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-
-What is vesafb?
-===============
-
-This is a generic driver for a graphic framebuffer on intel boxes.
-
-The idea is simple: Turn on graphics mode at boot time with the help
-of the BIOS, and use this as framebuffer device /dev/fb0, like the m68k
-(and other) ports do.
-
-This means we decide at boot time whenever we want to run in text or
-graphics mode. Switching mode later on (in protected mode) is
-impossible; BIOS calls work in real mode only. VESA BIOS Extensions
-Version 2.0 are required, because we need a linear frame buffer.
-
-Advantages:
-
- * It provides a nice large console (128 cols + 48 lines with 1024x768)
- without using tiny, unreadable fonts.
- * You can run XF68_FBDev on top of /dev/fb0 (=> non-accelerated X11
- support for every VBE 2.0 compliant graphics board).
- * Most important: boot logo :-)
-
-Disadvantages:
-
- * graphic mode is slower than text mode...
-
-
-How to use it?
-==============
-
-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.
-
-X11
-===
-
-XF68_FBDev should work just fine, but it is non-accelerated. Running
-another (accelerated) X-Server like XF86_SVGA might or might not work.
-It depends on X-Server and graphics board.
-
-The X-Server must restore the video mode correctly, else you end up
-with a broken console (and vesafb cannot do anything about this).
-
-
-Refresh rates
-=============
-
-There is no way to change the vesafb video mode and/or timings after
-booting linux. If you are not happy with the 60 Hz refresh rate, you
-have these options:
-
- * configure and load the DOS-Tools for the graphics board (if
- available) and boot linux with loadlin.
- * use a native driver (matroxfb/atyfb) instead if vesafb. If none
- is available, write a new one!
- * VBE 3.0 might work too. I have neither a gfx board with VBE 3.0
- support nor the specs, so I have not checked this yet.
-
-
-Configuration
-=============
-
-The VESA BIOS provides protected mode interface for changing
-some parameters. vesafb can use it for palette changes and
-to pan the display. It is turned off by default because it
-seems not to work with some BIOS versions, but there are options
-to turn it on.
-
-You can pass options to vesafb using "video=vesafb:option" on
-the kernel command line. Multiple options should be separated
-by comma, like this: "video=vesafb:ypan,invers"
-
-Accepted options:
-
-invers no comment...
-
-ypan enable display panning using the VESA protected mode
- interface. The visible screen is just a window of the
- video memory, console scrolling is done by changing the
- start of the window.
- pro: * scrolling (fullscreen) is fast, because there is
- no need to copy around data.
- * You'll get scrollback (the Shift-PgUp thing),
- the video memory can be used as scrollback buffer
- kontra: * scrolling only parts of the screen causes some
- ugly flicker effects (boot logo flickers for
- example).
-
-ywrap Same as ypan, but assumes your gfx board can wrap-around
- the video memory (i.e. starts reading from top if it
- reaches the end of video memory). Faster than ypan.
-
-redraw scroll by redrawing the affected part of the screen, this
- is the safe (and slow) default.
-
-
-vgapal Use the standard vga registers for palette changes.
- This is the default.
-pmipal Use the protected mode interface for palette changes.
-
-mtrr:n setup memory type range registers for the vesafb framebuffer
- where n:
- 0 - disabled (equivalent to nomtrr) (default)
- 1 - uncachable
- 2 - write-back
- 3 - write-combining
- 4 - write-through
-
- If you see the following in dmesg, choose the type that matches the
- old one. In this example, use "mtrr:2".
-...
-mtrr: type mismatch for e0000000,8000000 old: write-back new: write-combining
-...
-
-nomtrr disable mtrr
-
-vremap:n
- remap 'n' MiB of video RAM. If 0 or not specified, remap memory
- according to video mode. (2.5.66 patch/idea by Antonino Daplas
- reversed to give override possibility (allocate more fb memory
- than the kernel would) to 2.4 by tmb@iki.fi)
-
-vtotal:n
- if the video BIOS of your card incorrectly determines the total
- amount of video RAM, use this option to override the BIOS (in MiB).
-
-Have fun!
-
- Gerd
-
---
-Gerd Knorr <kraxel@goldbach.in-berlin.de>
-
-Minor (mostly typo) changes
-by Nico Schmoigl <schmoigl@rumms.uni-mannheim.de>