Re: [PATCH/RFC] PCI prepare/activate instead of enable to avoid IRQ storm and rogue DMA access

Russell King
2007-03-14T22:58:18Z

On Wed, Mar 14, 2007 at 06:34:11PM -0400, Jeff Garzik wrote:
> Russell King wrote:
> >pci_enable_device() doesn't deal with this; in most PCI setups I've
> >seen, there is no control at PCI level over whether a device generates
> >an interrupt on the bus. Certainly the memory and io command enables
>
> PCI grew an interrupt enable while you weren't looking:
> PCI_COMMAND_INTX_DISABLE

That's fine for devices which conform to the later PCI specs, but not
all do.

> It was added in PCI 2.3 I think.

Correct.

> Older PCI devices certainly do not have this standardized bit.

No PCI device that I have has that bit - including the raid card I
bought last year...

In any case, relying on such a new control bit to implement this kind
of functionality would result in a very hit and miss result; Linux
tends to get used on things other than the bleeding edge of hardware
technology.

--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/