Re: [PARPORT] Re: L68K: Amiga-Parport-driver

Andrea Arcangeli (
Sun, 30 Aug 1998 02:17:53 +0200 (CEST)

On Sat, 29 Aug 1998, Philip Blundell wrote:

>I wasn't thinking in terms of performance really. The current code is
>certainly extremely ugly and could do with being changed. Having thought
>about it more, Joerg's plan of having the lowlevel driver claim the interrupt
>and call a function pointer to pass it to the higher devices sounds like the
>way forward. Fortunately I don't think this will break the API seen by
>high-level devices, even at the binary level, so we can safely make the change
>during the 2.2 release cycle without upsetting people.

I think it' s better to implement it now instead of wait the middle of

>Basically the way it would work would be that all the irq handling gunk would
>come out of parport_share.c; the lowlevel driver would claim interrupts as
>necessary and just do (port->cad->irq_func)(...port->cad->private...) to pass
>the interrupt up.

That was my same thought reading the last email.

>>I can' t find the first email of this thread...
>The gist of it was that on some hardware you need to perform a specific
>acknowledge cycle when you handle an interrupt. (This is true up to a point
>on the PC, but in that case the code in kernel/irq.c handles it -- apparently
>on the Amiga it's a lot more visible to drivers.)

If the irq chip ack it' s more visible it' s a bug in the amiga port. If
it has to be more visible for some unknown reasons we must add a new arch
specific API to the kernel and #define it {} for every other port.

And I don' t understand how changing the parport irq handling code would
help workarounding this port bug (even if I agree for other reasons to
change the code).

>At the moment the lowlevel driver is pretty much out of the loop as far as
>interrupts are concerned and so this is rather tricky to handle.

I don' t understand this point due my English I think. And btw what does
it mean "as far as xxx is concerned" ;-)? I' d like to use it too ;-)).
>From my vocabulary I understand "as far as xxx is interested"... is this
true? (I don' t think...)

Andrea[s] Arcangeli

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