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/spi/spi.h>
  20 #include <linux/spi/max7301.h>
  21
  22 /* A write to the MAX7301 means one message with one transfer */
  23 static int max7301_spi_write(struct device *dev, unsigned int reg,
  24                                 unsigned int val)
  25 {
  26         struct spi_device *spi = to_spi_device(dev);
  27         u16 word = ((reg & 0x7F) << 8) | (val & 0xFF);
  28
  29         return spi_write(spi, (const u8 *)&word, sizeof(word));
  30 }
  31
  32 /* A read from the MAX7301 means two transfers; here, one message each */
  33
  34 static int max7301_spi_read(struct device *dev, unsigned int reg)
  35 {
  36         int ret;
  37         u16 word;
  38         struct spi_device *spi = to_spi_device(dev);
  39
  40         word = 0x8000 | (reg << 8);
  41         ret = spi_write(spi, (const u8 *)&word, sizeof(word));
  42         if (ret)
  43                 return ret;
  44         /*
  45          * This relies on the fact, that a transfer with NULL tx_buf shifts out
  46          * zero bytes (=NOOP for MAX7301)
  47          */
  48         ret = spi_read(spi, (u8 *)&word, sizeof(word));
  49         if (ret)
  50                 return ret;
  51         return word & 0xff;
  52 }
  53
  54 static int __devinit max7301_probe(struct spi_device *spi)
  55 {
  56         struct max7301 *ts;
  57         int ret;
  58
  59         /* bits_per_word cannot be configured in platform data */
  60         spi->bits_per_word = 16;
  61         ret = spi_setup(spi);
  62         if (ret < 0)
  63                 return ret;
  64
  65         ts = kzalloc(sizeof(struct max7301), GFP_KERNEL);
  66         if (!ts)
  67                 return -ENOMEM;
  68
  69         ts->read = max7301_spi_read;
  70         ts->write = max7301_spi_write;
  71         ts->dev = &spi->dev;
  72
  73         ret = __max730x_probe(ts);
  74         if (ret)
  75                 kfree(ts);
  76         return ret;
  77 }
  78
  79 static int __devexit max7301_remove(struct spi_device *spi)
  80 {
  81         return __max730x_remove(&spi->dev);
  82 }
  83
  84 static const struct spi_device_id max7301_id[] = {
  85         { "max7301", 0 },
  86         { }
  87 };
  88 MODULE_DEVICE_TABLE(spi, max7301_id);
  89
  90 static struct spi_driver max7301_driver = {
  91         .driver = {
  92                 .name = "max7301",
  93                 .owner = THIS_MODULE,
  94         },
  95         .probe = max7301_probe,
  96         .remove = __devexit_p(max7301_remove),
  97         .id_table = max7301_id,
  98 };
  99
 100 static int __init max7301_init(void)
 101 {
 102         return spi_register_driver(&max7301_driver);
 103 }
 104 /* register after spi postcore initcall and before
 105  * subsys initcalls that may rely on these GPIOs
 106  */
 107 subsys_initcall(max7301_init);
 108
 109 static void __exit max7301_exit(void)
 110 {
 111         spi_unregister_driver(&max7301_driver);
 112 }
 113 module_exit(max7301_exit);
 114
 115 MODULE_AUTHOR("Juergen Beisert, Wolfram Sang");
 116 MODULE_LICENSE("GPL v2");
 117 MODULE_DESCRIPTION("MAX7301 GPIO-Expander");