drivers/video/fbdev/core/fb_sys_fops.c

   1 /*
   2  * linux/drivers/video/fb_sys_read.c - Generic file operations where
   3  * framebuffer is in system RAM
   4  *
   5  * Copyright (C) 2007 Antonino Daplas <[email protected]>
   6  *
   7  * This file is subject to the terms and conditions of the GNU General Public
   8  * License.  See the file COPYING in the main directory of this archive
   9  * for more details.
  10  *
  11  */
  12 #include <linux/fb.h>
  13 #include <linux/module.h>
  14 #include <linux/uaccess.h>
  15
  16 ssize_t fb_sys_read(struct fb_info *info, char __user *buf, size_t count,
  17                     loff_t *ppos)
  18 {
  19         unsigned long p = *ppos;
  20         void *src;
  21         int err = 0;
  22         unsigned long total_size, c;
  23         ssize_t ret;
  24
  25         if (!info->screen_buffer)
  26                 return -ENODEV;
  27
  28         total_size = info->screen_size;
  29
  30         if (total_size == 0)
  31                 total_size = info->fix.smem_len;
  32
  33         if (p >= total_size)
  34                 return 0;
  35
  36         if (count >= total_size)
  37                 count = total_size;
  38
  39         if (count + p > total_size)
  40                 count = total_size - p;
  41
  42         src = info->screen_buffer + p;
  43
  44         if (info->fbops->fb_sync)
  45                 info->fbops->fb_sync(info);
  46
  47         c = copy_to_user(buf, src, count);
  48         if (c)
  49                 err = -EFAULT;
  50         ret = count - c;
  51
  52         *ppos += ret;
  53
  54         return ret ? ret : err;
  55 }
  56 EXPORT_SYMBOL_GPL(fb_sys_read);
  57
  58 ssize_t fb_sys_write(struct fb_info *info, const char __user *buf,
  59                      size_t count, loff_t *ppos)
  60 {
  61         unsigned long p = *ppos;
  62         void *dst;
  63         int err = 0;
  64         unsigned long total_size, c;
  65         size_t ret;
  66
  67         if (!info->screen_buffer)
  68                 return -ENODEV;
  69
  70         total_size = info->screen_size;
  71
  72         if (total_size == 0)
  73                 total_size = info->fix.smem_len;
  74
  75         if (p > total_size)
  76                 return -EFBIG;
  77
  78         if (count > total_size) {
  79                 err = -EFBIG;
  80                 count = total_size;
  81         }
  82
  83         if (count + p > total_size) {
  84                 if (!err)
  85                         err = -ENOSPC;
  86
  87                 count = total_size - p;
  88         }
  89
  90         dst = info->screen_buffer + p;
  91
  92         if (info->fbops->fb_sync)
  93                 info->fbops->fb_sync(info);
  94
  95         c = copy_from_user(dst, buf, count);
  96         if (c)
  97                 err = -EFAULT;
  98         ret = count - c;
  99
 100         *ppos += ret;
 101
 102         return ret ? ret : err;
 103 }
 104 EXPORT_SYMBOL_GPL(fb_sys_write);
 105
 106 MODULE_AUTHOR("Antonino Daplas <[email protected]>");
 107 MODULE_DESCRIPTION("Generic file read (fb in system RAM)");
 108 MODULE_LICENSE("GPL");