Re: kernel/vesa video modes
On Wed, 2006-09-06 at 14:51 -0500, T.J. Duchene wrote:
> > I use the "vga=792" parameter at the end of the "kernel" line in grub,
> > so that the resolution is changed to 1024x768 at 24 bit. I would like
> > to use 1280x960 at 24 bit instead, but haven't been able to find how to
> > anywhere. All the tables I've found exclude 1280x960. Does anyone know
> > what I need to use after "vga="?
> >
> > Running Debian Etch on amd64
>
> The best place to find the documentation on the video modes is in the
> kernel documentation. I normally get mine straight from kernel.org,
> but then I prefer to roll my own kernels, as I often find the default
> kernels troublesome for my situation. I'd imagine you can find it in
> the Debian kernel packages.
Okay, I have the kernel documentation from the linux-doc-2.6.16 package.
> However you get them, look for the vesa and framebuffer (fb) text files
> under the Documentation directory of the kernel source code.
I didn't find anything. I don't understand how the COLSxROWS when I use
vga=ask relates to resolution/depth.
I attached the applicable parts of vesafb.txt and svga.txt; hopefully no
one minds.
> I think though, that modes above 1024x768 were not defined in the original
> VESA standard. Don't quote me though, I've been wrong before.
1280x1024 is there, but not 1280x960.
I found this in an old message from this list: "hwinfo --framebuffer".
Its output is:
===========
02: None 00.0: 11001 VESA Framebuffer
[Created at bios.440]
Unique ID: rdCR.WMLw7opB9q6
Hardware Class: framebuffer
Model: "NVIDIA nv44 Board - p262h0 "
Vendor: "NVIDIA Corporation"
Device: "nv44 Board - p262h0 "
SubVendor: "NVIDIA"
SubDevice:
Revision: "Chip Rev"
Memory Size: 128 MB
Memory Range: 0xc0000000-0xc7ffffff (rw)
Mode 0x0300: 640x400 (+640), 8 bits
Mode 0x0301: 640x480 (+640), 8 bits
Mode 0x0303: 800x600 (+800), 8 bits
Mode 0x0305: 1024x768 (+1024), 8 bits
Mode 0x0307: 1280x1024 (+1280), 8 bits
Mode 0x030e: 320x200 (+640), 16 bits
Mode 0x030f: 320x200 (+1280), 24 bits
Mode 0x0311: 640x480 (+1280), 16 bits
Mode 0x0312: 640x480 (+2560), 24 bits
Mode 0x0314: 800x600 (+1600), 16 bits
Mode 0x0315: 800x600 (+3200), 24 bits
Mode 0x0317: 1024x768 (+2048), 16 bits
Mode 0x0318: 1024x768 (+4096), 24 bits
Mode 0x031a: 1280x1024 (+2560), 16 bits
Mode 0x031b: 1280x1024 (+5120), 24 bits
Mode 0x0330: 320x200 (+320), 8 bits
Mode 0x0331: 320x400 (+320), 8 bits
Mode 0x0332: 320x400 (+640), 16 bits
Mode 0x0333: 320x400 (+1280), 24 bits
Mode 0x0334: 320x240 (+320), 8 bits
Mode 0x0335: 320x240 (+640), 16 bits
Mode 0x0336: 320x240 (+1280), 24 bits
Mode 0x033d: 640x400 (+1280), 16 bits
Mode 0x033e: 640x400 (+2560), 24 bits
Mode 0x0345: 1600x1200 (+1600), 8 bits
Mode 0x0346: 1600x1200 (+3200), 16 bits
Mode 0x0347: 1400x1050 (+1400), 8 bits
Mode 0x0348: 1400x1050 (+2800), 16 bits
Mode 0x0352: 2048x1536 (+8192), 24 bits
Config Status: cfg=new, avail=yes, need=no, active=unknown
=================
So I'm assuming that I can't use 1280x960. That doesn't make sense to
me, but whatever...
This small document describes the "Video Mode Selection" feature which
allows the use of various special video modes supported by the video BIOS. Due
to usage of the BIOS, the selection is limited to boot time (before the
kernel decompression starts) and works only on 80X86 machines.
