target/linux/generic/files-2.6.25/drivers/char/gpio_dev.c

   1 /*
   2  * character device wrapper for generic gpio layer
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA02111-1307USA
  17  *
  18  * Feedback, Bugs...  blogic@openwrt.org
  19  *
  20  */
  21
  22 #include <linux/module.h>
  23 #include <linux/errno.h>
  24 #include <linux/init.h>
  25 #include <asm/uaccess.h>
  26 #include <asm/io.h>
  27 #include <asm/gpio.h>
  28 #include <asm/atomic.h>
  29 #include <linux/init.h>
  30 #include <linux/genhd.h>
  31 #include <linux/device.h>
  32 #include <linux/platform_device.h>
  33 #include <linux/gpio_dev.h>
  34
  35 #define DRVNAME         "gpiodev"
  36 #define DEVNAME         "gpio"
  37
  38 static int dev_major;
  39 static unsigned int gpio_access_mask;
  40 static struct class *gpiodev_class;
  41
  42 /* Counter is 1, if the device is not opened and zero (or less) if opened. */
  43 static atomic_t gpio_open_cnt = ATOMIC_INIT(1);
  44
  45 static int
  46 gpio_ioctl(struct inode * inode, struct file * file, unsigned int cmd, unsigned long arg)
  47 {
  48         int retval = 0;
  49
  50         if (((1 << arg) & gpio_access_mask) != (1 << arg))
  51         {
  52                 retval = -EINVAL;
  53                 goto out;
  54         }
  55
  56         switch (cmd)
  57         {
  58         case GPIO_GET:
  59                 retval = gpio_get_value(arg);
  60                 break;
  61
  62         case GPIO_SET:
  63                 gpio_set_value(arg, 1);
  64                 break;
  65
  66         case GPIO_CLEAR:
  67                 gpio_set_value(arg, 0);
  68                 break;
  69
  70         case GPIO_DIR_IN:
  71                 gpio_direction_input(arg);
  72                 break;
  73
  74         case GPIO_DIR_OUT:
  75                 gpio_direction_output(arg, 0);
  76                 break;
  77
  78         default:
  79                 retval = -EINVAL;
  80                 break;
  81         }
  82
  83 out:
  84         return retval;
  85 }
  86
  87 static int
  88 gpio_open(struct inode *inode, struct file *file)
  89 {
  90         int result = 0;
  91         unsigned int dev_minor = MINOR(inode->i_rdev);
  92
  93         if (dev_minor != 0)
  94         {
  95                 printk(KERN_ERR DRVNAME ": trying to access unknown minor device -> %d\n", dev_minor);
  96                 result = -ENODEV;
  97                 goto out;
  98         }
  99
 100         /* FIXME: We should really allow multiple applications to open the device
 101          *        at the same time, as long as the apps access different IO pins.
 102          *        The generic gpio-registration functions can be used for that.
 103          *        Two new IOCTLs have to be introduced for that. Need to check userspace
 104          *        compatibility first. --mb */
 105         if (!atomic_dec_and_test(&gpio_open_cnt)) {
 106                 atomic_inc(&gpio_open_cnt);
 107                 printk(KERN_ERR DRVNAME ": Device with minor ID %d already in use\n", dev_minor);
 108                 result = -EBUSY;
 109                 goto out;
 110         }
 111
 112 out:
 113         return result;
 114 }
 115
 116 static int
 117 gpio_close(struct inode * inode, struct file * file)
 118 {
 119         smp_mb__before_atomic_inc();
 120         atomic_inc(&gpio_open_cnt);
 121
 122         return 0;
 123 }
 124
 125 struct file_operations gpio_fops = {
 126         ioctl:          gpio_ioctl,
 127         open:           gpio_open,
 128         release:        gpio_close
 129 };
 130
 131 static int
 132 gpio_probe(struct platform_device *dev)
 133 {
 134         int result = 0;
 135
 136         dev_major = register_chrdev(0, DEVNAME, &gpio_fops);
 137         if (!dev_major)
 138         {
 139                 printk(KERN_ERR DRVNAME ": Error whilst opening %s \n", DEVNAME);
 140                 result = -ENODEV;
 141                 goto out;
 142         }
 143
 144         gpiodev_class = class_create(THIS_MODULE, DRVNAME);
 145         class_device_create(gpiodev_class, NULL, MKDEV(dev_major, 0), NULL, DEVNAME);
 146
 147         printk(KERN_INFO DRVNAME ": gpio device registered with major %d\n", dev_major);
 148
 149         if (dev->num_resources != 1)
 150         {
 151                 printk(KERN_ERR DRVNAME ": device may only have 1 resource\n");
 152                 result = -ENODEV;
 153                 goto out;
 154         }
 155
 156         gpio_access_mask = dev->resource[0].start;
 157
 158         printk(KERN_INFO DRVNAME ": gpio platform device registered with access mask %08X\n", gpio_access_mask);
 159 out:
 160         return result;
 161 }
 162
 163 static int
 164 gpio_remove(struct platform_device *dev)
 165 {
 166         unregister_chrdev(dev_major, DEVNAME);
 167         return 0;
 168 }
 169
 170 static struct
 171 platform_driver gpio_driver = {
 172         .probe = gpio_probe,
 173         .remove = gpio_remove,
 174         .driver = {
 175                 .name = "GPIODEV",
 176                 .owner = THIS_MODULE,
 177         },
 178 };
 179
 180 static int __init
 181 gpio_mod_init(void)
 182 {
 183         int ret = platform_driver_register(&gpio_driver);
 184         if (ret)
 185                 printk(KERN_INFO DRVNAME ": Error registering platfom driver!");
 186
 187         return ret;
 188 }
 189
 190 static void __exit
 191 gpio_mod_exit(void)
 192 {
 193         platform_driver_unregister(&gpio_driver);
 194 }
 195
 196 module_init (gpio_mod_init);
 197 module_exit (gpio_mod_exit);
 198
 199 MODULE_LICENSE("GPL");
 200 MODULE_AUTHOR("John Crispin / OpenWrt");
 201 MODULE_DESCRIPTION("Character device for for generic gpio api");