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return -ENODEV;
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/* Allocate, initialize, and register this gpio_chip. */
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gpio = kzalloc(sizeof *gpio, GFP_KERNEL);
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if (!gpio)
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return -ENOMEM;
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gpio->chip.base = pdata->gpio_base;
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gpio->chip.can_sleep = 1;
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/* NOTE: the OnSemi jlc1562b is also largely compatible with
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* these parts, notably for output. It has a low-resolution
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* DAC instead of pin change IRQs; and its inputs can be the
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* result of comparators.
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*/
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/* 8574 addresses are 0x20..0x27; 8574a uses 0x38..0x3f;
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* 9670, 9672, 9764, and 9764a use quite a variety.
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*
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* NOTE: we don't distinguish here between *4 and *4a parts.
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*/
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if (strcmp(client->name, "pcf8574") == 0
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|| strcmp(client->name, "pca8574") == 0
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|| strcmp(client->name, "pca9670") == 0
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|| strcmp(client->name, "pca9672") == 0
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|| strcmp(client->name, "pca9674") == 0
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) {
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gpio->chip.ngpio = 8;
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gpio->chip.direction_input = pcf857x_input8;
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gpio->chip.get = pcf857x_get8;
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gpio->chip.direction_output = pcf857x_output8;
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gpio->chip.set = pcf857x_set8;
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if (!i2c_check_functionality(client->adapter,
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I2C_FUNC_SMBUS_BYTE))
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status = -EIO;
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/* fail if there's no chip present */
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else
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status = i2c_smbus_read_byte(client);
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/* '75/'75c addresses are 0x20..0x27, just like the '74;
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* the '75c doesn't have a current source pulling high.
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* 9671, 9673, and 9765 use quite a variety of addresses.
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*
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* NOTE: we don't distinguish here between '75 and '75c parts.
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*/
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} else if (strcmp(client->name, "pcf8575") == 0
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|| strcmp(client->name, "pca8575") == 0
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|| strcmp(client->name, "pca9671") == 0
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|| strcmp(client->name, "pca9673") == 0
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|| strcmp(client->name, "pca9675") == 0
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) {
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gpio->chip.ngpio = 16;
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gpio->chip.direction_input = pcf857x_input16;
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gpio->chip.get = pcf857x_get16;
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gpio->chip.direction_output = pcf857x_output16;
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gpio->chip.set = pcf857x_set16;
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if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
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status = -EIO;
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/* fail if there's no chip present */
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else
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status = i2c_read_le16(client);
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} else
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status = -ENODEV;
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if (status < 0)
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goto fail;
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gpio->chip.label = client->name;
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gpio->client = client;
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i2c_set_clientdata(client, gpio);
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/* NOTE: these chips have strange "quasi-bidirectional" I/O pins.
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* We can't actually know whether a pin is configured (a) as output
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* and driving the signal low, or (b) as input and reporting a low
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* value ... without knowing the last value written since the chip
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* came out of reset (if any). We can't read the latched output.
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*
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* In short, the only reliable solution for setting up pin direction
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* is to do it explicitly. The setup() method can do that, but it
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* may cause transient glitching since it can't know the last value
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* written (some pins may need to be driven low).
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*
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* Using pdata->n_latch avoids that trouble. When left initialized
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* to zero, our software copy of the "latch" then matches the chip's
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* all-ones reset state. Otherwise it flags pins to be driven low.
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*/
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gpio->out = ~pdata->n_latch;
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status = gpiochip_add(&gpio->chip);
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if (status < 0)
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goto fail;
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/* NOTE: these chips can issue "some pin-changed" IRQs, which we
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* don't yet even try to use. Among other issues, the relevant
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* genirq state isn't available to modular drivers; and most irq
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* methods can't be called from sleeping contexts.
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*/
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dev_info(&client->dev, "gpios %d..%d on a %s%s\n",
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gpio->chip.base,
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gpio->chip.base + gpio->chip.ngpio - 1,
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client->name,
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client->irq ? " (irq ignored)" : "");
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/* Let platform code set up the GPIOs and their users.
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* Now is the first time anyone could use them.
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*/
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if (pdata->setup) {
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status = pdata->setup(client,
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gpio->chip.base, gpio->chip.ngpio,
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pdata->context);
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if (status < 0)
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dev_warn(&client->dev, "setup --> %d\n", status);
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}
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return 0;
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fail:
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dev_dbg(&client->dev, "probe error %d for '%s'\n",
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status, client->name);
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kfree(gpio);
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return status;
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}
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static int pcf857x_remove(struct i2c_client *client)
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{
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struct pcf857x_platform_data *pdata = client->dev.platform_data;
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struct pcf857x *gpio = i2c_get_clientdata(client);
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int status = 0;
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if (pdata->teardown) {
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status = pdata->teardown(client,
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gpio->chip.base, gpio->chip.ngpio,
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pdata->context);
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if (status < 0) {
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dev_err(&client->dev, "%s --> %d\n",
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"teardown", status);
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return status;
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}
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}
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status = gpiochip_remove(&gpio->chip);
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if (status == 0)
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kfree(gpio);
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else
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dev_err(&client->dev, "%s --> %d\n", "remove", status);
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return status;
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}
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static struct i2c_driver pcf857x_driver = {
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.driver = {
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.name = "pcf857x",
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.owner = THIS_MODULE,
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},
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.probe = pcf857x_probe,
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.remove = pcf857x_remove,
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};
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static int __init pcf857x_init(void)
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{
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return i2c_add_driver(&pcf857x_driver);
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}
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module_init(pcf857x_init);
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static void __exit pcf857x_exit(void)
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{
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i2c_del_driver(&pcf857x_driver);
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}
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module_exit(pcf857x_exit);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("David Brownell");
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@ -0,0 +1,45 @@
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#ifndef __LINUX_PCF857X_H
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#define __LINUX_PCF857X_H
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/**
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* struct pcf857x_platform_data - data to set up pcf857x driver
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* @gpio_base: number of the chip's first GPIO
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* @n_latch: optional bit-inverse of initial register value; if
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* you leave this initialized to zero the driver will act
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* like the chip was just reset
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* @setup: optional callback issued once the GPIOs are valid
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* @teardown: optional callback issued before the GPIOs are invalidated
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* @context: optional parameter passed to setup() and teardown()
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*
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* In addition to the I2C_BOARD_INFO() state appropriate to each chip,
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* the i2c_board_info used with the pcf875x driver must provide the
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* chip "type" ("pcf8574", "pcf8574a", "pcf8575", "pcf8575c") and its
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* platform_data (pointer to one of these structures) with at least
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* the gpio_base value initialized.
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*
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* The @setup callback may be used with the kind of board-specific glue
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* which hands the (now-valid) GPIOs to other drivers, or which puts
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* devices in their initial states using these GPIOs.
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*
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* These GPIO chips are only "quasi-bidirectional"; read the chip specs
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* to understand the behavior. They don't have separate registers to
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* record which pins are used for input or output, record which output
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* values are driven, or provide access to input values. That must be
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* inferred by reading the chip's value and knowing the last value written
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* to it. If you leave n_latch initialized to zero, that last written
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* value is presumed to be all ones (as if the chip were just reset).
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*/
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struct pcf857x_platform_data {
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unsigned gpio_base;
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unsigned n_latch;
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int (*setup)(struct i2c_client *client,
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int gpio, unsigned ngpio,
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void *context);
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int (*teardown)(struct i2c_client *client,
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int gpio, unsigned ngpio,
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void *context);
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void *context;
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};
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#endif /* __LINUX_PCF857X_H */
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