Tim Waugh wrote:
> Not having exclusive access just means that another driver might
> possibly try talking to (another device on) the port. This is only
> really an issue for devices that won't work in daisy-chain
> configurations, even as the last device on the chain. In particular,
> if your device is going to be claiming the port and not releasing it
> for large amounts of time (thirty seconds, a minute, minutes, etc), it
> should probably claim the port exclusively.
I understand. I think lcd4linux should claim it exclusively, because it
does a lot of things with the control lines, which could have strange
effects on any other device.
But I want kind of a 'fallback', because a lot of users will not load
lp.o with the right options. I wnat to get exclusive access, If I can't
get it, I will print a big fat warning, and continue without exclusive
access. Is there a way to clear the EXCL flag (other than closing an
reopening the device?)
> You should alias 'parport_lowlevel' to parport_pc in modules.conf.
> When your driver opens the ppdev port, 'parport_lowlevel' will get
But how does lp.o load parport_pc?
> Did you enable 'PARPORT_LP_CONSOLE' when you configured your kernel?
> If so, lp can't be unloaded.
Thanks again! That's it!
> > I don't like c) because it's non-portable and not available on older
> > cpu's
> select() is portable, but you don't get a guaranteed maximum delay.
Hmmm, what was c)? Oh, looping on rdtsc.
I don't think that select() has microsecond resolution, I suppose it
will reschedule and therefore have at least a 10ms delay (which is far
too long). But I will have a look at the kernel code..
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This archive was generated by hypermail 2b29 : Thu Mar 15 2001 - 05:09:01 EST