** Short intro for the impatient: Just use vga=ask for the first time,
** enter `scan' on the video mode prompt, pick the mode you want to use,
** remember its mode ID (the four-digit hexadecimal number) and then
** set the vga parameter to this number (converted to decimal first).
The video mode to be used is selected by a kernel parameter which can be
specified in the kernel Makefile (the SVGA_MODE=... line) or by the "vga=..."
option of LILO (or some other boot loader you use) or by the "vidmode" utility
(present in standard Linux utility packages). You can use the following values
of this parameter:
NORMAL_VGA - Standard 80x25 mode available on all display adapters.
EXTENDED_VGA - Standard 8-pixel font mode: 80x43 on EGA, 80x50 on VGA.
ASK_VGA - Display a video mode menu upon startup (see below).
0..35 - Menu item number (when you have used the menu to view the list of
modes available on your adapter, you can specify the menu item you want
to use). 0..9 correspond to "0".."9", 10..35 to "a".."z". Warning: the
mode list displayed may vary as the kernel version changes, because the
modes are listed in a "first detected -- first displayed" manner. It's
better to use absolute mode numbers instead.
0x.... - Hexadecimal video mode ID (also displayed on the menu, see below
for exact meaning of the ID). Warning: rdev and LILO don't support
hexadecimal numbers -- you have to convert it to decimal manually.
2. Menu
~~~~~~~
The ASK_VGA mode causes the kernel to offer a video mode menu upon
bootup. It displays a "Press <RETURN> to see video modes available, <SPACE>
to continue or wait 30 secs" message. If you press <RETURN>, you enter the
menu, if you press <SPACE> or wait 30 seconds, the kernel will boot up in
the standard 80x25 mode.
The menu looks like:
Video adapter: <name-of-detected-video-adapter>
Mode: COLSxROWS:
0 0F00 80x25
1 0F01 80x50
2 0F02 80x43
3 0F03 80x26
....
Enter mode number or `scan': <flashing-cursor-here>
<name-of-detected-video-adapter> tells what video adapter did Linux detect
-- it's either a generic adapter name (MDA, CGA, HGC, EGA, VGA, VESA VGA [a VGA
with VESA-compliant BIOS]) or a chipset name (e.g., Trident). Direct detection
of chipsets is turned off by default (see CONFIG_VIDEO_SVGA in chapter 4 to see
how to enable it if you really want) as it's inherently unreliable due to
absolutely insane PC design.
"0 0F00 80x25" means that the first menu item (the menu items are numbered
from "0" to "9" and from "a" to "z") is a 80x25 mode with ID=0x0f00 (see the
next section for a description of mode IDs).
<flashing-cursor-here> encourages you to enter the item number or mode ID
you wish to set and press <RETURN>. If the computer complains something about
"Unknown mode ID", it is trying to tell you that it isn't possible to set such
a mode. It's also possible to press only <RETURN> which leaves the current mode.
The mode list usually contains a few basic modes and some VESA modes. In
case your chipset has been detected, some chipset-specific modes are shown as
well (some of these might be missing or unusable on your machine as different
BIOSes are often shipped with the same card and the mode numbers depend purely
on the VGA BIOS).
The modes displayed on the menu are partially sorted: The list starts with
the standard modes (80x25 and 80x50) followed by "special" modes (80x28 and
80x43), local modes (if the local modes feature is enabled), VESA modes and
finally SVGA modes for the auto-detected adapter.
If you are not happy with the mode list offered (e.g., if you think your card
is able to do more), you can enter "scan" instead of item number / mode ID. The
program will try to ask the BIOS for all possible video mode numbers and test
what happens then. The screen will be probably flashing wildly for some time and
strange noises will be heard from inside the monitor and so on and then, really
all consistent video modes supported by your BIOS will appear (plus maybe some
`ghost modes'). If you are afraid this could damage your monitor, don't use this
function.
After scanning, the mode ordering is a bit different: the auto-detected SVGA
modes are not listed at all and the modes revealed by `scan' are shown before
all VESA modes.
3. Mode IDs
~~~~~~~~~~~
Because of the complexity of all the video stuff, the video mode IDs
used here are also a bit complex. A video mode ID is a 16-bit number usually
expressed in a hexadecimal notation (starting with "0x"). You can set a mode
by entering its mode directly if you know it even if it isn't shown on the menu.
