text: /*
   *  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 __devexit 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");
  