1
2
3 modedb default video mode support
4
5
6 Currently all frame buffer device drivers have their own video mode databases,
7 which is a mess and a waste of resources. The main idea of modedb is to have
8
9 - one routine to probe for video modes, which can be used by all frame buffer
10 devices
11 - one generic video mode database with a fair amount of standard videomodes
12 (taken from XFree86)
13 - the possibility to supply your own mode database for graphics hardware that
14 needs non-standard modes, like amifb and Mac frame buffer drivers (which
15 use macmodes.c)
16
17 When a frame buffer device receives a video= option it doesn't know, it should
18 consider that to be a video mode option. If no frame buffer device is specified
19 in a video= option, fbmem considers that to be a global video mode option.
20
21 Valid mode specifiers (mode_option argument):
22
23 <xres>x<yres>[-<bpp>][@<refresh>]
24 <name>[-<bpp>][@<refresh>]
25
26 with <xres>, <yres>, <bpp> and <refresh> decimal numbers and <name> a string.
27 Things between square brackets are optional.
28
29 To find a suitable video mode, you just call
30
31 int __init fb_find_mode(struct fb_var_screeninfo *var,
32 struct fb_info *info, const char *mode_option,
33 const struct fb_videomode *db, unsigned int dbsize,
34 const struct fb_videomode *default_mode,
35 unsigned int default_bpp)
36
37 with db/dbsize your non-standard video mode database, or NULL to use the
38 standard video mode database.
39
40 fb_find_mode() first tries the specified video mode (or any mode that matches,
41 e.g. there can be multiple 640x480 modes, each of them is tried). If that
42 fails, the default mode is tried. If that fails, it walks over all modes.
43
44 To specify a video mode at bootup, use the following boot options:
45 video=<driver>:<xres>x<yres>[-<bpp>][@refresh]
46
47 where <driver> is a name from the table below. Valid default modes can be
48 found in linux/drivers/video/modedb.c. Check your driver's documentation.
49 There may be more modes.
50
51 Drivers that support modedb boot options
52 Boot Name Cards Supported
53
54 ami - Amiga chipset frame buffer
55 aty128fb - ATI Rage128 / Pro frame buffer
56 atyfb - ATI Mach64 frame buffer
57 tdfx - 3D Fx frame buffer
58
59 BTW, only a few drivers use this at the moment. Others are to follow
60 (feel free to send patches).
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