drivers/gpio/74x164.c

/*
 *  74Hx164 - Generic serial-in/parallel-out 8-bits shift register GPIO driver
 *
 *  Copyright (C) 2010 Gabor Juhos <juhosg@openwrt.org>
 *  Copyright (C) 2010 Miguel Gaio <miguel.gaio@efixo.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/init.h>
#include <linux/mutex.h>
#include <linux/spi/spi.h>
#include <linux/spi/74x164.h>
#include <linux/gpio.h>
#include <linux/slab.h>

#define GEN_74X164_GPIO_COUNT	8


struct gen_74x164_chip {
	struct spi_device	*spi;
	struct gpio_chip	gpio_chip;
	struct mutex		lock;
	u8			port_config;
};

static void gen_74x164_set_value(struct gpio_chip *, unsigned, int);

static struct gen_74x164_chip *gpio_to_chip(struct gpio_chip *gc)
{
	return container_of(gc, struct gen_74x164_chip, gpio_chip);
}

static int __gen_74x164_write_config(struct gen_74x164_chip *chip)
{
	return spi_write(chip->spi,
			 &chip->port_config, sizeof(chip->port_config));
}

static int gen_74x164_direction_output(struct gpio_chip *gc,
		unsigned offset, int val)
{
	gen_74x164_set_value(gc, offset, val);
	return 0;
}

static int gen_74x164_get_value(struct gpio_chip *gc, unsigned offset)
{
	struct gen_74x164_chip *chip = gpio_to_chip(gc);
	int ret;

	mutex_lock(&chip->lock);
	ret = (chip->port_config >> offset) & 0x1;
	mutex_unlock(&chip->lock);

	return ret;
}

static void gen_74x164_set_value(struct gpio_chip *gc,
		unsigned offset, int val)
{
	struct gen_74x164_chip *chip = gpio_to_chip(gc);

	mutex_lock(&chip->lock);
	if (val)
		chip->port_config |= (1 << offset);
	else
		chip->port_config &= ~(1 << offset);

	__gen_74x164_write_config(chip);
	mutex_unlock(&chip->lock);
}

static int __devinit gen_74x164_probe(struct spi_device *spi)
{
	struct gen_74x164_chip *chip;
	struct gen_74x164_chip_platform_data *pdata;
	int ret;

	pdata = spi->dev.platform_data;
	if (!pdata || !pdata->base) {
		dev_dbg(&spi->dev, "incorrect or missing platform data\n");
		return -EINVAL;
	}

	/*
	 * bits_per_word cannot be configured in platform data
	 */
	spi->bits_per_word = 8;

	ret = spi_setup(spi);
	if (ret < 0)
		return ret;

	chip = kzalloc(sizeof(*chip), GFP_KERNEL);
	if (!chip)
		return -ENOMEM;

	mutex_init(&chip->lock);

	dev_set_drvdata(&spi->dev, chip);

	chip->spi = spi;

	chip->gpio_chip.label = GEN_74X164_DRIVER_NAME,
		chip->gpio_chip.direction_output = gen_74x164_direction_output;
	chip->gpio_chip.get = gen_74x164_get_value;
	chip->gpio_chip.set = gen_74x164_set_value;
	chip->gpio_chip.base = pdata->base;
	chip->gpio_chip.ngpio = GEN_74X164_GPIO_COUNT;
	chip->gpio_chip.can_sleep = 1;
	chip->gpio_chip.dev = &spi->dev;
	chip->gpio_chip.owner = THIS_MODULE;

	ret = __gen_74x164_write_config(chip);
	if (ret) {
		dev_err(&spi->dev, "Failed writing: %d\n", ret);
		goto exit_destroy;
	}

	ret = gpiochip_add(&chip->gpio_chip);
	if (ret)
		goto exit_destroy;

	return ret;

exit_destroy:
	dev_set_drvdata(&spi->dev, NULL);
	mutex_destroy(&chip->lock);
	kfree(chip);
	return ret;
}

static int gen_74x164_remove(struct spi_device *spi)
{
	struct gen_74x164_chip *chip;
	int ret;

	chip = dev_get_drvdata(&spi->dev);
	if (chip == NULL)
		return -ENODEV;

	dev_set_drvdata(&spi->dev, NULL);

	ret = gpiochip_remove(&chip->gpio_chip);
	if (!ret) {
		mutex_destroy(&chip->lock);
		kfree(chip);
	} else
		dev_err(&spi->dev, "Failed to remove the GPIO controller: %d\n",
				ret);

	return ret;
}

static struct spi_driver gen_74x164_driver = {
	.driver = {
		.name		= GEN_74X164_DRIVER_NAME,
		.owner		= THIS_MODULE,
	},
	.probe		= gen_74x164_probe,
	.remove		= __devexit_p(gen_74x164_remove),
};

static int __init gen_74x164_init(void)
{
	return spi_register_driver(&gen_74x164_driver);
}
subsys_initcall(gen_74x164_init);

static void __exit gen_74x164_exit(void)
{
	spi_unregister_driver(&gen_74x164_driver);
}
module_exit(gen_74x164_exit);

MODULE_AUTHOR("Gabor Juhos <juhosg@openwrt.org>");
MODULE_AUTHOR("Miguel Gaio <miguel.gaio@efixo.com>");
MODULE_DESCRIPTION("GPIO expander driver for 74X164 8-bits shift register");
MODULE_LICENSE("GPL v2");