Documentation/fb/uvesafb.txt

   1
   2 uvesafb - A Generic Driver for VBE2+ compliant video cards
   3 ==========================================================
   4
   5 1. Requirements
   6 ---------------
   7
   8 uvesafb should work with any video card that has a Video BIOS compliant
   9 with the VBE 2.0 standard.
  10
  11 Unlike other drivers, uvesafb makes use of a userspace helper called
  12 v86d.  v86d is used to run the x86 Video BIOS code in a simulated and
  13 controlled environment.  This allows uvesafb to function on arches other
  14 than x86.  Check the v86d documentation for a list of currently supported
  15 arches.
  16
  17 v86d source code can be downloaded from the following website:
  18   http://dev.gentoo.org/~spock/projects/uvesafb
  19
  20 Please refer to the v86d documentation for detailed configuration and
  21 installation instructions.
  22
  23 Note that the v86d userspace helper has to be available at all times in
  24 order for uvesafb to work properly.  If you want to use uvesafb during
  25 early boot, you will have to include v86d into an initramfs image, and
  26 either compile it into the kernel or use it as an initrd.
  27
  28 2. Caveats and limitations
  29 --------------------------
  30
  31 uvesafb is a _generic_ driver which supports a wide variety of video
  32 cards, but which is ultimately limited by the Video BIOS interface.
  33 The 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
  46 3. Configuration
  47 ----------------
  48
  49 uvesafb can be compiled either as a module, or directly into the kernel.
  50 In both cases it supports the same set of configuration options, which
  51 are 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
  57 Accepted options:
  58
  59 ypan    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
  65 ywrap   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
  70 redraw  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
  76 vgapal  Use the standard VGA registers for palette changes.
  77
  78 pmipal  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
  82 mtrr: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
  90 nomtrr  Do not use memory type range registers.
  91
  92 vremap:n
  93         Remap 'n' MiB of video RAM.  If 0 or not specified, remap memory
  94         according to video mode.
  95
  96 vtotal: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
 105 vbemode: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
 115 nocrtc  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
 121 noedid  Do not try to fetch and use EDID-provided modes.
 122
 123 noblank Disable hardware blanking.
 124
 125 v86d: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
 131 Additionally, the following parameters may be provided.  They all override the
 132 EDID-provided values and BIOS defaults.  Refer to your monitor's specs to get
 133 the correct values for maxhf, maxvf and maxclk for your hardware.
 134
 135 maxhf:n     Maximum horizontal frequency (in kHz).
 136 maxvf:n     Maximum vertical frequency (in Hz).
 137 maxclk:n    Maximum pixel clock (in MHz).
 138
 139 4. The sysfs interface
 140 ----------------------
 141
 142 uvesafb provides several sysfs nodes for configurable parameters and
 143 additional information.
 144
 145 Driver 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
 152 Device 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
 171 5. Miscellaneous
 172 ----------------
 173
 174 Uvesafb will set a video mode with the default refresh rate and timings
 175 from 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