Messages in this thread | | | Date | Wed, 27 Mar 2024 15:39:31 +0200 | Subject | Re: [PATCH] media: v4l2-subdev: Support enable/disable_streams for single-pad subdevs | From | Tomi Valkeinen <> |
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On 27/03/2024 15:32, Sakari Ailus wrote: > Heissulivei, > > On Wed, Mar 27, 2024 at 01:06:42PM +0200, Tomi Valkeinen wrote: >> On 27/03/2024 12:46, Sakari Ailus wrote: >>> Heippa, >>> >>> On Mon, Mar 25, 2024 at 07:56:46PM +0200, Tomi Valkeinen wrote: >>>> On 25/03/2024 19:52, Sakari Ailus wrote: >>>>> Moi, >>>>> >>>>> On Mon, Mar 25, 2024 at 03:43:01PM +0200, Tomi Valkeinen wrote: >>>>>> On 25/03/2024 15:02, Sakari Ailus wrote: >>>>>>> Moi, >>>>>>> >>>>>>> Thanks for the patch. >>>>>>> >>>>>>> On Mon, Mar 25, 2024 at 02:50:55PM +0200, Laurent Pinchart wrote: >>>>>>>> Hi Tomi, >>>>>>>> >>>>>>>> On Mon, Mar 25, 2024 at 02:43:23PM +0200, Tomi Valkeinen wrote: >>>>>>>>> Currently a subdevice with a single pad, e.g. a sensor subdevice, must >>>>>>>>> use the v4l2_subdev_video_ops.s_stream op, instead of >>>>>>>>> v4l2_subdev_pad_ops.enable/disable_streams. This is because the >>>>>>>>> enable/disable_streams machinery requires a routing table which a subdev >>>>>>>>> cannot have with a single pad. >>>>>>>>> >>>>>>>>> Implement enable/disable_streams support for these single-pad subdevices >>>>>>>>> by assuming an implicit stream 0 when the subdevice has only one pad. >>>>>>>>> >>>>>>>>> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com> >>>>>>>>> --- >>>>>>>>> Even though I did send this patch, I'm not sure if this is necessary. >>>>>>>>> s_stream works fine for the subdevs with a single pad. With the upcoming >>>>>>>>> internal pads, adding an internal pad to the subdev will create a >>>>>>>>> routing table, and enable/disable_streams would get "fixed" that way. >>>>>>> >>>>>>> I'd like to get rid of a redundant way to control streaming. >>>>>> >>>>>> We can't get rid of it anyway, can we? We're not going to convert old >>>>>> drivers to streams. >>>>> >>>>> I'd expect to do that but it'd take a long time. That being said, I think >>>>> we need to consider devices without pads (VCMs) so it may well be this >>>>> would remain after all. >>>>> >>>>>> >>>>>> For new drivers, yes, we shouldn't use s_stream. But is the answer for new >>>>>> sensor drivers this patch, or requiring an internal pad? >>>>> >>>>> For new drivers I'd like to see an internal pad in fact. >>>>> {enable,disable}_streams is still internal to the kernel. >>>> >>>> So, you think this patch should be dropped? >>> >>> No, no. Not all sub-device drivers with pads are camera sensor drivers. :-) >> >> Hmm, alright. So we want to support enable/disable_streams for sub-devices >> with multiple source pads but no routing (so probably no sink pads)? > > That should be allowed indeed, in order to move from s_stream() to > {enable,disable}_streams(). > >> >>>>>>>>> So perhaps the question is, do we want to support single-pad subdevs in >>>>>>>>> the future, in which case something like this patch is necessary, or >>>>>>>>> will all modern source subdev drivers have internal pads, in which >>>>>>>>> case this is not needed... >>>>>>>> >>>>>>>> I think the latter would be best. I however can't guarantee we won't >>>>>>>> have valid use cases for (enable|disable)_streams on single-pad subdevs >>>>>>>> though, so you patch could still be interesting. >>>>>>> >>>>>>> Instead of the number of pads, could we use instead the >>>>>>> V4L2_SUBDEV_FL_STREAMS flag or whether g_routing op is supported to >>>>>>> determine the need for this? >>>>>> >>>>>> Maybe, but are they better? Do you see some issue with checking for the >>>>>> number of pads? I considered a few options, but then thought that the most >>>>>> safest test for this case is 1) one pad 2) enable/disable_streams >>>>>> implemented. >>>>> >>>>> I think I'd actually prefer {enable,disable}_streams in fact. >>>> >>>> Hmm, sorry, now I'm confused =). What do you mean with that? >>> >>> I'd use V4L2_SUBDEV_FL_STREAMS flag instead of the number of pads. The >>> number of pads is less related to routing. >> >> Well, with one pad you cannot have routing =). >> >> In this patch I used sd->enabled_streams to track the enabled streams, but >> if we need to support multiple pads, I'll have to invent something new for >> that. > > What exactly do you think needs to be changed? This is just about starting > and stopping streaming using a different sent of callbacks, right?
The helpers track which streams are enabled, so we need some place to store the enabled streams.
For V4L2_SUBDEV_FL_STREAMS we have that in state->stream_configs for each stream. For the one-source-pad case we have a subdev wide sd->enabled_streams to store that. But we don't have any place at the moment to store if a pad is enabled.
Tomi
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