1 ===============
2 What is vesafb?
3 ===============
4
5 This is a generic driver for a graphic framebu
6
7 The idea is simple: Turn on graphics mode at
8 of the BIOS, and use this as framebuffer devic
9 (and other) ports do.
10
11 This means we decide at boot time whenever we
12 graphics mode. Switching mode later on (in pr
13 impossible; BIOS calls work in real mode only.
14 Version 2.0 are required, because we need a li
15
16 Advantages:
17
18 * It provides a nice large console (128 cols
19 without using tiny, unreadable fonts.
20 * You can run XF68_FBDev on top of /dev/fb0 (
21 support for every VBE 2.0 compliant graphic
22 * Most important: boot logo :-)
23
24 Disadvantages:
25
26 * graphic mode is slower than text mode...
27
28
29 How to use it?
30 ==============
31
32 Switching modes is done using the vga=... boot
33 Documentation/admin-guide/svga.rst for details
34
35 You should compile in both vgacon (for text mo
36 graphics mode). Which of them takes over the c
37 whenever the specified mode is text or graphic
38
39 The graphic modes are NOT in the list which yo
40 vga=ask and hit return. The mode you wish to u
41 VESA mode number. Here are those VESA mode num
42
43 ====== ======= ======= ======== =========
44 colors 640x480 800x600 1024x768 1280x1024
45 ====== ======= ======= ======== =========
46 256 0x101 0x103 0x105 0x107
47 32k 0x110 0x113 0x116 0x119
48 64k 0x111 0x114 0x117 0x11A
49 16M 0x112 0x115 0x118 0x11B
50 ====== ======= ======= ======== =========
51
52
53 The video mode number of the Linux kernel is t
54 0x200:
55
56 Linux_kernel_mode_number = VESA_mode_number +
57
58 So the table for the Kernel mode numbers are:
59
60 ====== ======= ======= ======== =========
61 colors 640x480 800x600 1024x768 1280x1024
62 ====== ======= ======= ======== =========
63 256 0x301 0x303 0x305 0x307
64 32k 0x310 0x313 0x316 0x319
65 64k 0x311 0x314 0x317 0x31A
66 16M 0x312 0x315 0x318 0x31B
67 ====== ======= ======= ======== =========
68
69 To enable one of those modes you have to speci
70 lilo.conf file and rerun LILO. Then you can ty
71 mode at the "vga=ask" prompt. For example if y
72 1024x768x256 colors you have to say "305" at t
73
74 If this does not work, this might be because y
75 linear framebuffers or because it does not sup
76 Even if your board does, it might be the BIOS
77 Extensions v2.0 are required, 1.2 is NOT suffi
78 "bad mode number" message if something goes wr
79
80 1. Note: LILO cannot handle hex, for booting d
81 "vga=mode-number" you have to transform the
82 2. Note: Some newer versions of LILO appear to
83 if you set the 0x in front of the numbers.
84
85 X11
86 ===
87
88 XF68_FBDev should work just fine, but it is no
89 another (accelerated) X-Server like XF86_SVGA
90 It depends on X-Server and graphics board.
91
92 The X-Server must restore the video mode corre
93 with a broken console (and vesafb cannot do an
94
95
96 Refresh rates
97 =============
98
99 There is no way to change the vesafb video mod
100 booting linux. If you are not happy with the
101 have these options:
102
103 * configure and load the DOS-Tools for the gr
104 available) and boot linux with loadlin.
105 * use a native driver (matroxfb/atyfb) instea
106 is available, write a new one!
107 * VBE 3.0 might work too. I have neither a g
108 support nor the specs, so I have not checke
109
110
111 Configuration
112 =============
113
114 The VESA BIOS provides protected mode interfac
115 some parameters. vesafb can use it for palett
116 to pan the display. It is turned off by defau
117 seems not to work with some BIOS versions, but
118 to turn it on.
119
120 You can pass options to vesafb using "video=ve
121 the kernel command line. Multiple options sho
122 by comma, like this: "video=vesafb:ypan,invers
123
124 Accepted options:
125
126 inverse use inverse color map
127
128 ========= ====================================
129 ypan enable display panning using the VES
130 interface. The visible screen is ju
131 video memory, console scrolling is d
132 start of the window.
133
134 pro:
135
136 * scrolling (fullscreen) is fa
137 no need to copy around data.
138
139 kontra:
140
141 * scrolling only parts of the
142 ugly flicker effects (boot l
143 example).
144
145 ywrap Same as ypan, but assumes your gfx b
146 the video memory (i.e. starts readin
147 reaches the end of video memory). F
148
149 redraw Scroll by redrawing the affected par
150 is the safe (and slow) default.
151
152
153 vgapal Use the standard vga registers for p
154 This is the default.
155 pmipal Use the protected mode interface for
156
157 mtrr:n Setup memory type range registers fo
158 where n:
159
160 - 0 - disabled (equivalent to no
161 - 1 - uncachable
162 - 2 - write-back
163 - 3 - write-combining
164 - 4 - write-through
165
166 If you see the following in dmesg, c
167 old one. In this example, use "mtrr:
168 ...
169 mtrr: type mismatch for e0000000,8000000 o
170 write-combining
171 ...
172
173 nomtrr disable mtrr
174
175 vremap:n
176 Remap 'n' MiB of video RAM. If 0 or
177 according to video mode. (2.5.66 pat
178 reversed to give override possibilit
179 than the kernel would) to 2.4 by tmb
180
181 vtotal:n If the video BIOS of your card incor
182 amount of video RAM, use this option
183 ========= ====================================
184
185 Have fun!
186
187 Gerd Knorr <kraxel@goldbach.in-berlin.de>
188
189 Minor (mostly typo) changes
190 by Nico Schmoigl <schmoigl@rumms.uni-mannheim.d
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