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Commit 4ff45f51 authored by Sylvain Meyer's avatar Sylvain Meyer Committed by Linus Torvalds

[PATCH] intelfb documentation

Add a small documentation of the driver parameters.
Signed-off-by: default avatarSylvain Meyer <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent df529338
Intel 830M/845G/852GM/855GM/865G/915G Framebuffer driver
A. Introduction
This is a framebuffer driver for various Intel 810/815 compatible
graphics devices. These would include:
Intel 830M
Intel 810E845G
Intel 852GM
Intel 855GM
Intel 865G
Intel 915G
B. List of available options
a. "video=intelfb"
enables the intelfb driver
Recommendation: required
b. "mode=<xres>x<yres>[-<bpp>][@<refresh>]"
select mode
Recommendation: user preference
(default = 1024x768-32@70)
c. "vram=<value>"
select amount of system RAM in MB to allocate for the video memory
if not enough RAM was already allocated by the BIOS.
Recommendation: 1 - 4 MB.
(default = 4 MB)
d. "voffset=<value>"
select at what offset in MB of the logical memory to allocate the
framebuffer memory. The intent is to avoid the memory blocks
used by standard graphics applications (XFree86). Depending on your
usage, adjust the value up or down, (0 for maximum usage, 63/127 MB
for the least amount). Note, an arbitrary setting may conflict
with XFree86.
Recommendation: do not set
(default = 48 MB)
e. "accel"
enable text acceleration. This can be enabled/reenabled anytime
by using 'fbset -accel true/false'.
Recommendation: enable
(default = set)
f. "hwcursor"
enable cursor acceleration.
Recommendation: enable
(default = set)
g. "mtrr"
enable MTRR. This allows data transfers to the framebuffer memory
to occur in bursts which can significantly increase performance.
Not very helpful with the intel chips because of 'shared memory'.
Recommendation: set
(default = set)
h. "fixed"
disable mode switching.
Recommendation: do not set
(default = not set)
The binary parameters can be unset with a "no" prefix, example "noaccel".
The default parameter (not named) is the mode.
C. Kernel booting
Separate each option/option-pair by commas (,) and the option from its value
with an equals sign (=) as in the following:
Sample Usage
In /etc/lilo.conf, add the line:
This will initialize the framebuffer to 800x600 at 32bpp and 75Hz. The
framebuffer will use 8 MB of System RAM. hw acceleration of text and cursor
will be enabled.
D. Module options
The module parameters are essentially similar to the kernel
parameters. The main difference is that you need to include a Boolean value
(1 for TRUE, and 0 for FALSE) for those options which don't need a value.
Example, to enable MTRR, include "mtrr=1".
Sample Usage
Using the same setup as described above, load the module like this:
modprobe intelfb mode=800x600-32@75 vram=8 accel=1 hwcursor=1
Or just add the following to /etc/modprobe.conf
options intelfb mode=800x600-32@75 vram=8 accel=1 hwcursor=1
and just do a
modprobe intelfb
E. Acknowledgment:
1. Geert Uytterhoeven - his excellent howto and the virtual
framebuffer driver code made this possible.
2. Jeff Hartmann for his agpgart code.
3. David Dawes for his original kernel 2.4 code.
4. The X developers. Insights were provided just by reading the
XFree86 source code.
5. Antonino A. Daplas for his inspiring i810fb driver.
6. Andrew Morton for his kernel patches maintenance.
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