/*
   * GPIO driver for the ACCES 104-IDIO-16 family
   * Copyright (C) 2015 William Breathitt Gray
   *
   * 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.
   *
   * This program is distributed in the hope that it will be useful, but
   * WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * General Public License for more details.

   *
   * This driver supports the following ACCES devices: 104-IDIO-16,
   * 104-IDIO-16E, 104-IDO-16, 104-IDIO-8, 104-IDIO-8E, and 104-IDO-8.

   */

  #include <linux/bitops.h>

  #include <linux/device.h>
  #include <linux/errno.h>
  #include <linux/gpio/driver.h>
  #include <linux/io.h>
  #include <linux/ioport.h>

  #include <linux/interrupt.h>
  #include <linux/irqdesc.h>

  #include <linux/isa.h>

  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/moduleparam.h>

  #include <linux/spinlock.h>

  #define IDIO_16_EXTENT 8
  #define MAX_NUM_IDIO_16 max_num_isa_dev(IDIO_16_EXTENT)
  
  static unsigned int base[MAX_NUM_IDIO_16];
  static unsigned int num_idio_16;
  module_param_array(base, uint, &num_idio_16, 0);
  MODULE_PARM_DESC(base, "ACCES 104-IDIO-16 base addresses");
  
  static unsigned int irq[MAX_NUM_IDIO_16];
  module_param_array(irq, uint, NULL, 0);
  MODULE_PARM_DESC(irq, "ACCES 104-IDIO-16 interrupt line numbers");

  
  /**
   * struct idio_16_gpio - GPIO device private data structure
   * @chip:	instance of the gpio_chip

   * @lock:	synchronization lock to prevent I/O race conditions
   * @irq_mask:	I/O bits affected by interrupts

   * @base:	base port address of the GPIO device

   * @irq:	Interrupt line number

   * @out_state:	output bits state
   */
  struct idio_16_gpio {
  	struct gpio_chip chip;
  	spinlock_t lock;

  	unsigned long irq_mask;

  	unsigned base;

  	unsigned irq;

  	unsigned out_state;
  };
  
  static int idio_16_gpio_get_direction(struct gpio_chip *chip, unsigned offset)
  {
  	if (offset > 15)
  		return 1;
  
  	return 0;
  }
  
  static int idio_16_gpio_direction_input(struct gpio_chip *chip, unsigned offset)
  {
  	return 0;
  }
  
  static int idio_16_gpio_direction_output(struct gpio_chip *chip,
  	unsigned offset, int value)
  {
  	chip->set(chip, offset, value);
  	return 0;
  }

  static int idio_16_gpio_get(struct gpio_chip *chip, unsigned offset)
  {

  	struct idio_16_gpio *const idio16gpio = gpiochip_get_data(chip);

  	const unsigned mask = BIT(offset-16);

  
  	if (offset < 16)
  		return -EINVAL;
  
  	if (offset < 24)

  		return !!(inb(idio16gpio->base + 1) & mask);

  	return !!(inb(idio16gpio->base + 5) & (mask>>8));

  }
  
  static void idio_16_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
  {

  	struct idio_16_gpio *const idio16gpio = gpiochip_get_data(chip);

  	const unsigned mask = BIT(offset);

  	unsigned long flags;
  
  	if (offset > 15)
  		return;
  
  	spin_lock_irqsave(&idio16gpio->lock, flags);
  
  	if (value)

  		idio16gpio->out_state |= mask;

  	else

  		idio16gpio->out_state &= ~mask;

  
  	if (offset > 7)
  		outb(idio16gpio->out_state >> 8, idio16gpio->base + 4);
  	else
  		outb(idio16gpio->out_state, idio16gpio->base);
  
  	spin_unlock_irqrestore(&idio16gpio->lock, flags);
  }

  static void idio_16_irq_ack(struct irq_data *data)
  {

  }
  
  static void idio_16_irq_mask(struct irq_data *data)
  {
  	struct gpio_chip *chip = irq_data_get_irq_chip_data(data);

  	struct idio_16_gpio *const idio16gpio = gpiochip_get_data(chip);

  	const unsigned long mask = BIT(irqd_to_hwirq(data));
  	unsigned long flags;
  
  	idio16gpio->irq_mask &= ~mask;
  
  	if (!idio16gpio->irq_mask) {
  		spin_lock_irqsave(&idio16gpio->lock, flags);
  
  		outb(0, idio16gpio->base + 2);
  
  		spin_unlock_irqrestore(&idio16gpio->lock, flags);
  	}
  }
  
  static void idio_16_irq_unmask(struct irq_data *data)
  {
  	struct gpio_chip *chip = irq_data_get_irq_chip_data(data);

  	struct idio_16_gpio *const idio16gpio = gpiochip_get_data(chip);

  	const unsigned long mask = BIT(irqd_to_hwirq(data));
  	const unsigned long prev_irq_mask = idio16gpio->irq_mask;
  	unsigned long flags;
  
