regmap: Add generic non-memory mapped register access API

There are many places in the tree where we implement register access for
devices on non-memory mapped buses, especially I2C and SPI. Since hardware
designers seem to have settled on a relatively consistent set of register
interfaces this can be effectively factored out into shared code.  There
are a standard set of formats for marshalling data for exchange with the
device, with the actual I/O mechanisms generally being simple byte
streams.

We create an abstraction for marshaling data into formats which can be
sent on the control interfaces, and create a standard method for
plugging in actual transport underneath that.

This is mostly a refactoring and renaming of the bottom level of the
existing code for sharing register I/O which we have in ASoC. A
subsequent patch in this series converts ASoC to use this.  The main
difference in interface is that reads return values by writing to a
location provided by a pointer rather than in the return value, ensuring
we can use the full range of the type for register data.  We also use
unsigned types rather than ints for the same reason.

As some of the devices can have very large register maps the existing
ASoC code also contains infrastructure for managing register caches.
This cache work will be moved over in a future stage to allow for
separate review, the current patch only deals with the physical I/O.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Liam Girdwood <lrg@ti.com>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Acked-by: Wolfram Sang <w.sang@pengutronix.de>
Acked-by: Grant Likely <grant.likely@secretlab.ca>

MAINTAINERS

@@ -5313,6 +5313,13 @@ L:	reiserfs-devel@vger.kernel.org
 S:	Supported
 F:	fs/reiserfs/
 
+REGISTER MAP ABSTRACTION
+M:	Mark Brown <broonie@opensource.wolfsonmicro.com>
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/broonie/regmap.git
+S:	Supported
+F:	drivers/base/regmap/
+F:	include/linux/regmap.h
+
 RFKILL
 M:	Johannes Berg <johannes@sipsolutions.net>
 L:	linux-wireless@vger.kernel.org

drivers/base/Kconfig

@@ -168,4 +168,6 @@ config SYS_HYPERVISOR
 	bool
 	default n
 
+source "drivers/base/regmap/Kconfig"
+
 endmenu

drivers/base/Makefile

@@ -18,6 +18,7 @@ ifeq ($(CONFIG_SYSFS),y)
 obj-$(CONFIG_MODULES)	+= module.o
 endif
 obj-$(CONFIG_SYS_HYPERVISOR) += hypervisor.o
+obj-$(CONFIG_REGMAP)	+= regmap/
 
 ccflags-$(CONFIG_DEBUG_DRIVER) := -DDEBUG
 

drivers/base/regmap/Kconfig

@@ -0,0 +1,6 @@
+# Generic register map support.  There are no user servicable options here,
+# this is an API intended to be used by other kernel subsystems.  These
+# subsystems should select the appropriate symbols.
+
+config REGMAP
+	bool

