Re: change MSI/MSI-X APIs

[David Laight <david%l8s.co.uk@localhost>]

On Mon, May 11, 2015 at 03:15:25PM +0900, Kengo NAKAHARA wrote:
> Hi,
> 
> I received feedback from some device driver authors. They point out
> establish, disestablish and release APIs should be unified for INTx,
> MSI and MSI-X. So, I would change the APIs as below:

Some more feedback...

PCIe devices that only support MSI-X could have support for very
large numbers of interrupts.

Some might only be needed if a specific function is used,
or might only be used to load sharing (eg multi-q ethernet).
In either case you might want to allocate some of the MSI-X
vectors at driver load time, and allocate others at a much later
time.
IIRC nothing in the hardware spec stops you doing this.

Theoretically you could allocate the MSI-X vector (etc)
when the interrupt is enabled, and dealloacate on disable
(apart from timing problems on the hardware).
I'm not suggesting you go that far!

This would also make it less likely that interrupts won't
be available for drivers that initialise later on.

	David

-- 
David Laight: david%l8s.co.uk@localhost