  	idio16gpio->irq_mask |= mask;
  
  	if (!prev_irq_mask) {
  		spin_lock_irqsave(&idio16gpio->lock, flags);

  		inb(idio16gpio->base + 2);
  
  		spin_unlock_irqrestore(&idio16gpio->lock, flags);
  	}
  }
  
  static int idio_16_irq_set_type(struct irq_data *data, unsigned flow_type)
  {
  	/* The only valid irq types are none and both-edges */
  	if (flow_type != IRQ_TYPE_NONE &&
  		(flow_type & IRQ_TYPE_EDGE_BOTH) != IRQ_TYPE_EDGE_BOTH)
  		return -EINVAL;
  
  	return 0;
  }
  
  static struct irq_chip idio_16_irqchip = {
  	.name = "104-idio-16",
  	.irq_ack = idio_16_irq_ack,
  	.irq_mask = idio_16_irq_mask,
  	.irq_unmask = idio_16_irq_unmask,
  	.irq_set_type = idio_16_irq_set_type
  };
  
  static irqreturn_t idio_16_irq_handler(int irq, void *dev_id)
  {
  	struct idio_16_gpio *const idio16gpio = dev_id;
  	struct gpio_chip *const chip = &idio16gpio->chip;
  	int gpio;
  
  	for_each_set_bit(gpio, &idio16gpio->irq_mask, chip->ngpio)
  		generic_handle_irq(irq_find_mapping(chip->irqdomain, gpio));

  	spin_lock(&idio16gpio->lock);
  
  	outb(0, idio16gpio->base + 1);
  
  	spin_unlock(&idio16gpio->lock);

  	return IRQ_HANDLED;
  }

  static int idio_16_probe(struct device *dev, unsigned int id)

  {

  	struct idio_16_gpio *idio16gpio;

  	const char *const name = dev_name(dev);

  	int err;

  
  	idio16gpio = devm_kzalloc(dev, sizeof(*idio16gpio), GFP_KERNEL);
  	if (!idio16gpio)
  		return -ENOMEM;

  	if (!devm_request_region(dev, base[id], IDIO_16_EXTENT, name)) {

  		dev_err(dev, "Unable to lock port addresses (0x%X-0x%X)
  ",

  			base[id], base[id] + IDIO_16_EXTENT);

  		return -EBUSY;

  	}

  	idio16gpio->chip.label = name;

  	idio16gpio->chip.parent = dev;

  	idio16gpio->chip.owner = THIS_MODULE;
  	idio16gpio->chip.base = -1;
  	idio16gpio->chip.ngpio = 32;
  	idio16gpio->chip.get_direction = idio_16_gpio_get_direction;
  	idio16gpio->chip.direction_input = idio_16_gpio_direction_input;
  	idio16gpio->chip.direction_output = idio_16_gpio_direction_output;
  	idio16gpio->chip.get = idio_16_gpio_get;
  	idio16gpio->chip.set = idio_16_gpio_set;

  	idio16gpio->base = base[id];
  	idio16gpio->irq = irq[id];

  	idio16gpio->out_state = 0xFFFF;
  
  	spin_lock_init(&idio16gpio->lock);
  
  	dev_set_drvdata(dev, idio16gpio);

  	err = gpiochip_add_data(&idio16gpio->chip, idio16gpio);

  	if (err) {
  		dev_err(dev, "GPIO registering failed (%d)
  ", err);

  		return err;

  	}

  	/* Disable IRQ by default */

  	outb(0, base[id] + 2);
  	outb(0, base[id] + 1);

  	err = gpiochip_irqchip_add(&idio16gpio->chip, &idio_16_irqchip, 0,
  		handle_edge_irq, IRQ_TYPE_NONE);
  	if (err) {
  		dev_err(dev, "Could not add irqchip (%d)
  ", err);

  		goto err_gpiochip_remove;

  	}

  	err = request_irq(irq[id], idio_16_irq_handler, 0, name, idio16gpio);

  	if (err) {
  		dev_err(dev, "IRQ handler registering failed (%d)
  ", err);

  		goto err_gpiochip_remove;

  	}

  	return 0;

  err_gpiochip_remove:

  	gpiochip_remove(&idio16gpio->chip);

  	return err;
  }

  static int idio_16_remove(struct device *dev, unsigned int id)

  {

  	struct idio_16_gpio *const idio16gpio = dev_get_drvdata(dev);

  	free_irq(idio16gpio->irq, idio16gpio);

  	gpiochip_remove(&idio16gpio->chip);

  
  	return 0;
  }

  static struct isa_driver idio_16_driver = {
  	.probe = idio_16_probe,

  	.driver = {
  		.name = "104-idio-16"
  	},
  	.remove = idio_16_remove
  };

  module_isa_driver(idio_16_driver, num_idio_16);

  
  MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@gmail.com>");
  MODULE_DESCRIPTION("ACCES 104-IDIO-16 GPIO driver");

  MODULE_LICENSE("GPL v2");