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1==========================================================2uvesafb - A Generic Driver for VBE2+ compliant video cards3==========================================================4 51. Requirements6---------------7 8uvesafb should work with any video card that has a Video BIOS compliant9with the VBE 2.0 standard.10 11Unlike other drivers, uvesafb makes use of a userspace helper called12v86d. v86d is used to run the x86 Video BIOS code in a simulated and13controlled environment. This allows uvesafb to function on arches other14than x86. Check the v86d documentation for a list of currently supported15arches.16 17v86d source code can be downloaded from the following website:18 19 https://github.com/mjanusz/v86d20 21Please refer to the v86d documentation for detailed configuration and22installation instructions.23 24Note that the v86d userspace helper has to be available at all times in25order for uvesafb to work properly. If you want to use uvesafb during26early boot, you will have to include v86d into an initramfs image, and27either compile it into the kernel or use it as an initrd.28 292. Caveats and limitations30--------------------------31 32uvesafb is a _generic_ driver which supports a wide variety of video33cards, 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 native38 or most optimal resolution/refresh rate for your setup will not work39 with uvesafb, simply because the Video BIOS doesn't support the40 video mode you want to use. This can be especially painful with41 widescreen panels, where native video modes don't have the 4:3 aspect42 ratio, which is what most BIOS-es are limited to.43- Adjusting the refresh rate is only possible with a VBE 3.0 compliant44 Video BIOS. Note that many nVidia Video BIOS-es claim to be VBE 3.045 compliant, while they simply ignore any refresh rate settings.46 473. Configuration48----------------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, which52are 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 60======= =========================================================61ypan Enable display panning using the VESA protected mode62 interface. The visible screen is just a window of the63 video memory, console scrolling is done by changing the64 start of the window. This option is available on x8665 only and is the default option on that architecture.66 67ywrap Same as ypan, but assumes your gfx board can wrap-around68 the video memory (i.e. starts reading from top if it69 reaches the end of video memory). Faster than ypan.70 Available on x86 only.71 72redraw Scroll by redrawing the affected part of the screen, this73 is the default on non-x86.74======= =========================================================75 76(If you're using uvesafb as a module, the above three options are77used a parameter of the scroll option, e.g. scroll=ypan.)78 79=========== ====================================================================80vgapal Use the standard VGA registers for palette changes.81 82pmipal Use the protected mode interface for palette changes.83 This is the default if the protected mode interface is84 available. Available on x86 only.85 86mtrr:n Setup memory type range registers for the framebuffer87 where n:88 89 - 0 - disabled (equivalent to nomtrr)90 - 3 - write-combining (default)91 92 Values other than 0 and 3 will result in a warning and will be93 treated just like 3.94 95nomtrr Do not use memory type range registers.96 97vremap:n98 Remap 'n' MiB of video RAM. If 0 or not specified, remap memory99 according to video mode.100 101vtotal:n If the video BIOS of your card incorrectly determines the total102 amount of video RAM, use this option to override the BIOS (in MiB).103 104<mode> The mode you want to set, in the standard modedb format. Refer to105 modedb.txt for a detailed description. When uvesafb is compiled as106 a module, the mode string should be provided as a value of the107 'mode_option' option.108 109vbemode:x Force the use of VBE mode x. The mode will only be set if it's110 found in the VBE-provided list of supported modes.111 NOTE: The mode number 'x' should be specified in VESA mode number112 notation, not the Linux kernel one (eg. 257 instead of 769).113 HINT: If you use this option because normal <mode> parameter does114 not work for you and you use a X server, you'll probably want to115 set the 'nocrtc' option to ensure that the video mode is properly116 restored after console <-> X switches.117 118nocrtc Do not use CRTC timings while setting the video mode. This option119 has any effect only if the Video BIOS is VBE 3.0 compliant. Use it120 if you have problems with modes set the standard way. Note that121 using this option implies that any refresh rate adjustments will122 be ignored and the refresh rate will stay at your BIOS default123 (60 Hz).124 125noedid Do not try to fetch and use EDID-provided modes.126 127noblank Disable hardware blanking.128 129v86d:path Set path to the v86d executable. This option is only available as130 a module parameter, and not as a part of the video= string. If you131 need to use it and have uvesafb built into the kernel, use132 uvesafb.v86d="path".133=========== ====================================================================134 135Additionally, the following parameters may be provided. They all override the136EDID-provided values and BIOS defaults. Refer to your monitor's specs to get137the correct values for maxhf, maxvf and maxclk for your hardware.138 139=========== ======================================140maxhf:n Maximum horizontal frequency (in kHz).141maxvf:n Maximum vertical frequency (in Hz).142maxclk:n Maximum pixel clock (in MHz).143=========== ======================================144 1454. The sysfs interface146----------------------147 148uvesafb provides several sysfs nodes for configurable parameters and149additional information.150 151Driver attributes:152 153/sys/bus/platform/drivers/uvesafb154 v86d155 (default: /sbin/v86d)156 157 Path to the v86d executable. v86d is started by uvesafb158 if an instance of the daemon isn't already running.159 160Device attributes:161 162/sys/bus/platform/drivers/uvesafb/uvesafb.0163 nocrtc164 Use the default refresh rate (60 Hz) if set to 1.165 166 oem_product_name, oem_product_rev, oem_string, oem_vendor167 Information about the card and its maker.168 169 vbe_modes170 A list of video modes supported by the Video BIOS along with their171 VBE mode numbers in hex.172 173 vbe_version174 A BCD value indicating the implemented VBE standard.175 1765. Miscellaneous177----------------178 179Uvesafb will set a video mode with the default refresh rate and timings180from the Video BIOS if you set pixclock to 0 in fb_var_screeninfo.181 182 183 184 Michal Januszewski <spock@gentoo.org>185 186 Last updated: 2017-10-10187 188 Documentation of the uvesafb options is loosely based on vesafb.txt.189