Re: [PARPORT] ppdev ECP addr ops

Tim Waugh (
Mon, 26 Jul 1999 19:56:21 +0100 (GMT)

On Mon, 26 Jul 1999, Thomas Sailer wrote:

> - hardware EPP: works
> - software emul EPP: the program hanged forever or until a PTRACE
> attach,
> in which case it immediately returned (having no bytes transmitted).
> - hardware ECP: ecp_write_addr works, ecp_read_data returned
> immediately, having
> no bytes read
> - software ECP: same as hw ECP
> will investigate further some time.

Hmm. I'll take a look at the code. The sw EPP case looks very weird.

> Under 2.2.10 with the ppdev1 patch, I somehow managed (using
> strace and ctrl-c) to make ppdev or the kernel forget to unregister port
> and to decrement ppdev use count, but don't ask me how I did that...

!! There are other bugs in ppdev1; I've released ppdev2, and it should
play nicely with control lines and interrupts now. Also please note that
select now has no side effects -- you must use another ioctl to clear the
interrupt count.

> Another issue: the parport probing routines play games with
> parport_pc_ops, replacing method pointers there, and then a reference
> to parport_pc_ops is stored in parport->ops. Doesn't that mean that
> all PC parports share the same method table? That does only work if
> all ports have the same hw capabilities...

You've got me there, yes. I should have given that more thought.
Patches welcome, or else I'll do it myself when I get a moment.


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This archive was generated by hypermail 2.0b3 on Mon 26 Jul 1999 - 15:26:46 EDT