Re: Machine wedges solid after one serial-port source-lineaddition...

• Previous message: Barry Bouwsma: "Kernel module problems/questions"
• In reply to: Terry Lambert: "Re: Machine wedges solid after one serial-port source-lineaddition..."
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Date: Wed, 24 Sep 2003 18:34:11 +0200 (CEST)
To: FreeBSD List of Hackers <hackers@freebsd.org>

[Drop hostname part of IPv6-only address above to obtain IPv4-capable e-mail,
 or just drop me from the recipients and I'll catch up from the archives]

Terry Lambert writes:

> I remember wakeup() being bad. Taking any time to do anything
> at all more than just queueing data and going away is probably
> bad.

Then that's probably why it worked fine for some hours, then failed
miserably. Thanks!

> If it were my project, I'd mirror the values out to a status
> structure that's only written at interrupt, and read and reset
> at software interrupt, and then use the soft interrupt handler
> to raise the signals/send the wakeup/whatever and then resets
> the flags bits to zero via a call down that synchronizes like

Maybe I'll turn back to this, when I'm older and wiser. But also, serial
ports are a scarcity for me, so I'm wondering what else I can use to get
precise timing information, to free up the serial port for something else.

I wrote earlier (from an invalid address that probably most list readers
rejected as spam) that I had a problem accessing the parallel port nACK
as /dev/pps for the precise timing already present in the kernel source,
and simultaneously as /dev/ppi for coarse timing via polling from which
I'd determine the time that the PPS signal refers to.

I tried adding printf()s to various parallel-port kernel code to see if
there might be an interrupt I could jump onto for each transition of
the nACK status line, but I suspect my lack of success with both swings
of the signal has to do with not doing it right.

So I'll ask a basic question here, forgive my ignorance: Can the lines
of the parallel port be used to generate interrupts that I can use, in
the same way that I've been able to use the four serial port status
lines, or is this right out?

And another question, I see three unused joystick connectors on the three
sound cards in my machine, that are less likely to be used than the so-far-
unused parallel port.

Would it be possible to get interrupts from the sound card's joystick
connector, when interfaced with suitable hardware to the radio clock
output, that I would also theoretically be able to use? Or is this also
something I'd need to poll the status of the switch(es), so only coarse
precision would be possible?

Please excuse my basic ignorance of fundamental PC hardware principles,
and I'll welcome pointers to sources of more knowledge.

Thanks,
Barry Bouwsma

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• Previous message: Barry Bouwsma: "Kernel module problems/questions"
• In reply to: Terry Lambert: "Re: Machine wedges solid after one serial-port source-lineaddition..."
• Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]