drivers/char/scx200_gpio.c

   1 /* linux/drivers/char/scx200_gpio.c
   2
   3    National Semiconductor SCx200 GPIO driver.  Allows a user space
   4    process to play with the GPIO pins.
   5
   6    Copyright (c) 2001,2002 Christer Weinigel <wingel@nano-system.com> */
   7
   8 #include <linux/config.h>
   9 #include <linux/fs.h>
  10 #include <linux/module.h>
  11 #include <linux/errno.h>
  12 #include <linux/kernel.h>
  13 #include <linux/init.h>
  14 #include <asm/uaccess.h>
  15 #include <asm/io.h>
  16
  17 #include <linux/scx200_gpio.h>
  18
  19 #define NAME "scx200_gpio"
  20
  21 MODULE_AUTHOR("Christer Weinigel <wingel@nano-system.com>");
  22 MODULE_DESCRIPTION("NatSemi SCx200 GPIO Pin Driver");
  23 MODULE_LICENSE("GPL");
  24
  25 static int major = 0;           /* default to dynamic major */
  26 module_param(major, int, 0);
  27 MODULE_PARM_DESC(major, "Major device number");
  28
  29 static ssize_t scx200_gpio_write(struct file *file, const char __user *data,
  30                                  size_t len, loff_t *ppos)
  31 {
  32         unsigned m = iminor(file->f_dentry->d_inode);
  33         size_t i;
  34
  35         for (i = 0; i < len; ++i) {
  36                 char c;
  37                 if (get_user(c, data+i))
  38                         return -EFAULT;
  39                 switch (c)
  40                 {
  41                 case '0':
  42                         scx200_gpio_set(m, 0);
  43                         break;
  44                 case '1':
  45                         scx200_gpio_set(m, 1);
  46                         break;
  47                 case 'O':
  48                         printk(KERN_INFO NAME ": GPIO%d output enabled\n", m);
  49                         scx200_gpio_configure(m, ~1, 1);
  50                         break;
  51                 case 'o':
  52                         printk(KERN_INFO NAME ": GPIO%d output disabled\n", m);
  53                         scx200_gpio_configure(m, ~1, 0);
  54                         break;
  55                 case 'T':
  56                         printk(KERN_INFO NAME ": GPIO%d output is push pull\n", m);
  57                         scx200_gpio_configure(m, ~2, 2);
  58                         break;
  59                 case 't':
  60                         printk(KERN_INFO NAME ": GPIO%d output is open drain\n", m);
  61                         scx200_gpio_configure(m, ~2, 0);
  62                         break;
  63                 case 'P':
  64                         printk(KERN_INFO NAME ": GPIO%d pull up enabled\n", m);
  65                         scx200_gpio_configure(m, ~4, 4);
  66                         break;
  67                 case 'p':
  68                         printk(KERN_INFO NAME ": GPIO%d pull up disabled\n", m);
  69                         scx200_gpio_configure(m, ~4, 0);
  70                         break;
  71                 }
  72         }
  73
  74         return len;
  75 }
  76
  77 static ssize_t scx200_gpio_read(struct file *file, char __user *buf,
  78                                 size_t len, loff_t *ppos)
  79 {
  80         unsigned m = iminor(file->f_dentry->d_inode);
  81         int value;
  82
  83         value = scx200_gpio_get(m);
  84         if (put_user(value ? '1' : '0', buf))
  85                 return -EFAULT;
  86
  87         return 1;
  88 }
  89
  90 static int scx200_gpio_open(struct inode *inode, struct file *file)
  91 {
  92         unsigned m = iminor(inode);
  93         if (m > 63)
  94                 return -EINVAL;
  95         return nonseekable_open(inode, file);
  96 }
  97
  98 static int scx200_gpio_release(struct inode *inode, struct file *file)
  99 {
 100         return 0;
 101 }
 102
 103
 104 static struct file_operations scx200_gpio_fops = {
 105         .owner   = THIS_MODULE,
 106         .write   = scx200_gpio_write,
 107         .read    = scx200_gpio_read,
 108         .open    = scx200_gpio_open,
 109         .release = scx200_gpio_release,
 110 };
 111
 112 static int __init scx200_gpio_init(void)
 113 {
 114         int r;
 115
 116         printk(KERN_DEBUG NAME ": NatSemi SCx200 GPIO Driver\n");
 117
 118         if (!scx200_gpio_present()) {
 119                 printk(KERN_ERR NAME ": no SCx200 gpio pins available\n");
 120                 return -ENODEV;
 121         }
 122
 123         r = register_chrdev(major, NAME, &scx200_gpio_fops);
 124         if (r < 0) {
 125                 printk(KERN_ERR NAME ": unable to register character device\n");
 126                 return r;
 127         }
 128         if (!major) {
 129                 major = r;
 130                 printk(KERN_DEBUG NAME ": got dynamic major %d\n", major);
 131         }
 132
 133         return 0;
 134 }
 135
 136 static void __exit scx200_gpio_cleanup(void)
 137 {
 138         unregister_chrdev(major, NAME);
 139 }
 140
 141 module_init(scx200_gpio_init);
 142 module_exit(scx200_gpio_cleanup);
 143
 144 /*
 145     Local variables:
 146         compile-command: "make -k -C ../.. SUBDIRS=drivers/char modules"
 147         c-basic-offset: 8
 148     End:
 149 */