Re: [PATCH] pci: fix unavailable irq number 255 reported by BIOS

[Rafael J. Wysocki]

On Fri, Jan 22, 2016 at 8:23 PM, David Daney <ddaney.cavm@xxxxxxxxx> wrote:
> On 01/22/2016 09:53 AM, Bjorn Helgaas wrote:
>>
>> On Thu, Jan 21, 2016 at 11:58:26PM +0100, Rafael J. Wysocki wrote:
>>>
>>> On Thu, Jan 21, 2016 at 3:41 PM, Cao jin <caoj.fnst@xxxxxxxxxxxxxx>
>>> wrote:
>>>>
>>>> Hi,
>>>>
>>>>      IMHO, I think maybe modification on i801_smbus driver is easier.
>>>>
>>>>      Because when i801_smbus request_irq using pci_dev->irq, this
>>>> pci_dev->irq seems still holds the value read from register(
>>>> pci_setup_device->pci_read_irq), if the value is 255, it is invalid in
>>>> register,
>>>
>>>
>>> Right.
>>>
>>> Which is why the PCI core should not leak it into the driver's ->probe
>>> callback.
>>
>>
>> Is there a reserved IRQ value we could use to mean "invalid"?
>
>
> In many (most) cases, zero indicates no irq.

Zero is a valid timer IRQ on x86, though, so it's better not to give
any special meaning to it in general.

Using ~0 as suggested by Bjorn should work as it would cause
request_irq() to return -EINVAL if passed to it AFAICS.

Thanks,
Rafael