[PATCH] intelfb documentation

Add a small documentation of the driver parameters.

Signed-off-by: Sylvain Meyer <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

Documentation/fb/intelfb.txt

···
+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:
+
+video=i810fb:option1,option2=value2
+
+Sample Usage
+------------
+
+In /etc/lilo.conf, add the line:
+
+append="video=intelfb:800x600-32@75,accel,hwcursor,vram=8"
+
+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.
+
+###########################
+Sylvain