uvesafb: documentation
Documentation for the uvesafb driver. Signed-off-by: Michal Januszewski <spock@gentoo.org> Signed-off-by: Antonino Daplas <adaplas@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Michal Januszewski
Linus Torvalds
parent
8bdb3a2d7d
commit
0a0b53f660
1 changed files with 188 additions and 0 deletions
188
Documentation/fb/uvesafb.txt
Normal file
188
Documentation/fb/uvesafb.txt
Normal file
|
|
@ -0,0 +1,188 @@
|
|||
|
||||
uvesafb - A Generic Driver for VBE2+ compliant video cards
|
||||
==========================================================
|
||||
|
||||
1. Requirements
|
||||
---------------
|
||||
|
||||
uvesafb should work with any video card that has a Video BIOS compliant
|
||||
with the VBE 2.0 standard.
|
||||
|
||||
Unlike other drivers, uvesafb makes use of a userspace helper called
|
||||
v86d. v86d is used to run the x86 Video BIOS code in a simulated and
|
||||
controlled environment. This allows uvesafb to function on arches other
|
||||
than x86. Check the v86d documentation for a list of currently supported
|
||||
arches.
|
||||
|
||||
v86d source code can be downloaded from the following website:
|
||||
http://dev.gentoo.org/~spock/projects/uvesafb
|
||||
|
||||
Please refer to the v86d documentation for detailed configuration and
|
||||
installation instructions.
|
||||
|
||||
Note that the v86d userspace helper has to be available at all times in
|
||||
order for uvesafb to work properly. If you want to use uvesafb during
|
||||
early boot, you will have to include v86d into an initramfs image, and
|
||||
either compile it into the kernel or use it as an initrd.
|
||||
|
||||
2. Caveats and limitations
|
||||
--------------------------
|
||||
|
||||
uvesafb is a _generic_ driver which supports a wide variety of video
|
||||
cards, but which is ultimately limited by the Video BIOS interface.
|
||||
The most important limitations are:
|
||||
|
||||
- Lack of any type of acceleration.
|
||||
- A strict and limited set of supported video modes. Often the native
|
||||
or most optimal resolution/refresh rate for your setup will not work
|
||||
with uvesafb, simply because the Video BIOS doesn't support the
|
||||
video mode you want to use. This can be especially painful with
|
||||
widescreen panels, where native video modes don't have the 4:3 aspect
|
||||
ratio, which is what most BIOS-es are limited to.
|
||||
- Adjusting the refresh rate is only possible with a VBE 3.0 compliant
|
||||
Video BIOS. Note that many nVidia Video BIOS-es claim to be VBE 3.0
|
||||
compliant, while they simply ignore any refresh rate settings.
|
||||
|
||||
3. Configuration
|
||||
----------------
|
||||
|
||||
uvesafb can be compiled either as a module, or directly into the kernel.
|
||||
In both cases it supports the same set of configuration options, which
|
||||
are either given on the kernel command line or as module parameters, e.g.:
|
||||
|
||||
video=uvesafb:1024x768-32,mtrr:3,ywrap (compiled into the kernel)
|
||||
|
||||
# modprobe uvesafb mode=1024x768-32 mtrr=3 scroll=ywrap (module)
|
||||
|
||||
Accepted options:
|
||||
|
||||
ypan Enable display panning using the VESA protected mode
|
||||
interface. The visible screen is just a window of the
|
||||
video memory, console scrolling is done by changing the
|
||||
start of the window. Available on x86 only.
|
||||
|
||||
ywrap Same as ypan, but assumes your gfx board can wrap-around
|
||||
the video memory (i.e. starts reading from top if it
|
||||
reaches the end of video memory). Faster than ypan.
|
||||
Available on x86 only.
|
||||
|
||||
redraw Scroll by redrawing the affected part of the screen, this
|
||||
is the safe (and slow) default.
|
||||
|
||||
(If you're using uvesafb as a module, the above three options are
|
||||
used a parameter of the scroll option, e.g. scroll=ypan.)
|
||||
|
||||
vgapal Use the standard VGA registers for palette changes.
|
||||
|
||||
pmipal Use the protected mode interface for palette changes.
|
||||
This is the default if the protected mode interface is
|
||||
available. Available on x86 only.
|
||||
|
||||
mtrr:n Setup memory type range registers for the framebuffer
|
||||
where n:
|
||||
0 - disabled (equivalent to nomtrr) (default)
|
||||
1 - uncachable
|
||||
2 - write-back
|
||||
3 - write-combining
|
||||
4 - write-through
|
||||
|
||||
If you see the following in dmesg, choose the type that matches
|
||||
the old one. In this example, use "mtrr:2".
