/*
   * TI/National Semiconductor LP3943 GPIO driver
   *
   * Copyright 2013 Texas Instruments
   *
   * Author: Milo Kim <milo.kim@ti.com>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; version 2.
   */
  
  #include <linux/bitops.h>
  #include <linux/err.h>
  #include <linux/gpio.h>
  #include <linux/i2c.h>
  #include <linux/mfd/lp3943.h>
  #include <linux/module.h>
  #include <linux/platform_device.h>
  #include <linux/slab.h>
  
  enum lp3943_gpios {
  	LP3943_GPIO1,
  	LP3943_GPIO2,
  	LP3943_GPIO3,
  	LP3943_GPIO4,
  	LP3943_GPIO5,
  	LP3943_GPIO6,
  	LP3943_GPIO7,
  	LP3943_GPIO8,
  	LP3943_GPIO9,
  	LP3943_GPIO10,
  	LP3943_GPIO11,
  	LP3943_GPIO12,
  	LP3943_GPIO13,
  	LP3943_GPIO14,
  	LP3943_GPIO15,
  	LP3943_GPIO16,
  	LP3943_MAX_GPIO,
  };
  
  struct lp3943_gpio {
  	struct gpio_chip chip;
  	struct lp3943 *lp3943;
  	u16 input_mask;		/* 1 = GPIO is input direction, 0 = output */
  };
  
  static inline struct lp3943_gpio *to_lp3943_gpio(struct gpio_chip *_chip)
  {
  	return container_of(_chip, struct lp3943_gpio, chip);
  }
  
  static int lp3943_gpio_request(struct gpio_chip *chip, unsigned offset)
  {
  	struct lp3943_gpio *lp3943_gpio = to_lp3943_gpio(chip);
  	struct lp3943 *lp3943 = lp3943_gpio->lp3943;
  
  	/* Return an error if the pin is already assigned */
  	if (test_and_set_bit(offset, &lp3943->pin_used))
  		return -EBUSY;
  
  	return 0;
  }
  
  static void lp3943_gpio_free(struct gpio_chip *chip, unsigned offset)
  {
  	struct lp3943_gpio *lp3943_gpio = to_lp3943_gpio(chip);
  	struct lp3943 *lp3943 = lp3943_gpio->lp3943;
  
  	clear_bit(offset, &lp3943->pin_used);
  }
  
  static int lp3943_gpio_set_mode(struct lp3943_gpio *lp3943_gpio, u8 offset,
  				u8 val)
  {
  	struct lp3943 *lp3943 = lp3943_gpio->lp3943;
  	const struct lp3943_reg_cfg *mux = lp3943->mux_cfg;
  
  	return lp3943_update_bits(lp3943, mux[offset].reg, mux[offset].mask,
  				  val << mux[offset].shift);
  }
  
  static int lp3943_gpio_direction_input(struct gpio_chip *chip, unsigned offset)
  {
  	struct lp3943_gpio *lp3943_gpio = to_lp3943_gpio(chip);
  
  	lp3943_gpio->input_mask |= BIT(offset);
  
  	return lp3943_gpio_set_mode(lp3943_gpio, offset, LP3943_GPIO_IN);
  }
  
  static int lp3943_get_gpio_in_status(struct lp3943_gpio *lp3943_gpio,
  				     struct gpio_chip *chip, unsigned offset)
  {
  	u8 addr, read;
  	int err;
  
  	switch (offset) {
  	case LP3943_GPIO1 ... LP3943_GPIO8:
  		addr = LP3943_REG_GPIO_A;
  		break;
  	case LP3943_GPIO9 ... LP3943_GPIO16:
  		addr = LP3943_REG_GPIO_B;
  		offset = offset - 8;
  		break;
  	default:
  		return -EINVAL;
  	}
  
  	err = lp3943_read_byte(lp3943_gpio->lp3943, addr, &read);
  	if (err)
  		return err;
  
  	return !!(read & BIT(offset));
  }
  
  static int lp3943_get_gpio_out_status(struct lp3943_gpio *lp3943_gpio,
  				      struct gpio_chip *chip, unsigned offset)
  {
  	struct lp3943 *lp3943 = lp3943_gpio->lp3943;
  	const struct lp3943_reg_cfg *mux = lp3943->mux_cfg;
  	u8 read;
  	int err;
  
  	err = lp3943_read_byte(lp3943, mux[offset].reg, &read);
  	if (err)
  		return err;
  
  	read = (read & mux[offset].mask) >> mux[offset].shift;
  
  	if (read == LP3943_GPIO_OUT_HIGH)
  		return 1;
  	else if (read == LP3943_GPIO_OUT_LOW)
  		return 0;
  	else
  		return -EINVAL;
  }
  
  static int lp3943_gpio_get(struct gpio_chip *chip, unsigned offset)
  {
  	struct lp3943_gpio *lp3943_gpio = to_lp3943_gpio(chip);
  
