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 19 https://github.com/mjanusz/v86d 20 21Please refer to the v86d documentation for detailed configuration and 22installation instructions. 23 24Note that the v86d userspace helper has to be available at all times in 25order for uvesafb to work properly. If you want to use uvesafb during 26early boot, you will have to include v86d into an initramfs image, and 27either compile it into the kernel or use it as an initrd. 28 292. Caveats and limitations 30-------------------------- 31 32uvesafb is a _generic_ driver which supports a wide variety of video 33cards, but which is ultimately limited by the Video BIOS interface. 34The most important limitations are: 35 36- Lack of any type of acceleration. 37- A strict and limited set of supported video modes. Often the native 38 or most optimal resolution/refresh rate for your setup will not work 39 with uvesafb, simply because the Video BIOS doesn't support the 40 video mode you want to use. This can be especially painful with 41 widescreen panels, where native video modes don't have the 4:3 aspect 42 ratio, which is what most BIOS-es are limited to. 43- Adjusting the refresh rate is only possible with a VBE 3.0 compliant 44 Video BIOS. Note that many nVidia Video BIOS-es claim to be VBE 3.0 45 compliant, while they simply ignore any refresh rate settings. 46 473. Configuration 48---------------- 49 50uvesafb can be compiled either as a module, or directly into the kernel. 51In both cases it supports the same set of configuration options, which 52are either given on the kernel command line or as module parameters, e.g.: 53 54 video=uvesafb:1024x768-32,mtrr:3,ywrap (compiled into the kernel) 55 56 # modprobe uvesafb mode_option=1024x768-32 mtrr=3 scroll=ywrap (module) 57 58Accepted options: 59 60ypan Enable display panning using the VESA protected mode 61 interface. The visible screen is just a window of the 62 video memory, console scrolling is done by changing the 63 start of the window. This option is available on x86 64 only and is the default option on that architecture. 65 66ywrap Same as ypan, but assumes your gfx board can wrap-around 67 the video memory (i.e. starts reading from top if it 68 reaches the end of video memory). Faster than ypan. 69 Available on x86 only. 70 71redraw Scroll by redrawing the affected part of the screen, this 72 is the default on non-x86. 73 74(If you're using uvesafb as a module, the above three options are 75 used a parameter of the scroll option, e.g. scroll=ypan.) 76 77vgapal Use the standard VGA registers for palette changes. 78 79pmipal Use the protected mode interface for palette changes. 80 This is the default if the protected mode interface is 81 available. Available on x86 only. 82 83mtrr:n Setup memory type range registers for the framebuffer 84 where n: 85 0 - disabled (equivalent to nomtrr) 86 3 - write-combining (default) 87 88 Values other than 0 and 3 will result in a warning and will be 89 treated just like 3. 90 91nomtrr Do not use memory type range registers. 92 93vremap:n 94 Remap 'n' MiB of video RAM. If 0 or not specified, remap memory 95 according to video mode. 96 97vtotal:n 98 If the video BIOS of your card incorrectly determines the total 99 amount of video RAM, use this option to override the BIOS (in MiB). 100 101<mode> The mode you want to set, in the standard modedb format. Refer to 102 modedb.txt for a detailed description. When uvesafb is compiled as 103 a module, the mode string should be provided as a value of the 104 'mode_option' option. 105 106vbemode:x 107 Force the use of VBE mode x. The mode will only be set if it's 108 found in the VBE-provided list of supported modes. 109 NOTE: The mode number 'x' should be specified in VESA mode number 110 notation, not the Linux kernel one (eg. 257 instead of 769). 111 HINT: If you use this option because normal <mode> parameter does 112 not work for you and you use a X server, you'll probably want to 113 set the 'nocrtc' option to ensure that the video mode is properly 114 restored after console <-> X switches. 115 116nocrtc Do not use CRTC timings while setting the video mode. This option 117 has any effect only if the Video BIOS is VBE 3.0 compliant. Use it 118 if you have problems with modes set the standard way. Note that 119 using this option implies that any refresh rate adjustments will 120 be ignored and the refresh rate will stay at your BIOS default (60 Hz). 121 122noedid Do not try to fetch and use EDID-provided modes. 123 124noblank Disable hardware blanking. 125 126v86d:path 127 Set path to the v86d executable. This option is only available as 128 a module parameter, and not as a part of the video= string. If you 129 need to use it and have uvesafb built into the kernel, use 130 uvesafb.v86d="path". 131 132Additionally, the following parameters may be provided. They all override the 133EDID-provided values and BIOS defaults. Refer to your monitor's specs to get 134the correct values for maxhf, maxvf and maxclk for your hardware. 135 136maxhf:n Maximum horizontal frequency (in kHz). 137maxvf:n Maximum vertical frequency (in Hz). 138maxclk:n Maximum pixel clock (in MHz). 139 1404. The sysfs interface 141---------------------- 142 143uvesafb provides several sysfs nodes for configurable parameters and 144additional information. 145 146Driver attributes: 147 148/sys/bus/platform/drivers/uvesafb 149 - v86d (default: /sbin/v86d) 150 Path to the v86d executable. v86d is started by uvesafb 151 if an instance of the daemon isn't already running. 152 153Device attributes: 154 155/sys/bus/platform/drivers/uvesafb/uvesafb.0 156 - nocrtc 157 Use the default refresh rate (60 Hz) if set to 1. 158 159 - oem_product_name 160 - oem_product_rev 161 - oem_string 162 - oem_vendor 163 Information about the card and its maker. 164 165 - vbe_modes 166 A list of video modes supported by the Video BIOS along with their 167 VBE mode numbers in hex. 168 169 - vbe_version 170 A BCD value indicating the implemented VBE standard. 171 1725. Miscellaneous 173---------------- 174 175Uvesafb will set a video mode with the default refresh rate and timings 176from the Video BIOS if you set pixclock to 0 in fb_var_screeninfo. 177 178 179-- 180 Michal Januszewski <spock@gentoo.org> 181 Last updated: 2017-10-10 182 183 Documentation of the uvesafb options is loosely based on vesafb.txt. 184 185
