/**
   * Copyright (C) 2006 Juergen Beisert, Pengutronix
   * Copyright (C) 2008 Guennadi Liakhovetski, Pengutronix
   * Copyright (C) 2009 Wolfram Sang, Pengutronix
   *
   * 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.
   *
   * The Maxim MAX7300/1 device is an I2C/SPI driven GPIO expander. There are
   * 28 GPIOs. 8 of them can trigger an interrupt. See datasheet for more
   * details
   * Note:
   * - DIN must be stable at the rising edge of clock.
   * - when writing:
   *   - always clock in 16 clocks at once
   *   - at DIN: D15 first, D0 last
   *   - D0..D7 = databyte, D8..D14 = commandbyte
   *   - D15 = low -> write command
   * - when reading
   *   - always clock in 16 clocks at once
   *   - at DIN: D15 first, D0 last
   *   - D0..D7 = dummy, D8..D14 = register address
   *   - D15 = high -> read command
   *   - raise CS and assert it again
   *   - always clock in 16 clocks at once
   *   - at DOUT: D15 first, D0 last
   *   - D0..D7 contains the data from the first cycle
   *
   * The driver exports a standard gpiochip interface
   */
  
  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/platform_device.h>
  #include <linux/mutex.h>
  #include <linux/spi/max7301.h>
  #include <linux/gpio.h>
  #include <linux/slab.h>
  
  /*
   * Pin configurations, see MAX7301 datasheet page 6
   */
  #define PIN_CONFIG_MASK 0x03
  #define PIN_CONFIG_IN_PULLUP 0x03
  #define PIN_CONFIG_IN_WO_PULLUP 0x02
  #define PIN_CONFIG_OUT 0x01
  
  #define PIN_NUMBER 28
  
  static int max7301_direction_input(struct gpio_chip *chip, unsigned offset)
  {
  	struct max7301 *ts = container_of(chip, struct max7301, chip);
  	u8 *config;
  	u8 offset_bits, pin_config;
  	int ret;
  
  	/* First 4 pins are unused in the controller */
  	offset += 4;
  	offset_bits = (offset & 3) << 1;
  
  	config = &ts->port_config[offset >> 2];
  
  	if (ts->input_pullup_active & BIT(offset))
  		pin_config = PIN_CONFIG_IN_PULLUP;
  	else
  		pin_config = PIN_CONFIG_IN_WO_PULLUP;
  
  	mutex_lock(&ts->lock);
  
  	*config = (*config & ~(PIN_CONFIG_MASK << offset_bits))
  			   | (pin_config << offset_bits);
  
  	ret = ts->write(ts->dev, 0x08 + (offset >> 2), *config);
  
  	mutex_unlock(&ts->lock);
  
  	return ret;
  }
  
  static int __max7301_set(struct max7301 *ts, unsigned offset, int value)
  {
  	if (value) {
  		ts->out_level |= 1 << offset;
  		return ts->write(ts->dev, 0x20 + offset, 0x01);
  	} else {
  		ts->out_level &= ~(1 << offset);
  		return ts->write(ts->dev, 0x20 + offset, 0x00);
  	}
  }
  
  static int max7301_direction_output(struct gpio_chip *chip, unsigned offset,
  				    int value)
  {
  	struct max7301 *ts = container_of(chip, struct max7301, chip);
  	u8 *config;
  	u8 offset_bits;
  	int ret;
  
  	/* First 4 pins are unused in the controller */
  	offset += 4;
  	offset_bits = (offset & 3) << 1;
  
  	config = &ts->port_config[offset >> 2];
  
  	mutex_lock(&ts->lock);
  
  	*config = (*config & ~(PIN_CONFIG_MASK << offset_bits))
  			   | (PIN_CONFIG_OUT << offset_bits);
  
  	ret = __max7301_set(ts, offset, value);
  
  	if (!ret)
  		ret = ts->write(ts->dev, 0x08 + (offset >> 2), *config);
  
  	mutex_unlock(&ts->lock);
  
  	return ret;
  }
  
  static int max7301_get(struct gpio_chip *chip, unsigned offset)
  {
  	struct max7301 *ts = container_of(chip, struct max7301, chip);
  	int config, level = -EINVAL;
  
