xref: /linux/drivers/video/fbdev/core/fb_sys_fops.c (revision 0ea5c948cb64bab5bc7a5516774eb8536f05aa0d)
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 <adaplas@pol.net>
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 
fb_sys_read(struct fb_info * info,char __user * buf,size_t count,loff_t * ppos)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->flags & FBINFO_VIRTFB))
26 		fb_warn_once(info, "Framebuffer is not in virtual address space.");
27 
28 	if (!info->screen_buffer)
29 		return -ENODEV;
30 
31 	total_size = info->screen_size;
32 
33 	if (total_size == 0)
34 		total_size = info->fix.smem_len;
35 
36 	if (p >= total_size)
37 		return 0;
38 
39 	if (count >= total_size)
40 		count = total_size;
41 
42 	if (count + p > total_size)
43 		count = total_size - p;
44 
45 	src = info->screen_buffer + p;
46 
47 	if (info->fbops->fb_sync)
48 		info->fbops->fb_sync(info);
49 
50 	c = copy_to_user(buf, src, count);
51 	if (c)
52 		err = -EFAULT;
53 	ret = count - c;
54 
55 	*ppos += ret;
56 
57 	return ret ? ret : err;
58 }
59 EXPORT_SYMBOL_GPL(fb_sys_read);
60 
fb_sys_write(struct fb_info * info,const char __user * buf,size_t count,loff_t * ppos)61 ssize_t fb_sys_write(struct fb_info *info, const char __user *buf,
62 		     size_t count, loff_t *ppos)
63 {
64 	unsigned long p = *ppos;
65 	void *dst;
66 	int err = 0;
67 	unsigned long total_size, c;
68 	size_t ret;
69 
70 	if (!(info->flags & FBINFO_VIRTFB))
71 		fb_warn_once(info, "Framebuffer is not in virtual address space.");
72 
73 	if (!info->screen_buffer)
74 		return -ENODEV;
75 
76 	total_size = info->screen_size;
77 
78 	if (total_size == 0)
79 		total_size = info->fix.smem_len;
80 
81 	if (p > total_size)
82 		return -EFBIG;
83 
84 	if (count > total_size) {
85 		err = -EFBIG;
86 		count = total_size;
87 	}
88 
89 	if (count + p > total_size) {
90 		if (!err)
91 			err = -ENOSPC;
92 
93 		count = total_size - p;
94 	}
95 
96 	dst = info->screen_buffer + p;
97 
98 	if (info->fbops->fb_sync)
99 		info->fbops->fb_sync(info);
100 
101 	c = copy_from_user(dst, buf, count);
102 	if (c)
103 		err = -EFAULT;
104 	ret = count - c;
105 
106 	*ppos += ret;
107 
108 	return ret ? ret : err;
109 }
110 EXPORT_SYMBOL_GPL(fb_sys_write);
111 
112 MODULE_AUTHOR("Antonino Daplas <adaplas@pol.net>");
113 MODULE_DESCRIPTION("Generic file read (fb in system RAM)");
114 MODULE_LICENSE("GPL");
115