Re: [PATCH 1/4] media: subdev: Add checks for subdev features

[Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>]

On 04/04/2024 14:09, Sakari Ailus wrote:
> Moi,
> 
> On Thu, Apr 04, 2024 at 01:50:00PM +0300, Tomi Valkeinen wrote:
>> Add some checks to verify that the subdev driver implements required
>> features.
>>
>> A subdevice that supports streams (V4L2_SUBDEV_FL_STREAMS) must do one
>> of the following:
>>
>> - Implement neither .enable/disable_streams() nor .s_stream(), if the
>>    subdev is part of a video driver that uses an internal method to
>>    enable the subdev.
>> - Implement only .enable/disable_streams(), if support for legacy
>>    sink-side subdevices is not needed.
>> - Implement .enable/disable_streams() and .s_stream(), if support for
>>    legacy sink-side subdevices is needed.
>>
>> At the moment the framework doesn't check this requirement. Add the
>> check.
>>
>> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
>> ---
>>   drivers/media/v4l2-core/v4l2-subdev.c | 27 +++++++++++++++++++++++++++
>>   1 file changed, 27 insertions(+)
>>
>> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
>> index 4c6198c48dd6..b90b5185e87f 100644
>> --- a/drivers/media/v4l2-core/v4l2-subdev.c
>> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
>> @@ -1519,6 +1519,33 @@ int __v4l2_subdev_init_finalize(struct v4l2_subdev *sd, const char *name,
>>   				struct lock_class_key *key)
>>   {
>>   	struct v4l2_subdev_state *state;
>> +	struct device *dev = sd->dev;
>> +	bool has_disable_streams;
>> +	bool has_enable_streams;
>> +	bool has_s_stream;
>> +
>> +	/* Check that the subdevice implements the required features */
>> +
>> +	has_s_stream = sd->ops && sd->ops->video && sd->ops->video->s_stream;
>> +	has_enable_streams = sd->ops && sd->ops->pad && sd->ops->pad->enable_streams;
>> +	has_disable_streams = sd->ops && sd->ops->pad && sd->ops->pad->disable_streams;
> 
> There is v4l2_subdev_has_op(). Please also run:
> 
> 	./scripts/checkpatch.pl --strict --max-line-length=80
> 
> on this.
> 
>> +
>> +	if (has_enable_streams != has_disable_streams) {
>> +		dev_err(dev,
>> +			"subdev '%s' must implement both or neither of .enable_streams() and .disable_streams()\n",
>> +			sd->name);
>> +		return -EINVAL;
>> +	}
>> +
>> +	if (sd->flags & V4L2_SUBDEV_FL_STREAMS) {
>> +		if (has_s_stream && !has_enable_streams) {
> 
> Is the s_stream callback allowed to be something else than NULL or
> v4l2_subdev_s_stream_helper?

v4l2_subdev_s_stream_helper() only supports subdevs with a single source 
pad. The driver can implement its own version.

  Tomi