drivers/gpio/gpio-max7301.c

   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 */
  22 static 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
  33 static 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
  53 static 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         if (spi->dev.platform_data)
  60                 spi->bits_per_word = 16;
  61         ret = spi_setup(spi);
  62         if (ret < 0)
  63                 return ret;
  64
  65         ts = devm_kzalloc(&spi->dev, 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         return ret;
  75 }
  76
  77 static int max7301_remove(struct spi_device *spi)
  78 {
  79         return __max730x_remove(&spi->dev);
  80 }
  81
  82 static const struct spi_device_id max7301_id[] = {
  83         { "max7301", 0 },
  84         { }
  85 };
  86 MODULE_DEVICE_TABLE(spi, max7301_id);
  87
  88 static struct spi_driver max7301_driver = {
  89         .driver = {
  90                 .name = "max7301",
  91                 .owner = THIS_MODULE,
  92         },
  93         .probe = max7301_probe,
  94         .remove = max7301_remove,
  95         .id_table = max7301_id,
  96 };
  97
  98 static int __init max7301_init(void)
  99 {
 100         return spi_register_driver(&max7301_driver);
 101 }
 102 /* register after spi postcore initcall and before
 103  * subsys initcalls that may rely on these GPIOs
 104  */
 105 subsys_initcall(max7301_init);
 106
 107 static void __exit max7301_exit(void)
 108 {
 109         spi_unregister_driver(&max7301_driver);
 110 }
 111 module_exit(max7301_exit);
 112
 113 MODULE_AUTHOR("Juergen Beisert, Wolfram Sang");
 114 MODULE_LICENSE("GPL v2");
 115 MODULE_DESCRIPTION("MAX7301 GPIO-Expander");