  	/*
  	 * Limitation:
  	 *   LP3943 doesn't have the GPIO direction register. It provides
  	 *   only input and output status registers.
  	 *   So, direction info is required to handle the 'get' operation.
  	 *   This variable is updated whenever the direction is changed and
  	 *   it is used here.
  	 */
  
  	if (lp3943_gpio->input_mask & BIT(offset))
  		return lp3943_get_gpio_in_status(lp3943_gpio, chip, offset);
  	else
  		return lp3943_get_gpio_out_status(lp3943_gpio, chip, offset);
  }
  
  static void lp3943_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
  {
  	struct lp3943_gpio *lp3943_gpio = to_lp3943_gpio(chip);
  	u8 data;
  
  	if (value)
  		data = LP3943_GPIO_OUT_HIGH;
  	else
  		data = LP3943_GPIO_OUT_LOW;
  
  	lp3943_gpio_set_mode(lp3943_gpio, offset, data);
  }
  
  static int lp3943_gpio_direction_output(struct gpio_chip *chip, unsigned offset,
  					int value)
  {
  	struct lp3943_gpio *lp3943_gpio = to_lp3943_gpio(chip);
  
  	lp3943_gpio_set(chip, offset, value);
  	lp3943_gpio->input_mask &= ~BIT(offset);
  
  	return 0;
  }
  
  static const struct gpio_chip lp3943_gpio_chip = {
  	.label			= "lp3943",
  	.owner			= THIS_MODULE,
  	.request		= lp3943_gpio_request,
  	.free			= lp3943_gpio_free,
  	.direction_input	= lp3943_gpio_direction_input,
  	.get			= lp3943_gpio_get,
  	.direction_output	= lp3943_gpio_direction_output,
  	.set			= lp3943_gpio_set,
  	.base			= -1,
  	.ngpio			= LP3943_MAX_GPIO,
  	.can_sleep		= 1,
  };
  
  static int lp3943_gpio_probe(struct platform_device *pdev)
  {
  	struct lp3943 *lp3943 = dev_get_drvdata(pdev->dev.parent);
  	struct lp3943_gpio *lp3943_gpio;
  
  	lp3943_gpio = devm_kzalloc(&pdev->dev, sizeof(*lp3943_gpio),
  				GFP_KERNEL);
  	if (!lp3943_gpio)
  		return -ENOMEM;
  
  	lp3943_gpio->lp3943 = lp3943;
  	lp3943_gpio->chip = lp3943_gpio_chip;
  	lp3943_gpio->chip.dev = &pdev->dev;
  
  	platform_set_drvdata(pdev, lp3943_gpio);
  
  	return gpiochip_add(&lp3943_gpio->chip);
  }
  
  static int lp3943_gpio_remove(struct platform_device *pdev)
  {
  	struct lp3943_gpio *lp3943_gpio = platform_get_drvdata(pdev);
  
  	return gpiochip_remove(&lp3943_gpio->chip);
  }
  
  static const struct of_device_id lp3943_gpio_of_match[] = {
  	{ .compatible = "ti,lp3943-gpio", },
  	{ }
  };
  MODULE_DEVICE_TABLE(of, lp3943_gpio_of_match);
  
  static struct platform_driver lp3943_gpio_driver = {
  	.probe = lp3943_gpio_probe,
  	.remove = lp3943_gpio_remove,
  	.driver = {
  		.name = "lp3943-gpio",
  		.owner = THIS_MODULE,
  		.of_match_table = lp3943_gpio_of_match,
  	},
  };
  module_platform_driver(lp3943_gpio_driver);
  
  MODULE_DESCRIPTION("LP3943 GPIO driver");
  MODULE_ALIAS("platform:lp3943-gpio");
  MODULE_AUTHOR("Milo Kim");
  MODULE_LICENSE("GPL");