X Windows Porting and Questions

kyle.unice at L-3com.com kyle.unice at L-3com.com
Fri Dec 19 10:00:13 PST 2008

We are putting X Windows on an embedded platform with a touch screen.
The embedded platform has a 300Mhz CPU so we are working on ways to
improve performance.  We have written a framebuffer driver for the LCD.
We understand that X Windows maps the video memory into userspace and
then modifies the userspace memory with the images for the screen.  As
it is we have to use a shadow buffer in our driver and move out the
pixel information to the LCD.  It would be nice if X Windows would tell
us (via an ioctl or something) which rectangle(s) in the screen have
changed.  As it is now we have to write the entire buffer every time to
the LCD.   We need to know where in the X Windows code this framebuffer
is modified so we can add code to tell our driver exactly what
rectangle(s) have changed.

Also we are using Linux 2.6.10 and X Windows 6.8.  The touch screen
support in 6.8 is not finished we know.  Currently we are using the
tslibdev.c touchscreen driver but can't get it to track well  to the LCD
(yes we did calibrate it).  Any suggestions on how to get a touch screen
to work with 6.8 would be helpful also.


Kyle Unice 
L-3 Communications / Communication Systems - West 
Senior Staff Engineer - Rapid Product Development 
322 North 2200 West Dock 3 MS F1J12 
Salt Lake City, UT  84116-2988 
Voice: (801) 594-2687 
Fax: (801) 594-2980 

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