[PATCH v2 2/2] powerpc/PCI: Disable MSI/MSI-X interrupts at PCI probe time in OF case

Guilherme G. Piccoli gpiccoli at linux.vnet.ibm.com
Tue Sep 8 09:04:22 AEST 2015

> On Sun, 2015-09-06 at 17:44 +0300, Michael S. Tsirkin wrote:

>>> My question is: is necessary to initialize MSI capabilities even with
>>> CONFIG_PCI_MSI not set? In negative case, would be "cleaner" revert the 3
>>> commits, right?

>> I think the reason why it's necessary is explained in
>> commit log for commit 1851617cd2da9cc53cdc1738f4148f4f042c0e56 (that's
>> [3] below).

Thanks very much Michael. I re-read the text of your commit, and makes 
sense then to initialize the MSI capabilities even with CONFIG_PCI_MSI 
not set.

> On 09/07/2015 12:17 AM, Michael Ellerman wrote:
> Well yes and no.
> What we want to do when CONFIG_PCI_MSI=n is disable MSI on the device. In order
> to do that the code first initialises dev->msi[x]_cap.
> But arguably that's wrong, ie. when CONFIG_PCI_MSI=n dev->msi[x]_cap *should*
> be zero so that any code which erroneously tries to use them will fail.
> But perhaps that's being too pedantic :)

I thought exactly this - that was the reason of my questioning. Thanks 
for your opinion Michael - I'd call the argument logical, not pedantic 


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