The ID numbers can be divided to three regions:
0x0000 to 0x00ff - menu item references. 0x0000 is the first item. Don't use
outside the menu as this can change from boot to boot (especially if you
have used the `scan' feature).
0x0100 to 0x017f - standard BIOS modes. The ID is a BIOS video mode number
(as presented to INT 10, function 00) increased by 0x0100.
0x0200 to 0x08ff - VESA BIOS modes. The ID is a VESA mode ID increased by
0x0100. All VESA modes should be autodetected and shown on the menu.
0x0900 to 0x09ff - Video7 special modes. Set by calling INT 0x10, AX=0x6f05.
(Usually 940=80x43, 941=132x25, 942=132x44, 943=80x60, 944=100x60,
945=132x28 for the standard Video7 BIOS)
0x0f00 to 0x0fff - special modes (they are set by various tricks -- usually
by modifying one of the standard modes). Currently available:
0x0f00 standard 80x25, don't reset mode if already set (=FFFF)
0x0f01 standard with 8-point font: 80x43 on EGA, 80x50 on VGA
0x0f02 VGA 80x43 (VGA switched to 350 scanlines with a 8-point font)
0x0f03 VGA 80x28 (standard VGA scans, but 14-point font)
0x0f04 leave current video mode
0x0f05 VGA 80x30 (480 scans, 16-point font)
0x0f06 VGA 80x34 (480 scans, 14-point font)
0x0f07 VGA 80x60 (480 scans, 8-point font)
0x0f08 Graphics hack (see the CONFIG_VIDEO_HACK paragraph below)
0x1000 to 0x7fff - modes specified by resolution. The code has a "0xRRCC"
form where RR is a number of rows and CC is a number of columns.
E.g., 0x1950 corresponds to a 80x25 mode, 0x2b84 to 132x43 etc.
This is the only fully portable way to refer to a non-standard mode,
but it relies on the mode being found and displayed on the menu
(remember that mode scanning is not done automatically).
0xff00 to 0xffff - aliases for backward compatibility:
0xffff equivalent to 0x0f00 (standard 80x25)
0xfffe equivalent to 0x0f01 (EGA 80x43 or VGA 80x50)
If you add 0x8000 to the mode ID, the program will try to recalculate
vertical display timing according to mode parameters, which can be used to
eliminate some annoying bugs of certain VGA BIOSes (usually those used for
cards with S3 chipsets and old Cirrus Logic BIOSes) -- mainly extra lines at the
end of the display.
Switching modes is done using the vga=... boot parameter. Read
Documentation/svga.txt for details.
You should compile in both vgacon (for text mode) and vesafb (for
graphics mode). Which of them takes over the console depends on
whenever the specified mode is text or graphics.
The graphic modes are NOT in the list which you get if you boot with
vga=ask and hit return. The mode you wish to use is derived from the
VESA mode number. Here are those VESA mode numbers:
| 640x480 800x600 1024x768 1280x1024
----+-------------------------------------
256 | 0x101 0x103 0x105 0x107
32k | 0x110 0x113 0x116 0x119
64k | 0x111 0x114 0x117 0x11A
16M | 0x112 0x115 0x118 0x11B
The video mode number of the Linux kernel is the VESA mode number plus
0x200.
Linux_kernel_mode_number = VESA_mode_number + 0x200
So the table for the Kernel mode numbers are:
| 640x480 800x600 1024x768 1280x1024
----+-------------------------------------
256 | 0x301 0x303 0x305 0x307
32k | 0x310 0x313 0x316 0x319
64k | 0x311 0x314 0x317 0x31A
16M | 0x312 0x315 0x318 0x31B
To enable one of those modes you have to specify "vga=ask" in the
lilo.conf file and rerun LILO. Then you can type in the desired
mode at the "vga=ask" prompt. For example if you like to use
1024x768x256 colors you have to say "305" at this prompt.
If this does not work, this might be because your BIOS does not support
linear framebuffers or because it does not support this mode at all.
Even if your board does, it might be the BIOS which does not. VESA BIOS
Extensions v2.0 are required, 1.2 is NOT sufficient. You will get a
"bad mode number" message if something goes wrong.
1. Note: LILO cannot handle hex, for booting directly with
"vga=mode-number" you have to transform the numbers to decimal.
2. Note: Some newer versions of LILO appear to work with those hex values,
if you set the 0x in front of the numbers.
Reply to: