Contents of /alx-src/tags/kernel26-2.6.12-alx-r9/Documentation/svga.txt
Parent Directory | Revision Log
Revision 630 -
(show annotations)
(download)
Wed Mar 4 11:03:09 2009 UTC (15 years, 6 months ago) by niro
File MIME type: text/plain
File size: 14402 byte(s)
Wed Mar 4 11:03:09 2009 UTC (15 years, 6 months ago) by niro
File MIME type: text/plain
File size: 14402 byte(s)
Tag kernel26-2.6.12-alx-r9
1 | Video Mode Selection Support 2.13 |
2 | (c) 1995--1999 Martin Mares, <mj@ucw.cz> |
3 | -------------------------------------------------------------------------------- |
4 | |
5 | 1. Intro |
6 | ~~~~~~~~ |
7 | This small document describes the "Video Mode Selection" feature which |
8 | allows the use of various special video modes supported by the video BIOS. Due |
9 | to usage of the BIOS, the selection is limited to boot time (before the |
10 | kernel decompression starts) and works only on 80X86 machines. |
11 | |
12 | ** Short intro for the impatient: Just use vga=ask for the first time, |
13 | ** enter `scan' on the video mode prompt, pick the mode you want to use, |
14 | ** remember its mode ID (the four-digit hexadecimal number) and then |
15 | ** set the vga parameter to this number (converted to decimal first). |
16 | |
17 | The video mode to be used is selected by a kernel parameter which can be |
18 | specified in the kernel Makefile (the SVGA_MODE=... line) or by the "vga=..." |
19 | option of LILO (or some other boot loader you use) or by the "vidmode" utility |
20 | (present in standard Linux utility packages). You can use the following values |
21 | of this parameter: |
22 | |
23 | NORMAL_VGA - Standard 80x25 mode available on all display adapters. |
24 | |
25 | EXTENDED_VGA - Standard 8-pixel font mode: 80x43 on EGA, 80x50 on VGA. |
26 | |
27 | ASK_VGA - Display a video mode menu upon startup (see below). |
28 | |
29 | 0..35 - Menu item number (when you have used the menu to view the list of |
30 | modes available on your adapter, you can specify the menu item you want |
31 | to use). 0..9 correspond to "0".."9", 10..35 to "a".."z". Warning: the |
32 | mode list displayed may vary as the kernel version changes, because the |
33 | modes are listed in a "first detected -- first displayed" manner. It's |
34 | better to use absolute mode numbers instead. |
35 | |
36 | 0x.... - Hexadecimal video mode ID (also displayed on the menu, see below |
37 | for exact meaning of the ID). Warning: rdev and LILO don't support |
38 | hexadecimal numbers -- you have to convert it to decimal manually. |
39 | |
40 | 2. Menu |
41 | ~~~~~~~ |
42 | The ASK_VGA mode causes the kernel to offer a video mode menu upon |
43 | bootup. It displays a "Press <RETURN> to see video modes available, <SPACE> |
44 | to continue or wait 30 secs" message. If you press <RETURN>, you enter the |
45 | menu, if you press <SPACE> or wait 30 seconds, the kernel will boot up in |
46 | the standard 80x25 mode. |
47 | |
48 | The menu looks like: |
49 | |
50 | Video adapter: <name-of-detected-video-adapter> |
51 | Mode: COLSxROWS: |
52 | 0 0F00 80x25 |
53 | 1 0F01 80x50 |
54 | 2 0F02 80x43 |
55 | 3 0F03 80x26 |
56 | .... |
57 | Enter mode number or `scan': <flashing-cursor-here> |
58 | |
59 | <name-of-detected-video-adapter> tells what video adapter did Linux detect |
60 | -- it's either a generic adapter name (MDA, CGA, HGC, EGA, VGA, VESA VGA [a VGA |
61 | with VESA-compliant BIOS]) or a chipset name (e.g., Trident). Direct detection |
62 | of chipsets is turned off by default (see CONFIG_VIDEO_SVGA in chapter 4 to see |
63 | how to enable it if you really want) as it's inherently unreliable due to |
64 | absolutely insane PC design. |
65 | |
66 | "0 0F00 80x25" means that the first menu item (the menu items are numbered |
67 | from "0" to "9" and from "a" to "z") is a 80x25 mode with ID=0x0f00 (see the |
68 | next section for a description of mode IDs). |
69 | |
70 | <flashing-cursor-here> encourages you to enter the item number or mode ID |
71 | you wish to set and press <RETURN>. If the computer complains something about |
72 | "Unknown mode ID", it is trying to tell you that it isn't possible to set such |
