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