Summary: How do I activate a userspace program from an rtlinux kernel module quickly ? Hello, I've been reading this mailinglist for some time and have experimented with rtlinux a little. My main interest is in programming demos, which may be described as a sort of realtime multimedia productions, much like what unix people know as `eye-candy'. What I'd like to do is build a kernel module that activates a routine that will poll the vertical retrace register of an IBM VGA card, and when the retrace starts, the kernel module should activate a userspace process, the demo. Then the userspace process continues for some time, and when it's finished rendering a screenful, it gives control to the other processes running in the background. Then some time later the realtime clock should activate the vertical retrace polling routine again and everything starts all over again. One loop of this passes in 1/70th of a second, since the refresh frequency of the IBM VGA in the mode used is 70Hz. By this method the userspace process will be able to update the screen at every screen refresh, and is thereby able to produce fluent motion animation. If i just reschedule the userspace process and poll the vertical retrace register directly, other processes don't get any cpu power and some (network traffic handling &c) will timeout eventually. The 70 Hz frequency is too high to use linux's default timer functionality. I have experimented with an rtlinux kernelmodule which made the rtc run at 8192Hz, and activate the vertical retrace polling routine just before the actual retrace would occur (some 10% earlier). I haven't been able to make a fast `connection' with the userspace process though. In most examples on rtlinux and rtai that I could find, the userspace programs are not realtime. My questions now are the following: How do I wake up the userspace process easily? Do i have to modify the default linux scheduler? Is rtlinux of any use here, or is it impossible to reschedule processes this fast? Thanks in advance, -- Tijs van Bakel, <[EMAIL PROTECTED]> --- [rtl] --- To unsubscribe: echo "unsubscribe rtl" | mail [EMAIL PROTECTED] OR echo "unsubscribe rtl <Your_email>" | mail [EMAIL PROTECTED] ---- For more information on Real-Time Linux see: http://www.rtlinux.org/~rtlinux/
