/*
   *  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/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 gpio_chip	gpio_chip;
  	struct mutex		lock;

  	u32			registers;

  	/*
  	 * 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 sent will end up in the last
  	 * register at the end of the transfer. So, to have a logical
  	 * numbering, store the bytes in reverse order.
  	 */

  	u8			buffer[0];

  };

  static int __gen_74x164_write_config(struct gen_74x164_chip *chip)
  {

  	return spi_write(to_spi_device(chip->gpio_chip.parent), chip->buffer,
  			 chip->registers);

  }

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

  	struct gen_74x164_chip *chip = gpiochip_get_data(gc);

  	u8 bank = chip->registers - 1 - 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 = gpiochip_get_data(gc);

  	u8 bank = chip->registers - 1 - 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 void gen_74x164_set_multiple(struct gpio_chip *gc, unsigned long *mask,
  				    unsigned long *bits)
  {
  	struct gen_74x164_chip *chip = gpiochip_get_data(gc);
  	unsigned int i, idx, shift;
  	u8 bank, bankmask;
  
  	mutex_lock(&chip->lock);
  	for (i = 0, bank = chip->registers - 1; i < chip->registers;
  	     i++, bank--) {
  		idx = i / sizeof(*mask);
  		shift = i % sizeof(*mask) * BITS_PER_BYTE;
  		bankmask = mask[idx] >> shift;
  		if (!bankmask)
  			continue;
  
  		chip->buffer[bank] &= ~bankmask;
  		chip->buffer[bank] |= bankmask & (bits[idx] >> shift);
  	}
  	__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 gen_74x164_probe(struct spi_device *spi)

  {
  	struct gen_74x164_chip *chip;

  	u32 nregs;

  	int ret;

  	/*
  	 * bits_per_word cannot be configured in platform data
  	 */
  	spi->bits_per_word = 8;
  
  	ret = spi_setup(spi);
  	if (ret < 0)
  		return ret;

  	if (of_property_read_u32(spi->dev.of_node, "registers-number",
  				 &nregs)) {
  		dev_err(&spi->dev,
  			"Missing registers-number property in the DT.
  ");
  		return -EINVAL;
  	}
  
  	chip = devm_kzalloc(&spi->dev, sizeof(*chip) + nregs, GFP_KERNEL);

  	if (!chip)
  		return -ENOMEM;

  	spi_set_drvdata(spi, chip);

  	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;

  	chip->gpio_chip.set_multiple = gen_74x164_set_multiple;

  	chip->gpio_chip.base = -1;

  	chip->registers = nregs;

  	chip->gpio_chip.ngpio = GEN_74X164_NUMBER_GPIOS * chip->registers;

  	of_property_read_u8_array(spi->dev.of_node, "registers-default",
  				 chip->buffer, chip->registers);

  	chip->gpio_chip.can_sleep = true;

  	chip->gpio_chip.parent = &spi->dev;

  	chip->gpio_chip.owner = THIS_MODULE;

  	mutex_init(&chip->lock);

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

  	ret = gpiochip_add_data(&chip->gpio_chip, chip);

  	if (!ret)
  		return 0;

  
  exit_destroy:

  	mutex_destroy(&chip->lock);

  	return ret;
  }

  static int gen_74x164_remove(struct spi_device *spi)

  {

  	struct gen_74x164_chip *chip = spi_get_drvdata(spi);

  	gpiochip_remove(&chip->gpio_chip);
  	mutex_destroy(&chip->lock);

  	return 0;

  }

  static const struct of_device_id gen_74x164_dt_ids[] = {
  	{ .compatible = "fairchild,74hc595" },

  	{ .compatible = "nxp,74lvc594" },

  	{},
  };
  MODULE_DEVICE_TABLE(of, gen_74x164_dt_ids);

  static struct spi_driver gen_74x164_driver = {
  	.driver = {

  		.name		= "74x164",

  		.of_match_table	= gen_74x164_dt_ids,

  	},
  	.probe		= gen_74x164_probe,

  	.remove		= 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");