Messages in this thread | | | Date | Tue, 22 Apr 1997 00:44:17 +0100 (BST) | From | Philip Blundell <> | Subject | Re: parport patch / lp_readback |
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On Tue, 22 Apr 1997, Carsten Gross wrote:
> I think it is possible that the "acknowledge" line from the printer port > could be a problem. During normal printing every (beat me: it's > something with the rising or falling edge of the signal...) acknowledge > from the printer generates an interrupt. But the readback uses the > acknowledge line too and at the moment there is no code to handle the > interrupts during reading. Theoretically this is a problem, but I'm not > sure because a simple reprogramming of the control register disables the > interrupts. But I'm not able to test it, because I've the printer > interrupts disabled.
Oh, right. Yeah, we should be able to either suppress the interrupts or just set a flag so they're ignored. I don't think it's a big problem.
> Your other question about reading the status during writing: At the > moment of "reading" you are unable to write because the 'SelectIN' line > sets the printer offline. The same for writes: During a 'write' SelectIN > commands the printer to be "online". A 'read' operation not respecting > this would print at least an ascii NULL character. With a flag it is > possible to control this problem but it is (a little bit) sophisticated > and means changes distributed over the whole lp driver.
I thought that might be the case. Oh well. It can wait until this putative rewrite of lp happens then (which I'll do if nobody else volunteers).
p.
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