drivers/base/regmap/Makefile

@@ -0,0 +1 @@
+obj-$(CONFIG_REGMAP) += regmap.o

drivers/base/regmap/regmap.c

@@ -0,0 +1,455 @@
+/*
+ * Register map access API
+ *
+ * Copyright 2011 Wolfson Microelectronics plc
+ *
+ * Author: Mark Brown <broonie@opensource.wolfsonmicro.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/err.h>
+
+#include <linux/regmap.h>
+
+struct regmap;
+
+struct regmap_format {
+	size_t buf_size;
+	size_t reg_bytes;
+	size_t val_bytes;
+	void (*format_write)(struct regmap *map,
+			     unsigned int reg, unsigned int val);
+	void (*format_reg)(void *buf, unsigned int reg);
+	void (*format_val)(void *buf, unsigned int val);
+	unsigned int (*parse_val)(void *buf);
+};
+
+struct regmap {
+	struct mutex lock;
+
+	struct device *dev; /* Device we do I/O on */
+	void *work_buf;     /* Scratch buffer used to format I/O */
+	struct regmap_format format;  /* Buffer format */
+	const struct regmap_bus *bus;
+};
+
+static void regmap_format_4_12_write(struct regmap *map,
+				     unsigned int reg, unsigned int val)
+{
+	__be16 *out = map->work_buf;
+	*out = cpu_to_be16((reg << 12) | val);
+}
+
+static void regmap_format_7_9_write(struct regmap *map,
+				    unsigned int reg, unsigned int val)
+{
+	__be16 *out = map->work_buf;
+	*out = cpu_to_be16((reg << 9) | val);
+}
+
+static void regmap_format_8(void *buf, unsigned int val)
+{
+	u8 *b = buf;
+
+	b[0] = val;
+}
+
+static void regmap_format_16(void *buf, unsigned int val)
+{
+	__be16 *b = buf;
+
+	b[0] = cpu_to_be16(val);
+}
+
+static unsigned int regmap_parse_8(void *buf)
+{
+	u8 *b = buf;
+
+	return b[0];
+}
+
+static unsigned int regmap_parse_16(void *buf)
+{
+	__be16 *b = buf;
+
+	b[0] = be16_to_cpu(b[0]);
+
+	return b[0];
+}
+
+/**
+ * regmap_init(): Initialise register map
+ *
+ * @dev: Device that will be interacted with
+ * @bus: Bus-specific callbacks to use with device
+ * @config: Configuration for register map
+ *
+ * The return value will be an ERR_PTR() on error or a valid pointer to
+ * a struct regmap.  This function should generally not be called
+ * directly, it should be called by bus-specific init functions.
+ */
+struct regmap *regmap_init(struct device *dev,
+			   const struct regmap_bus *bus,
+			   const struct regmap_config *config)
+{
+	struct regmap *map;
+	int ret = -EINVAL;
+
+	if (!bus || !config)
+		return NULL;
+
+	map = kzalloc(sizeof(*map), GFP_KERNEL);
+	if (map == NULL) {
+		ret = -ENOMEM;
+		goto err;
+	}
+
+	mutex_init(&map->lock);
+	map->format.buf_size = (config->reg_bits + config->val_bits) / 8;
+	map->format.reg_bytes = config->reg_bits / 8;
+	map->format.val_bytes = config->val_bits / 8;
+	map->dev = dev;
+	map->bus = bus;
+
+	switch (config->reg_bits) {
+	case 4:
+		switch (config->val_bits) {
+		case 12:
+			map->format.format_write = regmap_format_4_12_write;
+			break;
+		default:
+			goto err_map;
+		}
+		break;
+
+	case 7:
+		switch (config->val_bits) {
+		case 9:
+			map->format.format_write = regmap_format_7_9_write;
+			break;
+		default:
+			goto err_map;
+		}
+		break;
+
+	case 8:
+		map->format.format_reg = regmap_format_8;
+		break;
+
+	case 16:
+		map->format.format_reg = regmap_format_16;
+		break;
+
+	default:
+		goto err_map;
+	}
+
+	switch (config->val_bits) {
+	case 8:
+		map->format.format_val = regmap_format_8;
+		map->format.parse_val = regmap_parse_8;
+		break;
+	case 16:
+		map->format.format_val = regmap_format_16;
+		map->format.parse_val = regmap_parse_16;
+		break;
+	}
+
+	if (!map->format.format_write &&
+	    !(map->format.format_reg && map->format.format_val))
+		goto err_map;
+
+	map->work_buf = kmalloc(map->format.buf_size, GFP_KERNEL);
+	if (map->work_buf == NULL) {
+		ret = -ENOMEM;
+		goto err_bus;
+	}
+
+	return map;
+
+err_bus:
+	module_put(map->bus->owner);
+err_map:
+	kfree(map);
+err:
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(regmap_init);
+
+/**
+ * regmap_exit(): Free a previously allocated register map
+ */
+void regmap_exit(struct regmap *map)
+{
+	kfree(map->work_buf);
+	module_put(map->bus->owner);
+	kfree(map);
+}
+EXPORT_SYMBOL_GPL(regmap_exit);
+
+static int _regmap_raw_write(struct regmap *map, unsigned int reg,
+			     const void *val, size_t val_len)
+{
+	void *buf;
+	int ret = -ENOTSUPP;
+	size_t len;
+
+	map->format.format_reg(map->work_buf, reg);
+
+	/* Try to do a gather write if we can */
+	if (map->bus->gather_write)
+		ret = map->bus->gather_write(map->dev, map->work_buf,
+					     map->format.reg_bytes,
+					     val, val_len);
+
+	/* Otherwise fall back on linearising by hand. */
+	if (ret == -ENOTSUPP) {
+		len = map->format.reg_bytes + val_len;
+		buf = kmalloc(len, GFP_KERNEL);
+		if (!buf)
+			return -ENOMEM;
+
+		memcpy(buf, map->work_buf, map->format.reg_bytes);
+		memcpy(buf + map->format.reg_bytes, val, val_len);
+		ret = map->bus->write(map->dev, buf, len);
+
+		kfree(buf);
+	}
+
+	return ret;
+}
+
+static int _regmap_write(struct regmap *map, unsigned int reg,
+			 unsigned int val)
+{
+	BUG_ON(!map->format.format_write && !map->format.format_val);
+
+	if (map->format.format_write) {
+		map->format.format_write(map, reg, val);
+
+		return map->bus->write(map->dev, map->work_buf,
+				       map->format.buf_size);
+	} else {
+		map->format.format_val(map->work_buf + map->format.reg_bytes,
