Hello,
I've been deferring a problem I ran into a few months back and I
figure a new year is a good time to readdress it.
I have a loadable module that controls some hardware. Within this
hardware are various bits that need to be strobed (i.e set for a
minimum specified time and then reset). I have several ioctl()
functions set to do this, but when I tried using a usleep() to force
a minimum delay, the system hanged. I did a work around by using the
CPU internal register timer rdtscl(), but this has the side effect of
tying up the CPU instead of allowing a reschedule as (hopefully) a
usleep() would do.
An example of what I'd like to do is:
...
case STROBE_RESET:
{
hwRegister |= RESET_MASK;
usleep (10000L); // hold bit high for at least 10ms
hwRegister &= ~RESET_MASK;
break;
}
...
Some delays are shorter (i.e. 20us).
What (if any) taboos exist for using sleep() in a kernel ioctl call
and what alternatives exist?
Kernel is 2.6.13 w/preemption, soon to be moving to a later version,
Thanks,
-Bruce
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