73 | a mode. It's also possible to press only <RETURN> which leaves the current mode. |
74 | |
75 | The mode list usually contains a few basic modes and some VESA modes. In |
76 | case your chipset has been detected, some chipset-specific modes are shown as |
77 | well (some of these might be missing or unusable on your machine as different |
78 | BIOSes are often shipped with the same card and the mode numbers depend purely |
79 | on the VGA BIOS). |
80 | |
81 | The modes displayed on the menu are partially sorted: The list starts with |
82 | the standard modes (80x25 and 80x50) followed by "special" modes (80x28 and |
83 | 80x43), local modes (if the local modes feature is enabled), VESA modes and |
84 | finally SVGA modes for the auto-detected adapter. |
85 | |
86 | If you are not happy with the mode list offered (e.g., if you think your card |
87 | is able to do more), you can enter "scan" instead of item number / mode ID. The |
88 | program will try to ask the BIOS for all possible video mode numbers and test |
89 | what happens then. The screen will be probably flashing wildly for some time and |
90 | strange noises will be heard from inside the monitor and so on and then, really |
91 | all consistent video modes supported by your BIOS will appear (plus maybe some |
92 | `ghost modes'). If you are afraid this could damage your monitor, don't use this |
93 | function. |
94 | |
95 | After scanning, the mode ordering is a bit different: the auto-detected SVGA |
96 | modes are not listed at all and the modes revealed by `scan' are shown before |
97 | all VESA modes. |
98 | |
99 | 3. Mode IDs |
100 | ~~~~~~~~~~~ |
101 | Because of the complexity of all the video stuff, the video mode IDs |
102 | used here are also a bit complex. A video mode ID is a 16-bit number usually |
103 | expressed in a hexadecimal notation (starting with "0x"). You can set a mode |
104 | by entering its mode directly if you know it even if it isn't shown on the menu. |
105 | |
106 | The ID numbers can be divided to three regions: |
107 | |
108 | 0x0000 to 0x00ff - menu item references. 0x0000 is the first item. Don't use |
109 | outside the menu as this can change from boot to boot (especially if you |
110 | have used the `scan' feature). |
111 | |
112 | 0x0100 to 0x017f - standard BIOS modes. The ID is a BIOS video mode number |
113 | (as presented to INT 10, function 00) increased by 0x0100. |
114 | |
115 | 0x0200 to 0x08ff - VESA BIOS modes. The ID is a VESA mode ID increased by |
116 | 0x0100. All VESA modes should be autodetected and shown on the menu. |
117 | |
118 | 0x0900 to 0x09ff - Video7 special modes. Set by calling INT 0x10, AX=0x6f05. |
119 | (Usually 940=80x43, 941=132x25, 942=132x44, 943=80x60, 944=100x60, |
120 | 945=132x28 for the standard Video7 BIOS) |
121 | |
122 | 0x0f00 to 0x0fff - special modes (they are set by various tricks -- usually |
123 | by modifying one of the standard modes). Currently available: |
124 | 0x0f00 standard 80x25, don't reset mode if already set (=FFFF) |
125 | 0x0f01 standard with 8-point font: 80x43 on EGA, 80x50 on VGA |
126 | 0x0f02 VGA 80x43 (VGA switched to 350 scanlines with a 8-point font) |
127 | 0x0f03 VGA 80x28 (standard VGA scans, but 14-point font) |
128 | 0x0f04 leave current video mode |
129 | 0x0f05 VGA 80x30 (480 scans, 16-point font) |
130 | 0x0f06 VGA 80x34 (480 scans, 14-point font) |
131 | 0x0f07 VGA 80x60 (480 scans, 8-point font) |
132 | 0x0f08 Graphics hack (see the CONFIG_VIDEO_HACK paragraph below) |
133 | |
134 | 0x1000 to 0x7fff - modes specified by resolution. The code has a "0xRRCC" |
135 | form where RR is a number of rows and CC is a number of columns. |
136 | E.g., 0x1950 corresponds to a 80x25 mode, 0x2b84 to 132x43 etc. |
137 | This is the only fully portable way to refer to a non-standard mode, |
138 | but it relies on the mode being found and displayed on the menu |
139 | (remember that mode scanning is not done automatically). |
140 | |
141 | 0xff00 to 0xffff - aliases for backward compatibility: |
142 | 0xffff equivalent to 0x0f00 (standard 80x25) |
143 | 0xfffe equivalent to 0x0f01 (EGA 80x43 or VGA 80x50) |
