Re: pci_enable_msi() for everyone?

[Grant Grundler]

On Fri, Jun 03, 2005 at 03:45:51PM -0700, Greg KH wrote:
> In talking with a few people about the MSI kernel code, they asked why
> we can't just do the pci_enable_msi() call for every pci device in the
> system (at somewhere like pci_enable_device() time or so).  That would
> let all drivers and devices get the MSI functionality without changing
> their code, and probably make the api a whole lot simpler.

One complication is some drivers will want to register a different
IRQ handler depending on if MSI is enabled or not.
If MSI is enabled (and usable), then some MMIO reads can be omitted.
I've posted a patch for tg3 driver:
	ftp://ftp.parisc-linux.org/patches/diff-2.6.10-tg3_MSI-03

(Just an example! It was not accepted because of buggy HW
 though it worked great on the HW I have access to.)

drivers/infiniband/hw/mthca driver is another example.

> Now I know the e1000 driver would have to specifically disable MSI for
> some of their broken versions, and possibly some other drivers might
> need this, but the downside seems quite small.
> 
> Or am I missing something pretty obvious here?

How can the driver know which IRQ handlers to register?

grant
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