Messages in this thread | | | Date | Wed, 3 Apr 2024 12:25:44 +0300 | Subject | Re: [PATCH] media: v4l2-subdev: Support enable/disable_streams for single-pad subdevs | From | Tomi Valkeinen <> |
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On 02/04/2024 15:05, Sakari Ailus wrote: > On Wed, Mar 27, 2024 at 03:39:31PM +0200, Tomi Valkeinen wrote: >> 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. > > If there are is no support for routing, isn't streaming either enabled or > disabled on all of them?
Hmm, no, I don't see why that would be the case. If a subdev has two source pads, and it gets an enable_streams() call on the first source pad, why would the second source pad be enabled too?
Tomi
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