ncr53c8xx + tulip IRQ sharing

Jon Lewis (jlewis@inorganic5.fdt.net)
Sun, 15 Feb 1998 13:15:44 -0500 (EST)

I've got a couple of brain damaged AIR P90 boards that won't let me assign
IRQ's to individual PCI slots. When I use multiple NCR SCSI cards,
sharing IRQs between them isn't a problem. When I recently tried
upgrading from an ISA ethernet card to a PCI (SMC 8432), the ethernet card
wanted to share with the SCSI cards, and ethernet did not work.

I found in one of Don Becker's web pages the following:

---
My other PCI board always uses the same IRQ as an Adaptec 2940 


The preferred solution is to put each device on its own IRQ line. But some
motherboards, notably the Intel PR440FX, don't permit this. To use both at
the same time requires a slight modification of the 2940 driver: remove
the SA_INTERRUPT flag to the request_irq() call. This is required whenever
the 2940 driver must share an IRQ with any other device driver.


-     if (request_irq(config->irq, aic7xxx_isr, SA_INTERRUPT | SA_SHIRQ,
+     if (request_irq(config->irq, aic7xxx_isr, SA_SHIRQ, "aic7xxx",NULL))

---


I notice the NCR driver does the same thing (use of SA_INTERRUPT |
SA_SHIRQ)...so is it safe to apply the same sort of patch to the NCR
driver...removing SA_INTERRUPT?  Does doing so introduce any sorts of
performance or stability problems? 


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