144 | |
145 | If you add 0x8000 to the mode ID, the program will try to recalculate |
146 | vertical display timing according to mode parameters, which can be used to |
147 | eliminate some annoying bugs of certain VGA BIOSes (usually those used for |
148 | cards with S3 chipsets and old Cirrus Logic BIOSes) -- mainly extra lines at the |
149 | end of the display. |
150 | |
151 | 4. Options |
152 | ~~~~~~~~~~ |
153 | Some options can be set in the source text (in arch/i386/boot/video.S). |
154 | All of them are simple #define's -- change them to #undef's when you want to |
155 | switch them off. Currently supported: |
156 | |
157 | CONFIG_VIDEO_SVGA - enables autodetection of SVGA cards. This is switched |
158 | off by default as it's a bit unreliable due to terribly bad PC design. If you |
159 | really want to have the adapter autodetected (maybe in case the `scan' feature |
160 | doesn't work on your machine), switch this on and don't cry if the results |
161 | are not completely sane. In case you really need this feature, please drop me |
162 | a mail as I think of removing it some day. |
163 | |
164 | CONFIG_VIDEO_VESA - enables autodetection of VESA modes. If it doesn't work |
165 | on your machine (or displays a "Error: Scanning of VESA modes failed" message), |
166 | you can switch it off and report as a bug. |
167 | |
168 | CONFIG_VIDEO_COMPACT - enables compacting of the video mode list. If there |
169 | are more modes with the same screen size, only the first one is kept (see above |
170 | for more info on mode ordering). However, in very strange cases it's possible |
171 | that the first "version" of the mode doesn't work although some of the others |
172 | do -- in this case turn this switch off to see the rest. |
173 | |
174 | CONFIG_VIDEO_RETAIN - enables retaining of screen contents when switching |
175 | video modes. Works only with some boot loaders which leave enough room for the |
176 | buffer. (If you have old LILO, you can adjust heap_end_ptr and loadflags |
177 | in setup.S, but it's better to upgrade the boot loader...) |
178 | |
179 | CONFIG_VIDEO_LOCAL - enables inclusion of "local modes" in the list. The |
180 | local modes are added automatically to the beginning of the list not depending |
181 | on hardware configuration. The local modes are listed in the source text after |
182 | the "local_mode_table:" line. The comment before this line describes the format |
183 | of the table (which also includes a video card name to be displayed on the |
184 | top of the menu). |
185 | |
186 | CONFIG_VIDEO_400_HACK - force setting of 400 scan lines for standard VGA |
187 | modes. This option is intended to be used on certain buggy BIOSes which draw |
188 | some useless logo using font download and then fail to reset the correct mode. |
189 | Don't use unless needed as it forces resetting the video card. |
190 | |
191 | CONFIG_VIDEO_GFX_HACK - includes special hack for setting of graphics modes |
192 | to be used later by special drivers (e.g., 800x600 on IBM ThinkPad -- see |
193 | ftp://ftp.phys.keio.ac.jp/pub/XFree86/800x600/XF86Configs/XF86Config.IBM_TP560). |
194 | Allows to set _any_ BIOS mode including graphic ones and forcing specific |
195 | text screen resolution instead of peeking it from BIOS variables. Don't use |
196 | unless you think you know what you're doing. To activate this setup, use |
197 | mode number 0x0f08 (see section 3). |
198 | |
199 | 5. Still doesn't work? |
200 | ~~~~~~~~~~~~~~~~~~~~~~ |
201 | When the mode detection doesn't work (e.g., the mode list is incorrect or |
202 | the machine hangs instead of displaying the menu), try to switch off some of |
203 | the configuration options listed in section 4. If it fails, you can still use |
204 | your kernel with the video mode set directly via the kernel parameter. |
205 | |
206 | In either case, please send me a bug report containing what _exactly_ |
207 | happens and how do the configuration switches affect the behaviour of the bug. |
208 | |
209 | If you start Linux from M$-DOS, you might also use some DOS tools for |
