/*
   *  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/of_gpio.h>

  #include <linux/slab.h>

  #include <linux/module.h>

  #define GEN_74X164_NUMBER_GPIOS	8

  struct gen_74x164_chip {
  	struct spi_device	*spi;

  	u8			*buffer;

  	struct gpio_chip	gpio_chip;
  	struct mutex		lock;

  	u32			registers;

  };

  static struct gen_74x164_chip *gpio_to_74x164_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)
  {

  	struct spi_message message;
  	struct spi_transfer *msg_buf;
  	int i, ret = 0;
  
  	msg_buf = kzalloc(chip->registers * sizeof(struct spi_transfer),
  			GFP_KERNEL);
  	if (!msg_buf)
  		return -ENOMEM;
  
  	spi_message_init(&message);
  
  	/*
  	 * Since the registers are chained, every byte sent will make
  	 * the previous byte shift to the next register in the
  	 * chain. Thus, the first byte send will end up in the last
  	 * register at the end of the transfer. So, to have a logical
  	 * numbering, send the bytes in reverse order so that the last
  	 * byte of the buffer will end up in the last register.
  	 */
  	for (i = chip->registers - 1; i >= 0; i--) {
  		msg_buf[i].tx_buf = chip->buffer +i;
  		msg_buf[i].len = sizeof(u8);
  		spi_message_add_tail(msg_buf + i, &message);
  	}
  
  	ret = spi_sync(chip->spi, &message);
  
  	kfree(msg_buf);
  
  	return ret;

  }

  static int gen_74x164_get_value(struct gpio_chip *gc, unsigned offset)
  {

  	struct gen_74x164_chip *chip = gpio_to_74x164_chip(gc);

  	u8 bank = offset / 8;
  	u8 pin = offset % 8;

  	int ret;
  
  	mutex_lock(&chip->lock);

  	ret = (chip->buffer[bank] >> pin) & 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_74x164_chip(gc);

  	u8 bank = offset / 8;
  	u8 pin = offset % 8;

  
  	mutex_lock(&chip->lock);
  	if (val)

  		chip->buffer[bank] |= (1 << pin);

  	else

  		chip->buffer[bank] &= ~(1 << pin);

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

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

  	if (!spi->dev.of_node) {
  		dev_err(&spi->dev, "No device tree data available.
  ");
  		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 = devm_kzalloc(&spi->dev, sizeof(*chip), GFP_KERNEL);

  	if (!chip)
  		return -ENOMEM;

  	pdata = spi->dev.platform_data;
  	if (pdata && pdata->base)
  		chip->gpio_chip.base = pdata->base;
  	else
  		chip->gpio_chip.base = -1;

  	mutex_init(&chip->lock);
  
  	dev_set_drvdata(&spi->dev, chip);
  
  	chip->spi = spi;

  	chip->gpio_chip.label = spi->modalias;
  	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;

  
  	if (of_property_read_u32(spi->dev.of_node, "registers-number", &chip->registers)) {
  		dev_err(&spi->dev, "Missing registers-number property in the DT.
  ");
  		ret = -EINVAL;
  		goto exit_destroy;
  	}
  
  	chip->gpio_chip.ngpio = GEN_74X164_NUMBER_GPIOS * chip->registers;

  	chip->buffer = devm_kzalloc(&spi->dev, chip->registers, GFP_KERNEL);

  	if (!chip->buffer) {
  		ret = -ENOMEM;
  		goto exit_destroy;
  	}

  	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
  ", 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);

  	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);

  	else

  		dev_err(&spi->dev, "Failed to remove the GPIO controller: %d
  ",
  				ret);
  
  	return ret;
  }

  static const struct of_device_id gen_74x164_dt_ids[] = {
  	{ .compatible = "fairchild,74hc595" },
  	{},
  };
  MODULE_DEVICE_TABLE(of, gen_74x164_dt_ids);

  static struct spi_driver gen_74x164_driver = {
  	.driver = {

  		.name		= "74x164",

  		.owner		= THIS_MODULE,

  		.of_match_table	= of_match_ptr(gen_74x164_dt_ids),

  	},
  	.probe		= gen_74x164_probe,
  	.remove		= __devexit_p(gen_74x164_remove),
  };

  module_spi_driver(gen_74x164_driver);

  
  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");