  	/* First 4 pins are unused in the controller */
  	offset += 4;
  
  	mutex_lock(&ts->lock);
  
  	config = (ts->port_config[offset >> 2] >> ((offset & 3) << 1))
  			& PIN_CONFIG_MASK;
  
  	switch (config) {
  	case PIN_CONFIG_OUT:
  		/* Output: return cached level */
  		level =  !!(ts->out_level & (1 << offset));
  		break;
  	case PIN_CONFIG_IN_WO_PULLUP:
  	case PIN_CONFIG_IN_PULLUP:
  		/* Input: read out */
  		level = ts->read(ts->dev, 0x20 + offset) & 0x01;
  	}
  	mutex_unlock(&ts->lock);
  
  	return level;
  }
  
  static void max7301_set(struct gpio_chip *chip, unsigned offset, int value)
  {
  	struct max7301 *ts = container_of(chip, struct max7301, chip);
  
  	/* First 4 pins are unused in the controller */
  	offset += 4;
  
  	mutex_lock(&ts->lock);
  
  	__max7301_set(ts, offset, value);
  
  	mutex_unlock(&ts->lock);
  }
  
  int __max730x_probe(struct max7301 *ts)
  {
  	struct device *dev = ts->dev;
  	struct max7301_platform_data *pdata;
  	int i, ret;
  
  	pdata = dev_get_platdata(dev);
  
  	mutex_init(&ts->lock);
  	dev_set_drvdata(dev, ts);
  
  	/* Power up the chip and disable IRQ output */
  	ts->write(dev, 0x04, 0x01);
  
  	if (pdata) {
  		ts->input_pullup_active = pdata->input_pullup_active;
  		ts->chip.base = pdata->base;
  	} else {
  		ts->chip.base = -1;
  	}
  	ts->chip.label = dev->driver->name;
  
  	ts->chip.direction_input = max7301_direction_input;
  	ts->chip.get = max7301_get;
  	ts->chip.direction_output = max7301_direction_output;
  	ts->chip.set = max7301_set;
  
  	ts->chip.ngpio = PIN_NUMBER;
  	ts->chip.can_sleep = true;
  	ts->chip.dev = dev;
  	ts->chip.owner = THIS_MODULE;
  
  	/*
  	 * initialize pullups according to platform data and cache the
  	 * register values for later use.
  	 */
  	for (i = 1; i < 8; i++) {
  		int j;
  		/*
  		 * initialize port_config with "0xAA", which means
  		 * input with internal pullup disabled. This is needed
  		 * to avoid writing zeros (in the inner for loop),
  		 * which is not allowed according to the datasheet.
  		 */
  		ts->port_config[i] = 0xAA;
  		for (j = 0; j < 4; j++) {
  			int offset = (i - 1) * 4 + j;
  			ret = max7301_direction_input(&ts->chip, offset);
  			if (ret)
  				goto exit_destroy;
  		}
  	}
  
  	ret = gpiochip_add(&ts->chip);
  	if (ret)
  		goto exit_destroy;
  
  	return ret;
  
  exit_destroy:
  	mutex_destroy(&ts->lock);
  	return ret;
  }
  EXPORT_SYMBOL_GPL(__max730x_probe);
  
  int __max730x_remove(struct device *dev)
  {
  	struct max7301 *ts = dev_get_drvdata(dev);
  	int ret;
  
  	if (ts == NULL)
  		return -ENODEV;
  
  	/* Power down the chip and disable IRQ output */
  	ts->write(dev, 0x04, 0x00);
  
  	ret = gpiochip_remove(&ts->chip);
  	if (!ret) {
  		mutex_destroy(&ts->lock);
  		kfree(ts);
  	} else
  		dev_err(dev, "Failed to remove GPIO controller: %d
  ", ret);
  
  	return ret;
  }
  EXPORT_SYMBOL_GPL(__max730x_remove);
  
  MODULE_AUTHOR("Juergen Beisert, Wolfram Sang");
  MODULE_LICENSE("GPL v2");
  MODULE_DESCRIPTION("MAX730x GPIO-Expanders, generic parts");