1 =================================
2 modedb default video mode support
3 =================================
4
5
6 Currently all frame buffer device drivers have
7 which is a mess and a waste of resources. The
8
9 - one routine to probe for video modes, whic
10 devices
11 - one generic video mode database with a fai
12 (taken from XFree86)
13 - the possibility to supply your own mode da
14 needs non-standard modes, like amifb and M
15 use macmodes.c)
16
17 When a frame buffer device receives a video= o
18 consider that to be a video mode option. If no
19 in a video= option, fbmem considers that to be
20
21 Valid mode specifiers (mode_option argument)::
22
23 <xres>x<yres>[M][R][-<bpp>][@<refresh>][i][
24 <name>[-<bpp>][@<refresh>]
25
26 with <xres>, <yres>, <bpp> and <refresh> decim
27 Things between square brackets are optional.
28
29 Valid names are::
30
31 - NSTC: 480i output, with the CCIR System-M
32 - NTSC-J: 480i output, with the CCIR System-
33 encoding, and a black level equal to the b
34 - PAL: 576i output, with the CCIR System-B T
35 - PAL-M: 480i output, with the CCIR System-M
36
37 If 'M' is specified in the mode_option argumen
38 <bpp> and <refresh>, if specified) the timings
39 VESA(TM) Coordinated Video Timings instead of
40 If 'R' is specified, do a 'reduced blanking' c
41 If 'i' is specified, calculate for an interlac
42 specified, add margins to the calculation (1.8
43 pixels and 1.8% of yres).
44
45 Sample usage: 1024x768M@60m - CVT timin
46
47 DRM drivers also add options to enable or disa
48
49 'e' will force the display to be enabled, i.e.
50 if a display is connected. 'D' will force the
51 digital output. This is useful for outputs tha
52 signals (e.g. HDMI and DVI-I). For other outpu
53 is specified the output is disabled.
54
55 You can additionally specify which output the
56 To force the VGA output to be enabled and driv
57
58 video=VGA-1:1280x1024@60me
59
60 Specifying the option multiple times for diffe
61
62 video=LVDS-1:d video=HDMI-1:D
63
64 Options can also be passed after the mode, usi
65
66 Sample usage: 720x480,rotate=180 - 720x
67
68 Valid options are::
69
70 - margin_top, margin_bottom, margin_left, ma
71 Number of pixels in the margins, typically
72 - reflect_x (boolean): Perform an axial symm
73 - reflect_y (boolean): Perform an axial symm
74 - rotate (integer): Rotate the initial frame
75 degrees. Valid values are 0, 90, 180 and 2
76 - tv_mode: Analog TV mode. One of "NTSC", "N
77 "PAL-M", "PAL-N", or "SECAM".
78 - panel_orientation, one of "normal", "upsid
79 "right_side_up". For KMS drivers only, thi
80 property on the kms connector as hint for
81
82
83 ----------------------------------------------
84
85 What is the VESA(TM) Coordinated Video Timings
86 ==============================================
87
88 From the VESA(TM) Website:
89
90 "The purpose of CVT is to provide a metho
91 and coordinated set of standard formats,
92 timing specifications for computer displ
93 employing CRTs, and those using other di
94 intention of CVT is to give both source
95 common set of tools to enable new timing
96 consistent manner that ensures greater c
97
98 This is the third standard approved by VESA(TM
99 first was the Discrete Video Timings (DVT) whi
100 pre-defined modes approved by VESA(TM). The s
101 Formula (GTF) which is an algorithm to calcula
102 pixelclock, the horizontal sync frequency, or
103
104 The GTF is limited by the fact that it is desi
105 It artificially increases the pixelclock becau
106 requirement. This is inappropriate for digital
107 data rate which requires that it conserves the
108 Also, GTF does not take into account the aspec
109
110 The CVT addresses these limitations. If used
111 is a derivation of GTF with a few modification
112 displays, the "reduced blanking" calculation c
113
114 From the framebuffer subsystem perspective, ne
115 to the global mode database whenever a new mod
116 manufacturers. Specifying for CVT will work fo
117 new CRT displays and probably with most flatpa
118 calculation is specified. (The CVT compatibil
119 determined from its EDID. The version 1.3 of t
120 blocks where additional timing information is
121 is no support yet in the layer to parse this a
122
123 CVT also introduced a new naming convention (s
124
125 <pix>M<a>[-R]
126
127 where: pix = total amount of pixels in MB
128 M = always present
129 a = aspect ratio (3 - 4:3; 4 - 5:
130 -R = reduced blanking
131
132 example: .48M3-R - 800x600 with red
133
134 Note: VESA(TM) has restrictions on what is a s
135
136 - aspect ratio can only be one of the ab
137 - acceptable refresh rates are 50, 60, 7
138 - if reduced blanking, the refresh rate
139
140 If one of the above are not satisfied, the ker
141 timings will still be calculated.
142
143 ----------------------------------------------
144
145 To find a suitable video mode, you just call::
146
147 int __init fb_find_mode(struct fb_var_screen
148 struct fb_info *info
149 const struct fb_vide
150 const struct fb_vide
151 unsigned int default
152
153 with db/dbsize your non-standard video mode da
154 standard video mode database.
155
156 fb_find_mode() first tries the specified video
157 e.g. there can be multiple 640x480 modes, each
158 fails, the default mode is tried. If that fail
159
160 To specify a video mode at bootup, use the fol
161
162 video=<driver>:<xres>x<yres>[-<bpp>][@refr
163
164 where <driver> is a name from the table below.
165 found in drivers/video/fbdev/core/modedb.c. C
166 There may be more modes::
167
168 Drivers that support modedb boot options
169 Boot Name Cards Supported
170
171 amifb - Amiga chipset frame buffer
172 aty128fb - ATI Rage128 / Pro frame buff
173 atyfb - ATI Mach64 frame buffer
174 pm2fb - Permedia 2/2V frame buffer
175 pm3fb - Permedia 3 frame buffer
176 sstfb - Voodoo 1/2 (SST1) chipset fr
177 tdfxfb - 3D Fx frame buffer
178 tridentfb - Trident (Cyber)blade chipset
179 vt8623fb - VIA 8623 frame buffer
180
181 BTW, only a few fb drivers use this at the mom
182 (feel free to send patches). The DRM drivers a
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