+				       val);
+		return _regmap_raw_write(map, reg,
+					 map->work_buf + map->format.reg_bytes,
+					 map->format.val_bytes);
+	}
+}
+
+/**
+ * regmap_write(): Write a value to a single register
+ *
+ * @map: Register map to write to
+ * @reg: Register to write to
+ * @val: Value to be written
+ *
+ * A value of zero will be returned on success, a negative errno will
+ * be returned in error cases.
+ */
+int regmap_write(struct regmap *map, unsigned int reg, unsigned int val)
+{
+	int ret;
+
+	mutex_lock(&map->lock);
+
+	ret = _regmap_write(map, reg, val);
+
+	mutex_unlock(&map->lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(regmap_write);
+
+/**
+ * regmap_raw_write(): Write raw values to one or more registers
+ *
+ * @map: Register map to write to
+ * @reg: Initial register to write to
+ * @val: Block of data to be written, laid out for direct transmission to the
+ *       device
+ * @val_len: Length of data pointed to by val.
+ *
+ * This function is intended to be used for things like firmware
+ * download where a large block of data needs to be transferred to the
+ * device.  No formatting will be done on the data provided.
+ *
+ * A value of zero will be returned on success, a negative errno will
+ * be returned in error cases.
+ */
+int regmap_raw_write(struct regmap *map, unsigned int reg,
+		     const void *val, size_t val_len)
+{
+	int ret;
+
+	mutex_lock(&map->lock);
+
+	ret = _regmap_raw_write(map, reg, val, val_len);
+
+	mutex_unlock(&map->lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(regmap_raw_write);
+
+static int _regmap_raw_read(struct regmap *map, unsigned int reg, void *val,
+			    unsigned int val_len)
+{
+	u8 *u8 = map->work_buf;
+	int ret;
+
+	map->format.format_reg(map->work_buf, reg);
+
+	/*
+	 * Some buses flag reads by setting the high bits in the
+	 * register addresss; since it's always the high bits for all
+	 * current formats we can do this here rather than in
+	 * formatting.  This may break if we get interesting formats.
+	 */
+	if (map->bus->read_flag_mask)
+		u8[0] |= map->bus->read_flag_mask;
+
+	ret = map->bus->read(map->dev, map->work_buf, map->format.reg_bytes,
+			     val, map->format.val_bytes);
+	if (ret != 0)
+		return ret;
+
+	return 0;
+}
+
+static int _regmap_read(struct regmap *map, unsigned int reg,
+			unsigned int *val)
+{
+	int ret;
+
+	if (!map->format.parse_val)
+		return -EINVAL;
+
+	ret = _regmap_raw_read(map, reg, map->work_buf, map->format.val_bytes);
+	if (ret == 0)
+		*val = map->format.parse_val(map->work_buf);
+
+	return ret;
+}
+
+/**
+ * regmap_read(): Read a value from a single register
+ *
+ * @map: Register map to write to
+ * @reg: Register to be read from
+ * @val: Pointer to store read value
+ *
+ * A value of zero will be returned on success, a negative errno will
+ * be returned in error cases.
+ */
+int regmap_read(struct regmap *map, unsigned int reg, unsigned int *val)
+{
+	int ret;
+
+	mutex_lock(&map->lock);
+
+	ret = _regmap_read(map, reg, val);
+
+	mutex_unlock(&map->lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(regmap_read);
+
+/**
+ * regmap_raw_read(): Read raw data from the device
+ *
+ * @map: Register map to write to
+ * @reg: First register to be read from
+ * @val: Pointer to store read value
+ * @val_len: Size of data to read
+ *
+ * A value of zero will be returned on success, a negative errno will
+ * be returned in error cases.
+ */
+int regmap_raw_read(struct regmap *map, unsigned int reg, void *val,
+		    size_t val_len)
+{
+	int ret;
+
+	mutex_lock(&map->lock);
+
+	ret = _regmap_raw_read(map, reg, val, val_len);
+
+	mutex_unlock(&map->lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(regmap_raw_read);
+
+/**
+ * regmap_bulk_read(): Read multiple registers from the device
+ *
+ * @map: Register map to write to
+ * @reg: First register to be read from
+ * @val: Pointer to store read value, in native register size for device
+ * @val_count: Number of registers to read
+ *
+ * A value of zero will be returned on success, a negative errno will
+ * be returned in error cases.
+ */
+int regmap_bulk_read(struct regmap *map, unsigned int reg, void *val,
+		     size_t val_count)
+{
+	int ret, i;
+	size_t val_bytes = map->format.val_bytes;
+
+	if (!map->format.parse_val)
+		return -EINVAL;
+
+	ret = regmap_raw_read(map, reg, val, val_bytes * val_count);
+	if (ret != 0)
+		return ret;
+
+	for (i = 0; i < val_count * val_bytes; i += val_bytes)
+		map->format.parse_val(val + i);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(regmap_bulk_read);
+
+/**
+ * remap_update_bits: Perform a read/modify/write cycle on the register map
+ *
+ * @map: Register map to update
+ * @reg: Register to update
+ * @mask: Bitmask to change
+ * @val: New value for bitmask
+ *
+ * Returns zero for success, a negative number on error.
+ */
+int regmap_update_bits(struct regmap *map, unsigned int reg,
+		       unsigned int mask, unsigned int val)
+{
+	int ret;
+	unsigned int tmp;
+
+	mutex_lock(&map->lock);
+
+	ret = _regmap_read(map, reg, &tmp);
+	if (ret != 0)
+		goto out;
+
+	tmp &= ~mask;
+	tmp |= val & mask;
+
+	ret = _regmap_write(map, reg, tmp);
+
+out:
+	mutex_unlock(&map->lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(regmap_update_bits);

