LXR linux/drivers/gpio/max7301.c

   1/*
   2 * drivers/gpio/max7301.c
   3 *
   4 * Copyright (C) 2006 Juergen Beisert, Pengutronix
   5 * Copyright (C) 2008 Guennadi Liakhovetski, Pengutronix
   6 * Copyright (C) 2009 Wolfram Sang, Pengutronix
   7 *
   8 * This program is free software; you can redistribute it and/or modify
   9 * it under the terms of the GNU General Public License version 2 as
  10 * published by the Free Software Foundation.
  11 *
  12 * Check max730x.c for further details.
  13 */
  14
  15#include <linux/module.h>
  16#include <linux/init.h>
  17#include <linux/platform_device.h>
  18#include <linux/mutex.h>
  19#include <linux/slab.h>
  20#include <linux/spi/spi.h>
  21#include <linux/spi/max7301.h>
  22
  23/* A write to the MAX7301 means one message with one transfer */
  24static int max7301_spi_write(struct device *dev, unsigned int reg,
  25                                unsigned int val)
  26{
  27        struct spi_device *spi = to_spi_device(dev);
  28        u16 word = ((reg & 0x7F) << 8) | (val & 0xFF);
  29
  30        return spi_write(spi, (const u8 *)&word, sizeof(word));
  31}
  32
  33/* A read from the MAX7301 means two transfers; here, one message each */
  34
  35static int max7301_spi_read(struct device *dev, unsigned int reg)
  36{
  37        int ret;
  38        u16 word;
  39        struct spi_device *spi = to_spi_device(dev);
  40
  41        word = 0x8000 | (reg << 8);
  42        ret = spi_write(spi, (const u8 *)&word, sizeof(word));
  43        if (ret)
  44                return ret;
  45        /*
  46         * This relies on the fact, that a transfer with NULL tx_buf shifts out
  47         * zero bytes (=NOOP for MAX7301)
  48         */
  49        ret = spi_read(spi, (u8 *)&word, sizeof(word));
  50        if (ret)
  51                return ret;
  52        return word & 0xff;
  53}
  54
  55static int __devinit max7301_probe(struct spi_device *spi)
  56{
  57        struct max7301 *ts;
  58        int ret;
  59
  60        /* bits_per_word cannot be configured in platform data */
  61        spi->bits_per_word = 16;
  62        ret = spi_setup(spi);
  63        if (ret < 0)
  64                return ret;
  65
  66        ts = kzalloc(sizeof(struct max7301), GFP_KERNEL);
  67        if (!ts)
  68                return -ENOMEM;
  69
  70        ts->read = max7301_spi_read;
  71        ts->write = max7301_spi_write;
  72        ts->dev = &spi->dev;
  73
  74        ret = __max730x_probe(ts);
  75        if (ret)
  76                kfree(ts);
  77        return ret;
  78}
  79
  80static int __devexit max7301_remove(struct spi_device *spi)
  81{
  82        return __max730x_remove(&spi->dev);
  83}
  84
  85static const struct spi_device_id max7301_id[] = {
  86        { "max7301", 0 },
  87        { }
  88};
  89MODULE_DEVICE_TABLE(spi, max7301_id);
  90
  91static struct spi_driver max7301_driver = {
  92        .driver = {
  93                .name = "max7301",
  94                .owner = THIS_MODULE,
  95        },
  96        .probe = max7301_probe,
  97        .remove = __devexit_p(max7301_remove),
  98        .id_table = max7301_id,
  99};
 100
 101static int __init max7301_init(void)
 102{
 103        return spi_register_driver(&max7301_driver);
 104}
 105/* register after spi postcore initcall and before
 106 * subsys initcalls that may rely on these GPIOs
 107 */
 108subsys_initcall(max7301_init);
 109
 110static void __exit max7301_exit(void)
 111{
 112        spi_unregister_driver(&max7301_driver);
 113}
 114module_exit(max7301_exit);
 115
 116MODULE_AUTHOR("Juergen Beisert, Wolfram Sang");
 117MODULE_LICENSE("GPL v2");
 118MODULE_DESCRIPTION("MAX7301 GPIO-Expander");
 119