Re: [PATCH V5 2/2] virtio-gpio: Add support for interrupts

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Jul 19, 2021 at 03:54:11PM +0530, Viresh Kumar wrote:
> On 16-07-21, 13:09, Viresh Kumar wrote:
> > This patch adds support for interrupts to the virtio-gpio specification.
> > This uses the feature bit 0 for the same.
> 
> Michael (and other virtio experts),
> 
> I have a doubt about interrupt messages initiated by the device. There is
> nothing meaningful I want to return from the driver to the device on an
> interrupt event, but I need to make sure the device doesn't send another
> interrupt for the same GPIO line, before the previous one is serviced. I was
> thinking about sending some sort of response message for it, but am not sure how
> to implement it.

My suggestion is this: driver adds a buffer to tell device
it wants an interrupt. device uses the buffer to notify
driver of the interrupt event.


> Another way out to implement this, is by adding to the spec that on interrupt
> the device MUST mask the interrupt line on the GPIO before sending the event to
> the driver and this irq can be re-enabled only by the driver sending another
> request over the primary virtqueue (and not interrupt virtqueue).
> 
> What do you suggest ?

Well vqs fundamentally can cause spurious interrupts. First suggestion
is closer to how other devices do this.

> -- 
> viresh