gpio-74x164.c

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/*
 *  74Hx164 - Generic serial-in/parallel-out 8-bits shift register GPIO driver
 *
 *  Copyright (C) 2010 Gabor Juhos <[email protected]>
 *  Copyright (C) 2010 Miguel Gaio <[email protected]>
 *
 *  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.\n");
        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.\n");
        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\n", 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\n",
                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 <[email protected]>");
MODULE_AUTHOR("Miguel Gaio <[email protected]>");
MODULE_DESCRIPTION("GPIO expander driver for 74X164 8-bits shift register");
MODULE_LICENSE("GPL v2");