|
||||
...
|
||||
mtrr: type mismatch for e0000000,8000000 old: write-back new: write-combining
|
||||
...
|
||||
|
||||
nomtrr Do not use memory type range registers.
|
||||
|
||||
vremap:n
|
||||
Remap 'n' MiB of video RAM. If 0 or not specified, remap memory
|
||||
according to video mode.
|
||||
|
||||
vtotal:n
|
||||
If the video BIOS of your card incorrectly determines the total
|
||||
amount of video RAM, use this option to override the BIOS (in MiB).
|
||||
|
||||
<mode> The mode you want to set, in the standard modedb format. Refer to
|
||||
modedb.txt for a detailed description. When uvesafb is compiled as
|
||||
a module, the mode string should be provided as a value of the
|
||||
'mode' option.
|
||||
|
||||
vbemode:x
|
||||
Force the use of VBE mode x. The mode will only be set if it's
|
||||
found in the VBE-provided list of supported modes.
|
||||
NOTE: The mode number 'x' should be specified in VESA mode number
|
||||
notation, not the Linux kernel one (eg. 257 instead of 769).
|
||||
HINT: If you use this option because normal <mode> parameter does
|
||||
not work for you and you use a X server, you'll probably want to
|
||||
set the 'nocrtc' option to ensure that the video mode is properly
|
||||
restored after console <-> X switches.
|
||||
|
||||
nocrtc Do not use CRTC timings while setting the video mode. This option
|
||||
has any effect only if the Video BIOS is VBE 3.0 compliant. Use it
|
||||
if you have problems with modes set the standard way. Note that
|
||||
using this option implies that any refresh rate adjustments will
|
||||
be ignored and the refresh rate will stay at your BIOS default (60 Hz).
|
||||
|
||||
noedid Do not try to fetch and use EDID-provided modes.
|
||||
|
||||
noblank Disable hardware blanking.
|
||||
|
||||
v86d:path
|
||||
Set path to the v86d executable. This option is only available as
|
||||
a module parameter, and not as a part of the video= string. If you
|
||||
need to use it and have uvesafb built into the kernel, use
|
||||
uvesafb.v86d="path".
|
||||
|
||||
Additionally, the following parameters may be provided. They all override the
|
||||
EDID-provided values and BIOS defaults. Refer to your monitor's specs to get
|
||||
the correct values for maxhf, maxvf and maxclk for your hardware.
|
||||
|
||||
maxhf:n Maximum horizontal frequency (in kHz).
|
||||
maxvf:n Maximum vertical frequency (in Hz).
|
||||
maxclk:n Maximum pixel clock (in MHz).
|
||||
|
||||
4. The sysfs interface
|
||||
----------------------
|
||||
|
||||
uvesafb provides several sysfs nodes for configurable parameters and
|
||||
additional information.
|
||||
|
||||
Driver attributes:
|
||||
|
||||
/sys/bus/platform/drivers/uvesafb
|
||||
- v86d (default: /sbin/v86d)
|
||||
Path to the v86d executable. v86d is started by uvesafb
|
||||
if an instance of the daemon isn't already running.
|
||||
|
||||
Device attributes:
|
||||
|
||||
/sys/bus/platform/drivers/uvesafb/uvesafb.0
|
||||
- nocrtc
|
||||
Use the default refresh rate (60 Hz) if set to 1.
|
||||
|
||||
- oem_product_name
|
||||
- oem_product_rev
|
||||
- oem_string
|
||||
- oem_vendor
|
||||
Information about the card and its maker.
|
||||
|
||||
- vbe_modes
|
||||
A list of video modes supported by the Video BIOS along with their
|
||||
VBE mode numbers in hex.
|
||||
|
||||
- vbe_version
|
||||
A BCD value indicating the implemented VBE standard.
|
||||
|
||||
5. Miscellaneous
|
||||
----------------
|
||||
|
||||
Uvesafb will set a video mode with the default refresh rate and timings
|
||||
from the Video BIOS if you set pixclock to 0 in fb_var_screeninfo.
|
||||
|
||||
|
||||
--
|
||||
Michal Januszewski <spock@gentoo.org>
|
||||
Last updated: 2007-06-16
|
||||
|
||||
Documentation of the uvesafb options is loosely based on vesafb.txt.
|
||||
|
||||
Loading…
Reference in a new issue