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SubjectRe: [PATCH v3 9/9] media: subdev: Support single-stream case in v4l2_subdev_enable/disable_streams()
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On 11/04/2024 14:48, Umang Jain wrote:
> Hi Tomi,
>
> On 11/04/24 4:37 pm, Tomi Valkeinen wrote:
>> On 11/04/2024 14:02, Umang Jain wrote:
>>> Hi Tomi,
>>>
>>> On 10/04/24 6:05 pm, Tomi Valkeinen wrote:
>>>> At the moment the v4l2_subdev_enable/disable_streams() functions call
>>>> fallback helpers to handle the case where the subdev only implements
>>>> .s_stream(), and the main function handles the case where the subdev
>>>> implements streams (V4L2_SUBDEV_FL_STREAMS, which implies
>>>> .enable/disable_streams()).
>>>>
>>>> What is missing is support for subdevs which do not implement streams
>>>> support, but do implement .enable/disable_streams(). Example cases of
>>>> these subdevices are single-stream cameras, where using
>>>> .enable/disable_streams() is not required but helps us remove the users
>>>> of the legacy .s_stream(), and subdevices with multiple source pads
>>>> (but
>>>> single stream per pad), where .enable/disable_streams() allows the
>>>> subdevice to control the enable/disable state per pad.
>>>>
>>>> The two single-streams cases (.s_stream() and
>>>> .enable/disable_streams())
>>>> are very similar, and with small changes we can change the
>>>> v4l2_subdev_enable/disable_streams() functions to support all three
>>>> cases, without needing separate fallback functions.
>>>>
>>>> A few potentially problematic details, though:
>>>
>>> Does this mean the patch needs to be worked upon more ?
>>
>> I don't see the two issues below as blockers.
>>
>>> I quickly tested the series by applying it locally with my use case
>>> of IMX283 .enable/disable streams and s_stream as the helper function
>>> and it seems I am still seeing the same behaviour as before (i.e. not
>>> being streamed) and have to carry the workaround as mentioned in [1]
>>> **NOTE**
>>
>> Ok... Then something bugs here, as it is supposed to fix the problem.
>> Can you trace the code a bit to see where it goes wrong?
>>
>> The execution should go to the "if (!(sd->flags &
>> V4L2_SUBDEV_FL_STREAMS))" blocks in v4l2_subdev_collect_streams() and
>> v4l2_subdev_set_streams_enabled(),
>
> The execution is not reaching in v4l2_subdev_collect streams() even, it
> returns at
>
>     if (!streams_mask)
>                 return 0;
>
> in v4l2_subdev_enable_streams()
>
> Refer to : https://paste.debian.net/1313760/
>
> My tree is based on v6.8 currently, but the series applies cleanly, so I
> have not introduced any  rebase artifacts. If you think, v6.8 might be
> causing issues, I'll then try to test on RPi 5 with the latest media
> tree perhaps.

So who is calling the v4l2_subdev_enable_streams? I presume it comes
from v4l2_subdev_s_stream_helper(), in other words the sink side in your
pipeline is using legacy s_stream?

Indeed, that helper still needs work. It needs to detect if there's no
routing, and use the implicit stream 0. I missed that one.

Tomi


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