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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 | 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 Extentions 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 descired 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 becauce your BIOS does not support linear framebuffers or becauce it does not support this mode at all. Even if your board does, it might be the BIOS which does not. VESA BIOS Extentions 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). Configuration ============= You can pass kernel command line options to vesafb with "video=vesa:option1". Multiple options should be separated by comma. Accepted options: invers - no comment... redraw - scroll by redrawing the affected part of the screen ypan - enable display panning using the VESA protected mode interface. This enables the Shift-PgUp scrollback thing and greatly speeds up fullscreen scrolling. It is slower than "redraw" when scrolling only a halve screen. This is the default. ywrap - If your gfx board supports wrap-around, use this one instead of ypan. nopal - Don't use the protected mode interface for palette changes. vesafb will try the standard vga registers instead. Have fun! Gerd -- Gerd Knorr <kraxel@cs.tu-berlin.de> Minor (mostly typo) changes by Nico Schmoigl <schmoigl@rumms.uni-mannheim.de> |