On Tue, Jan 26, 2016 at 04:48:25PM +0100, Thomas Gleixner wrote: > On Tue, 26 Jan 2016, Bjorn Helgaas wrote: > > On Tue, Jan 26, 2016 at 09:26:29AM +0100, Thomas Gleixner wrote: > > > The proper solution here is to flag that this device does not have an > > > interrupt connected and act accordingly in the device driver, i.e. do not call > > > request_irq() in the first place. > > > > This is the crux of the problem. As far as I know, PCI doesn't have > > a flag to indicate that dev->irq is a wire that's not connected, so > > there's no generic way for a driver to know whether it should call > > request_irq(). > > Ok. > > > We could add one, of course, but that only helps in the drivers we > > update. It'd be nice if we could figure out a way to fix this > > without having to touch all the drivers. > > Hmm. > > > I think any driver that uses line-based interrupts can potentially > > fail if the platform uses Interrupt Line == 255 to indicate that the > > line is not connected. If another driver happens to be using IRQ 255, > > request_irq() may fail as it does here. Otherwise, I suspect > > request_irq() will return success, but the driver won't get any > > interrupts. > > Right. So we could certainly do something like this INVALID_IRQ thingy, but > that looks a bit weird. What would request_irq() return? > > If it returns success, then drivers might make the wrong decision. If it > returns an error code, then the i801 one works, but we might have to fix > others anyway. I was thinking request_irq() could return -EINVAL if the caller passed INVALID_IRQ. That should tell drivers that this interrupt won't work. We'd be making request_irq() return -EINVAL in some cases where it currently returns success. But even though it returns success today, I don't think the driver is getting interrupts, because the wire isn't connected. > I think it's better to have a software flag in pci_dev to indicate that there > is no irq line and fix up the (probably few) affected drivers so they avoid > calling request_irq() and take the right action. We could add an "irq_valid" flag in struct pci_dev and make a new rule that drivers should check dev->irq_valid before using dev->irq. But realistically, i801 is the only place that will check irq_valid because that's the only driver where we know about a problem, so that seems like sort of a point solution. Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
