Messages in this thread | | | Date | Wed, 27 Mar 2024 13:06:42 +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 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)?
>>>>>>> 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.
Tomi
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