1 2uvesafb - A Generic Driver for VBE2+ compliant video cards 3========================================================== 4 51. Requirements 6--------------- 7 8uvesafb should work with any video card that has a Video BIOS compliant 9with the VBE 2.0 standard. 10 11Unlike other drivers, uvesafb makes use of a userspace helper called 12v86d. v86d is used to run the x86 Video BIOS code in a simulated and 13controlled environment. This allows uvesafb to function on arches other 14than x86. Check the v86d documentation for a list of currently supported 15arches. 16 17v86d source code can be downloaded from the following website: 18 http://dev.gentoo.org/~spock/projects/uvesafb 19 20Please refer to the v86d documentation for detailed configuration and 21installation instructions. 22 23Note that the v86d userspace helper has to be available at all times in 24order for uvesafb to work properly. If you want to use uvesafb during 25early boot, you will have to include v86d into an initramfs image, and 26either compile it into the kernel or use it as an initrd. 27 282. Caveats and limitations 29-------------------------- 30 31uvesafb is a _generic_ driver which supports a wide variety of video 32cards, but which is ultimately limited by the Video BIOS interface. 33The most important limitations are: 34 35- Lack of any type of acceleration. 36- A strict and limited set of supported video modes. Often the native 37 or most optimal resolution/refresh rate for your setup will not work 38 with uvesafb, simply because the Video BIOS doesn't support the 39 video mode you want to use. This can be especially painful with 40 widescreen panels, where native video modes don't have the 4:3 aspect 41 ratio, which is what most BIOS-es are limited to. 42- Adjusting the refresh rate is only possible with a VBE 3.0 compliant 43 Video BIOS. Note that many nVidia Video BIOS-es claim to be VBE 3.0 44 compliant, while they simply ignore any refresh rate settings. 45 463. Configuration 47---------------- 48 49uvesafb can be compiled either as a module, or directly into the kernel. 50In both cases it supports the same set of configuration options, which 51are either given on the kernel command line or as module parameters, e.g.: 52 53 video=uvesafb:1024x768-32,mtrr:3,ywrap (compiled into the kernel) 54 55 # modprobe uvesafb mode_option=1024x768-32 mtrr=3 scroll=ywrap (module) 56 57Accepted options: 58 59ypan Enable display panning using the VESA protected mode 60 interface. The visible screen is just a window of the 61 video memory, console scrolling is done by changing the 62 start of the window. This option is available on x86 63 only and is the default option on that architecture. 64 65ywrap Same as ypan, but assumes your gfx board can wrap-around 66 the video memory (i.e. starts reading from top if it 67 reaches the end of video memory). Faster than ypan. 68 Available on x86 only. 69 70redraw Scroll by redrawing the affected part of the screen, this 71 is the default on non-x86. 72 73(If you're using uvesafb as a module, the above three options are 74 used a parameter of the scroll option, e.g. scroll=ypan.) 75 76vgapal Use the standard VGA registers for palette changes. 77 78pmipal Use the protected mode interface for palette changes. 79 This is the default if the protected mode interface is 80 available. Available on x86 only. 81 82mtrr:n Setup memory type range registers for the framebuffer 83 where n: 84 0 - disabled (equivalent to nomtrr) 85 3 - write-combining (default) 86 87 Values other than 0 and 3 will result in a warning and will be 88 treated just like 3. 89 90nomtrr Do not use memory type range registers. 91 92vremap:n 93 Remap 'n' MiB of video RAM. If 0 or not specified, remap memory 94 according to video mode. 95 96vtotal:n 97 If the video BIOS of your card incorrectly determines the total 98 amount of video RAM, use this option to override the BIOS (in MiB). 99 100<mode> The mode you want to set, in the standard modedb format. Refer to 101 modedb.txt for a detailed description. When uvesafb is compiled as 102 a module, the mode string should be provided as a value of the 103 'mode_option' option. 104 105vbemode:x 106 Force the use of VBE mode x. The mode will only be set if it's 107 found in the VBE-provided list of supported modes. 108 NOTE: The mode number 'x' should be specified in VESA mode number 109 notation, not the Linux kernel one (eg. 257 instead of 769). 110 HINT: If you use this option because normal <mode> parameter does 111 not work for you and you use a X server, you'll probably want to 112 set the 'nocrtc' option to ensure that the video mode is properly 113 restored after console <-> X switches. 114 115nocrtc Do not use CRTC timings while setting the video mode. This option 116 has any effect only if the Video BIOS is VBE 3.0 compliant. Use it 117 if you have problems with modes set the standard way. Note that 118 using this option implies that any refresh rate adjustments will 119 be ignored and the refresh rate will stay at your BIOS default (60 Hz). 120 121noedid Do not try to fetch and use EDID-provided modes. 122 123noblank Disable hardware blanking. 124 125v86d:path 126 Set path to the v86d executable. This option is only available as 127 a module parameter, and not as a part of the video= string. If you 128 need to use it and have uvesafb built into the kernel, use 129 uvesafb.v86d="path". 130 131Additionally, the following parameters may be provided. They all override the 132EDID-provided values and BIOS defaults. Refer to your monitor's specs to get 133the correct values for maxhf, maxvf and maxclk for your hardware. 134 135maxhf:n Maximum horizontal frequency (in kHz). 136maxvf:n Maximum vertical frequency (in Hz). 137maxclk:n Maximum pixel clock (in MHz). 138 1394. The sysfs interface 140---------------------- 141 142uvesafb provides several sysfs nodes for configurable parameters and 143additional information. 144 145Driver attributes: 146 147/sys/bus/platform/drivers/uvesafb 148 - v86d (default: /sbin/v86d) 149 Path to the v86d executable. v86d is started by uvesafb 150 if an instance of the daemon isn't already running. 151 152Device attributes: 153 154/sys/bus/platform/drivers/uvesafb/uvesafb.0 155 - nocrtc 156 Use the default refresh rate (60 Hz) if set to 1. 157 158 - oem_product_name 159 - oem_product_rev 160 - oem_string 161 - oem_vendor 162 Information about the card and its maker. 163 164 - vbe_modes 165 A list of video modes supported by the Video BIOS along with their 166 VBE mode numbers in hex. 167 168 - vbe_version 169 A BCD value indicating the implemented VBE standard. 170 1715. Miscellaneous 172---------------- 173 174Uvesafb will set a video mode with the default refresh rate and timings 175from the Video BIOS if you set pixclock to 0 in fb_var_screeninfo. 176 177 178-- 179 Michal Januszewski <spock@gentoo.org> 180 Last updated: 2009-03-30 181 182 Documentation of the uvesafb options is loosely based on vesafb.txt. 183 184