mirror of
https://kernel.googlesource.com/pub/scm/linux/kernel/git/stable/linux-stable.git
synced 2025-11-04 07:44:51 +10:00
ab42b81895
The conversion is actually: - add blank lines and identation in order to identify paragraphs; - fix tables markups; - add some lists markups; - mark literal blocks; - adjust title markups. At its new index.rst, let's add a :orphan: while this is not linked to the main index.rst file, in order to avoid build warnings. Also, removed the Maintained by, as requested by Geert. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
189 lines
7.2 KiB
ReStructuredText
189 lines
7.2 KiB
ReStructuredText
==========================================================
|
|
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:
|
|
|
|
https://github.com/mjanusz/v86d
|
|
|
|
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_option=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. This option is available on x86
|
|
only and is the default option on that architecture.
|
|
|
|
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 default on non-x86.
|
|
======= =========================================================
|
|
|
|
(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)
|
|
- 3 - write-combining (default)
|
|
|
|
Values other than 0 and 3 will result in a warning and will be
|
|
treated just like 3.
|
|
|
|
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' 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: 2017-10-10
|
|
|
|
Documentation of the uvesafb options is loosely based on vesafb.txt.
|