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 */
  24 static 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
  35 static 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
  55 static 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
  80 static int __devexit max7301_remove(struct spi_device *spi)
  81 {
  82         return __max730x_remove(&spi->dev);
  83 }
  84
  85 static const struct spi_device_id max7301_id[] = {
  86         { "max7301", 0 },
  87         { }
  88 };
  89 MODULE_DEVICE_TABLE(spi, max7301_id);
  90
  91 static 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
 101 static 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  */
 108 subsys_initcall(max7301_init);
 109
 110 static void __exit max7301_exit(void)
 111 {
 112         spi_unregister_driver(&max7301_driver);
 113 }
 114 module_exit(max7301_exit);
 115
 116 MODULE_AUTHOR("Juergen Beisert, Wolfram Sang");
 117 MODULE_LICENSE("GPL v2");
 118 MODULE_DESCRIPTION("MAX7301 GPIO-Expander");