include/linux/regmap.h

@@ -0,0 +1,74 @@
+#ifndef __LINUX_REGMAP_H
+#define __LINUX_REGMAP_H
+
+/*
+ * Register map access API
+ *
+ * Copyright 2011 Wolfson Microelectronics plc
+ *
+ * Author: Mark Brown <broonie@opensource.wolfsonmicro.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/device.h>
+#include <linux/list.h>
+#include <linux/module.h>
+
+struct regmap_config {
+	int reg_bits;
+	int val_bits;
+};
+
+typedef int (*regmap_hw_write)(struct device *dev, const void *data,
+			       size_t count);
+typedef int (*regmap_hw_gather_write)(struct device *dev,
+				      const void *reg, size_t reg_len,
+				      const void *val, size_t val_len);
+typedef int (*regmap_hw_read)(struct device *dev,
+			      const void *reg_buf, size_t reg_size,
+			      void *val_buf, size_t val_size);
+
+/**
+ * Description of a hardware bus for the register map infrastructure.
+ *
+ * @list: Internal use.
+ * @type: Bus type, used to identify bus to be used for a device.
+ * @write: Write operation.
+ * @gather_write: Write operation with split register/value, return -ENOTSUPP
+ *                if not implemented  on a given device.
+ * @read: Read operation.  Data is returned in the buffer used to transmit
+ *         data.
+ * @owner: Module with the bus implementation, used to pin the implementation
+ *         in memory.
+ * @read_flag_mask: Mask to be set in the top byte of the register when doing
+ *                  a read.
+ */
+struct regmap_bus {
+	struct list_head list;
+	struct bus_type *type;
+	regmap_hw_write write;
+	regmap_hw_gather_write gather_write;
+	regmap_hw_read read;
+	struct module *owner;
+	u8 read_flag_mask;
+};
+
+struct regmap *regmap_init(struct device *dev,
+			   const struct regmap_bus *bus,
+			   const struct regmap_config *config);
+void regmap_exit(struct regmap *map);
+int regmap_write(struct regmap *map, unsigned int reg, unsigned int val);
+int regmap_raw_write(struct regmap *map, unsigned int reg,
+		     const void *val, size_t val_len);
+int regmap_read(struct regmap *map, unsigned int reg, unsigned int *val);
+int regmap_raw_read(struct regmap *map, unsigned int reg,
+		    void *val, size_t val_len);
+int regmap_bulk_read(struct regmap *map, unsigned int reg, void *val,
+		     size_t val_count);
+int regmap_update_bits(struct regmap *map, unsigned int reg,
+		       unsigned int mask, unsigned int val);
+
+#endif