ppc irq handling vs. sym53c500_cs driver

Bob Tracy rct at gherkin.frus.com
Wed Oct 27 13:37:17 EDT 2004

I'm the current author/maintainer of the sym53c500_cs driver for 2.6
and later kernels, and the other user of the New Media Bus Toaster
(PCMCIA SCSI card, circa 1997) made contact a few days ago :-).  He's
trying to use the sym53c500_cs driver on a Mac G4 Powerbook (ppc
architecture), and failing...  The problem seems to be something
associated with the request_irq() implementation on ppc machines.
Card Services is attempting to assign the card the same IRQ as his
yenta controller, which isn't necessarily a problem except request_irq()
on ppc will fail unless both drivers agree to share the interrupt.
Anyway, for Guiseppe, the request_irq() call fails, and the sym53c500_cs
driver exits.

The nsp_cs.c PCMCIA SCSI driver seems to avoid the issue entirely by
doing something like "link->irq.Handler = &nspintr;".  Presumably, I
could do something similar in the sym53c500_cs driver, but I could
use some guidance as far as pros/cons of the two approaches.  I suspect
there's more to converting the sym53c500_cs driver to use the new
scheme than meets the eye.  For whatever it's worth, there's no
identified need for this driver to be usable on non-PCMCIA hardware,
so if the use of request_irq() is a relic associated with the non-Card
Services environment, that would be useful information.

Thanks in advance for comments/suggestions.

Bob Tracy                   WTO + WIPO = DMCA? http://www.anti-dmca.org
rct at frus.com

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