kernel/drivers/staging/speakup/devsynth.c

   1 #include <linux/errno.h>
   2 #include <linux/miscdevice.h>   /* for misc_register, and SYNTH_MINOR */
   3 #include <linux/types.h>
   4 #include <linux/uaccess.h>
   5
   6 #include "speakup.h"
   7 #include "spk_priv.h"
   8
   9 #ifndef SYNTH_MINOR
  10 #define SYNTH_MINOR 25
  11 #endif
  12
  13 static int misc_registered;
  14 static int dev_opened;
  15
  16 static ssize_t speakup_file_write(struct file *fp, const char __user *buffer,
  17                                   size_t nbytes, loff_t *ppos)
  18 {
  19         size_t count = nbytes;
  20         const char __user *ptr = buffer;
  21         size_t bytes;
  22         unsigned long flags;
  23         u_char buf[256];
  24
  25         if (synth == NULL)
  26                 return -ENODEV;
  27         while (count > 0) {
  28                 bytes = min(count, sizeof(buf));
  29                 if (copy_from_user(buf, ptr, bytes))
  30                         return -EFAULT;
  31                 count -= bytes;
  32                 ptr += bytes;
  33                 spin_lock_irqsave(&speakup_info.spinlock, flags);
  34                 synth_write(buf, bytes);
  35                 spin_unlock_irqrestore(&speakup_info.spinlock, flags);
  36         }
  37         return (ssize_t) nbytes;
  38 }
  39
  40 static ssize_t speakup_file_read(struct file *fp, char __user *buf,
  41                                  size_t nbytes, loff_t *ppos)
  42 {
  43         return 0;
  44 }
  45
  46 static int speakup_file_open(struct inode *ip, struct file *fp)
  47 {
  48         if (synth == NULL)
  49                 return -ENODEV;
  50         if (xchg(&dev_opened, 1))
  51                 return -EBUSY;
  52         return 0;
  53 }
  54
  55 static int speakup_file_release(struct inode *ip, struct file *fp)
  56 {
  57         dev_opened = 0;
  58         return 0;
  59 }
  60
  61 static const struct file_operations synth_fops = {
  62         .read = speakup_file_read,
  63         .write = speakup_file_write,
  64         .open = speakup_file_open,
  65         .release = speakup_file_release,
  66 };
  67
  68 static struct miscdevice synth_device = {
  69         .minor = SYNTH_MINOR,
  70         .name = "synth",
  71         .fops = &synth_fops,
  72 };
  73
  74 void speakup_register_devsynth(void)
  75 {
  76         if (misc_registered != 0)
  77                 return;
  78 /* zero it so if register fails, deregister will not ref invalid ptrs */
  79         if (misc_register(&synth_device))
  80                 pr_warn("Couldn't initialize miscdevice /dev/synth.\n");
  81         else {
  82                 pr_info("initialized device: /dev/synth, node (MAJOR %d, MINOR %d)\n",
  83                         MISC_MAJOR, SYNTH_MINOR);
  84                 misc_registered = 1;
  85         }
  86 }
  87
  88 void speakup_unregister_devsynth(void)
  89 {
  90         if (!misc_registered)
  91                 return;
  92         pr_info("speakup: unregistering synth device /dev/synth\n");
  93         misc_deregister(&synth_device);
  94         misc_registered = 0;
  95 }