210 | video mode setting. In this case, you must specify the 0x0f04 mode ("leave |
211 | current settings") to Linux, because if you don't and you use any non-standard |
212 | mode, Linux will switch to 80x25 automatically. |
213 | |
214 | If you set some extended mode and there's one or more extra lines on the |
215 | bottom of the display containing already scrolled-out text, your VGA BIOS |
216 | contains the most common video BIOS bug called "incorrect vertical display |
217 | end setting". Adding 0x8000 to the mode ID might fix the problem. Unfortunately, |
218 | this must be done manually -- no autodetection mechanisms are available. |
219 | |
220 | If you have a VGA card and your display still looks as on EGA, your BIOS |
221 | is probably broken and you need to set the CONFIG_VIDEO_400_HACK switch to |
222 | force setting of the correct mode. |
223 | |
224 | 6. History |
225 | ~~~~~~~~~~ |
226 | 1.0 (??-Nov-95) First version supporting all adapters supported by the old |
227 | setup.S + Cirrus Logic 54XX. Present in some 1.3.4? kernels |
228 | and then removed due to instability on some machines. |
229 | 2.0 (28-Jan-96) Rewritten from scratch. Cirrus Logic 64XX support added, almost |
230 | everything is configurable, the VESA support should be much more |
231 | stable, explicit mode numbering allowed, "scan" implemented etc. |
232 | 2.1 (30-Jan-96) VESA modes moved to 0x200-0x3ff. Mode selection by resolution |
233 | supported. Few bugs fixed. VESA modes are listed prior to |
234 | modes supplied by SVGA autodetection as they are more reliable. |
235 | CLGD autodetect works better. Doesn't depend on 80x25 being |
236 | active when started. Scanning fixed. 80x43 (any VGA) added. |
237 | Code cleaned up. |
238 | 2.2 (01-Feb-96) EGA 80x43 fixed. VESA extended to 0x200-0x4ff (non-standard 02XX |
239 | VESA modes work now). Display end bug workaround supported. |
240 | Special modes renumbered to allow adding of the "recalculate" |
241 | flag, 0xffff and 0xfffe became aliases instead of real IDs. |
242 | Screen contents retained during mode changes. |
243 | 2.3 (15-Mar-96) Changed to work with 1.3.74 kernel. |
244 | 2.4 (18-Mar-96) Added patches by Hans Lermen fixing a memory overwrite problem |
245 | with some boot loaders. Memory management rewritten to reflect |
246 | these changes. Unfortunately, screen contents retaining works |
247 | only with some loaders now. |
248 | Added a Tseng 132x60 mode. |
249 | 2.5 (19-Mar-96) Fixed a VESA mode scanning bug introduced in 2.4. |
250 | 2.6 (25-Mar-96) Some VESA BIOS errors not reported -- it fixes error reports on |
251 | several cards with broken VESA code (e.g., ATI VGA). |
252 | 2.7 (09-Apr-96) - Accepted all VESA modes in range 0x100 to 0x7ff, because some |
253 | cards use very strange mode numbers. |
254 | - Added Realtek VGA modes (thanks to Gonzalo Tornaria). |
255 | - Hardware testing order slightly changed, tests based on ROM |
256 | contents done as first. |
257 | - Added support for special Video7 mode switching functions |
258 | (thanks to Tom Vander Aa). |
259 | - Added 480-scanline modes (especially useful for notebooks, |
260 | original version written by hhanemaa@cs.ruu.nl, patched by |
261 | Jeff Chua, rewritten by me). |
262 | - Screen store/restore fixed. |
263 | 2.8 (14-Apr-96) - Previous release was not compilable without CONFIG_VIDEO_SVGA. |
264 | - Better recognition of text modes during mode scan. |
265 | 2.9 (12-May-96) - Ignored VESA modes 0x80 - 0xff (more VESA BIOS bugs!) |
266 | 2.10 (11-Nov-96)- The whole thing made optional. |
267 | - Added the CONFIG_VIDEO_400_HACK switch. |
268 | - Added the CONFIG_VIDEO_GFX_HACK switch. |
269 | - Code cleanup. |
270 | 2.11 (03-May-97)- Yet another cleanup, now including also the documentation. |
271 | - Direct testing of SVGA adapters turned off by default, `scan' |
272 | offered explicitly on the prompt line. |
273 | - Removed the doc section describing adding of new probing |
274 | functions as I try to get rid of _all_ hardware probing here. |
275 | 2.12 (25-May-98)- Added support for VESA frame buffer graphics. |
276 | 2.13 (14-May-99)- Minor documentation fixes. |