gpio-max7301.c

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/*
 * 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.
 *
 * Check max730x.c for further details.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/spi/spi.h>
#include <linux/spi/max7301.h>

/* A write to the MAX7301 means one message with one transfer */
static int max7301_spi_write(struct device *dev, unsigned int reg,
                unsigned int val)
{
    struct spi_device *spi = to_spi_device(dev);
    u16 word = ((reg & 0x7F) << 8) | (val & 0xFF);

    return spi_write(spi, (const u8 *)&word, sizeof(word));
}

/* A read from the MAX7301 means two transfers; here, one message each */

static int max7301_spi_read(struct device *dev, unsigned int reg)
{
    int ret;
    u16 word;
    struct spi_device *spi = to_spi_device(dev);

    word = 0x8000 | (reg << 8);
    ret = spi_write(spi, (const u8 *)&word, sizeof(word));
    if (ret)
        return ret;
    /*
     * This relies on the fact, that a transfer with NULL tx_buf shifts out
     * zero bytes (=NOOP for MAX7301)
     */
    ret = spi_read(spi, (u8 *)&word, sizeof(word));
    if (ret)
        return ret;
    return word & 0xff;
}

static int __devinit max7301_probe(struct spi_device *spi)
{
    struct max7301 *ts;
    int ret;

    /* bits_per_word cannot be configured in platform data */
    spi->bits_per_word = 16;
    ret = spi_setup(spi);
    if (ret < 0)
        return ret;

    ts = kzalloc(sizeof(struct max7301), GFP_KERNEL);
    if (!ts)
        return -ENOMEM;

    ts->read = max7301_spi_read;
    ts->write = max7301_spi_write;
    ts->dev = &spi->dev;

    ret = __max730x_probe(ts);
    if (ret)
        kfree(ts);
    return ret;
}

static int __devexit max7301_remove(struct spi_device *spi)
{
    return __max730x_remove(&spi->dev);
}

static const struct spi_device_id max7301_id[] = {
    { "max7301", 0 },
    { }
};
MODULE_DEVICE_TABLE(spi, max7301_id);

static struct spi_driver max7301_driver = {
    .driver = {
        .name = "max7301",
        .owner = THIS_MODULE,
    },
    .probe = max7301_probe,
    .remove = __devexit_p(max7301_remove),
    .id_table = max7301_id,
};

static int __init max7301_init(void)
{
    return spi_register_driver(&max7301_driver);
}
/* register after spi postcore initcall and before
 * subsys initcalls that may rely on these GPIOs
 */
subsys_initcall(max7301_init);

static void __exit max7301_exit(void)
{
    spi_unregister_driver(&max7301_driver);
}
module_exit(max7301_exit);

MODULE_AUTHOR("Juergen Beisert, Wolfram Sang");
MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("MAX7301 GPIO-Expander");