gpio: add driver for MAX7300 I2C GPIO extender

Add the MAX7300-I2C variant of the MAX7301-SPI version.  Both chips share
the same core logic, so the generic part of the in-kernel SPI-driver is
refactored into a generic part.  The I2C and SPI specific funtions are
then wrapped into seperate drivers picking up the generic part.

Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Cc: Juergen Beisert <j.beisert@pengutronix.de>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Cc: Jean Delvare <khali@linux-fr.org>
Cc: Anton Vorontsov <avorontsov@ru.mvista.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/gpio/Kconfig

@@ -65,6 +65,9 @@ config GPIO_SYSFS
 
 # put expanders in the right section, in alphabetical order
 
+config GPIO_MAX730X
+	tristate
+
 comment "Memory mapped GPIO expanders:"
 
 config GPIO_PL061
@@ -87,6 +90,13 @@ config GPIO_VR41XX
 
 comment "I2C GPIO expanders:"
 
+config GPIO_MAX7300
+	tristate "Maxim MAX7300 GPIO expander"
+	depends on I2C
+	select GPIO_MAX730X
+	help
+	  GPIO driver for Maxim MAX7301 I2C-based GPIO expander.
+
 config GPIO_MAX732X
 	tristate "MAX7319, MAX7320-7327 I2C Port Expanders"
 	depends on I2C
@@ -226,8 +236,9 @@ comment "SPI GPIO expanders:"
 config GPIO_MAX7301
 	tristate "Maxim MAX7301 GPIO expander"
 	depends on SPI_MASTER
+	select GPIO_MAX730X
 	help
-	  gpio driver for Maxim MAX7301 SPI GPIO expander.
+	  GPIO driver for Maxim MAX7301 SPI-based GPIO expander.
 
 config GPIO_MCP23S08
 	tristate "Microchip MCP23S08 I/O expander"

drivers/gpio/Makefile

@@ -7,6 +7,8 @@ obj-$(CONFIG_GPIOLIB)		+= gpiolib.o
 obj-$(CONFIG_GPIO_ADP5520)	+= adp5520-gpio.o
 obj-$(CONFIG_GPIO_ADP5588)	+= adp5588-gpio.o
 obj-$(CONFIG_GPIO_LANGWELL)	+= langwell_gpio.o
+obj-$(CONFIG_GPIO_MAX730X)	+= max730x.o
+obj-$(CONFIG_GPIO_MAX7300)	+= max7300.o
 obj-$(CONFIG_GPIO_MAX7301)	+= max7301.o
 obj-$(CONFIG_GPIO_MAX732X)	+= max732x.o
 obj-$(CONFIG_GPIO_MC33880)	+= mc33880.o

drivers/gpio/max7300.c

@@ -0,0 +1,94 @@
+/*
+ * drivers/gpio/max7300.c
+ *
+ * Copyright (C) 2009 Wolfram Sang, Pengutronix
+ *
+ * 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.
+ *
+ * Check max730x.c for further details.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/platform_device.h>
+#include <linux/mutex.h>
+#include <linux/i2c.h>
+#include <linux/spi/max7301.h>
+
+static int max7300_i2c_write(struct device *dev, unsigned int reg,
+				unsigned int val)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+
+	return i2c_smbus_write_byte_data(client, reg, val);
+}
+
+static int max7300_i2c_read(struct device *dev, unsigned int reg)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+
+	return i2c_smbus_read_byte_data(client, reg);
+}
+
+static int __devinit max7300_probe(struct i2c_client *client,
+			 const struct i2c_device_id *id)
+{
+	struct max7301 *ts;
+	int ret;
+
+	if (!i2c_check_functionality(client->adapter,
+			I2C_FUNC_SMBUS_BYTE_DATA))
+		return -EIO;
+
+	ts = kzalloc(sizeof(struct max7301), GFP_KERNEL);
+	if (!ts)
+		return -ENOMEM;
+
+	ts->read = max7300_i2c_read;
+	ts->write = max7300_i2c_write;
+	ts->dev = &client->dev;
+
+	ret = __max730x_probe(ts);
+	if (ret)
+		kfree(ts);
+	return ret;
+}
+
+static int __devexit max7300_remove(struct i2c_client *client)
+{
+	return __max730x_remove(&client->dev);
+}
+
+static const struct i2c_device_id max7300_id[] = {
+	{ "max7300", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, max7300_id);
+
+static struct i2c_driver max7300_driver = {
+	.driver = {
+		.name = "max7300",
+		.owner = THIS_MODULE,
+	},
+	.probe = max7300_probe,
+	.remove = __devexit_p(max7300_remove),
+	.id_table = max7300_id,
+};
+
+static int __init max7300_init(void)
+{
+	return i2c_add_driver(&max7300_driver);
+}
+subsys_initcall(max7300_init);
+
+static void __exit max7300_exit(void)
+{
+	i2c_del_driver(&max7300_driver);
+}
+module_exit(max7300_exit);
+
+MODULE_AUTHOR("Wolfram Sang");
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("MAX7300 GPIO-Expander");