On Mon, 27 Aug 2001 18:28:19 +0100, Philip Blundell <philb@gnu.org> wrote:
>
> >In the long run I think you're right, but I was trying to deal with
> >the fact that the parport ECP mode doesn't work unless DMA is used.
>
> Can you be more specific about what goes wrong with it? In theory
> it should be possible to negotiate into (and use!) ECP mode on any
> port -- if hardware assistance isn't available, parport will
> perform ECP protocol in software. From the lp point of view using
> software-ECP is probably a bad thing for performance, but it should
> still work the same and I think we should retain the ability for
> drivers to do this if they want to, say if some particular
> peripheral functionality is only available in ECP mode.
>
The problem I was having with software-ECP was that I was getting
garbage data at the printer. I never figured out if it was missing,
extra, or just garbled data because the problem went away once
I compiled with FIFO/DMA support.
> Having thought about it some more, I'm now convinced that
> parport_pc should only set bits in port->modes when a particular
> mode is both supported by the underlying hardware and available in
> this configuration. It sounds like there might still be other
> bugs, but that should be enough to make your particular problem go
> away. Could you produce a patch to do that, plus a modified
> version of your lp.c change?
>
> p.
>
Yes, I can do that.
-- Dave Strauss
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