Re: [PATCH] media: intel/ipu6: Set the VC of the stream as the SOF event id

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

On Mon, Nov 04, 2024 at 07:56:51AM +0000, Sakari Ailus wrote:
> On Mon, Nov 04, 2024 at 03:07:58AM +0000, Wang, Hongju wrote:
> > On Thursday, October 24, 2024 6:31 PM, Sakari Ailus wrote:
> > > On Thu, Oct 24, 2024 at 11:22:01AM +0800, Hongju Wang wrote:
> > > > In the virtual channel case, they should use v4l2_event.id to
> > > > distinguish SOF events of different streams. Therefore, we set the
> > > > virtual channel number of the stream as the SOF event ID. This number is unique.
> > > >
> > > > Signed-off-by: Hongju Wang <hongju.wang@intel.com>
> > > > ---
> > > >  drivers/media/pci/intel/ipu6/ipu6-isys-csi2.c | 1 +
> > > >  1 file changed, 1 insertion(+)
> > > >
> > > > diff --git a/drivers/media/pci/intel/ipu6/ipu6-isys-csi2.c
> > > > b/drivers/media/pci/intel/ipu6/ipu6-isys-csi2.c
> > > > index 051898ce53f4..5ad426afa0f0 100644
> > > > --- a/drivers/media/pci/intel/ipu6/ipu6-isys-csi2.c
> > > > +++ b/drivers/media/pci/intel/ipu6/ipu6-isys-csi2.c
> > > > @@ -578,6 +578,7 @@ void ipu6_isys_csi2_sof_event_by_stream(struct ipu6_isys_stream *stream)
> > > >  		.type = V4L2_EVENT_FRAME_SYNC,
> > > >  	};
> > > >
> > > > +	ev.id = stream->vc;
> > > >  	ev.u.frame_sync.frame_sequence = atomic_fetch_inc(&stream->sequence);
> > > >  	v4l2_event_queue(vdev, &ev);
> > > >
> > > 
> > > The id field in struct v4l2_event isn't used for the FRAME_SYNC event and
> > > also the virtual channel isn't communicated to the user space currently.
> > 	
> >   How to use the id field? User space should use SOF to do FRAME_SYNC,
> >   but the v4l2_event doesn't distinguish different streams. Do you have
> >   any good suggestions?
> 
> Ah, now I think I do understand the problem. The events are produced by the
> CSI-2 receiver sub-device but there are multiple streams and the event
> isn't stream-aware?
> 
> It's nice that the id field of the FRAME_SYNC event isn't in use for any
> other purpose. This should be taken into account in event subscription,
> too.
> 
> I'll add a patch documenting this in the metadata series. Any thoughts?

I think we could use the id field for this purpose, but maybe not to
report the VC. Userspace isn't VC-aware, we should instead convert the
VC to a stream.

> Cc Laurent and Hans.

-- 
Regards,

Laurent Pinchart