Re: [Intel-gfx] [PATCH 03/26] drm/irq: Ditch DRIVER_IRQ_SHARED

Emil Velikov
2019-01-28T11:47:23Z

On 2019/01/25, Daniel Vetter wrote:
> On Fri, Jan 25, 2019 at 02:46:55PM +0000, Emil Velikov wrote:
> > On Thu, 24 Jan 2019 at 16:58, Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> > >
> > > This is only used by drm_irq_install(), which is an optional helper.
> > > And the right choice is to set it for all pci devices, and not for
> > > everything else.
> > >
> > Can you please add some information (or reference) why it's the right choice?
>
> pci devices can have a shared interrupt line. That's definitely the case
> for legacy pci, and I guess carries over to pcie. msi/msi-x interrupts
> will give you dedicated interrupts, but it doesn't really hurt to mark
> them as shared.
>
> I guess I could rephrase to state:
>
> "This is only used by drm_irq_install(), which is an optional helper.
> For legacy pci devices this is required (due to interrupt sharing without
> msi/msi-x), and just making this the default exactly matches the behaviour
> of all existing drivers using the drm_irq_install() helpers. In case that
> ever becomes wrong drivers can roll their own irq handling, as many
> drivers already do (for other reasons like needing a threaded interrupt
> handler, or having an entire pile of different interrupt sources)."
>
> That better?

It's amazing. Thank you very much.

-Emil
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