[libcamera-devel] [PATCH 1/5] libcamera: media_device: Provide the default entity

[Kieran Bingham]

Hi Laurent,

On 08/02/2019 15:44, Laurent Pinchart wrote:
> Hello,
> 
> On Thu, Feb 07, 2019 at 11:06:20PM +0100, Jacopo Mondi wrote:
>> Hi Kieran,
>>     ignorant question, is FL_DEFAULT an UVC specific thing?
> 
> It isn't, but it isn't widely used either. It would thus be fine using
> the default entity in UVC-specific tests or in the UVC pipeline handler,
> but not in the rest of the code, at least not without a fallback.

The only places that use this helper are the uvcvideo pipeline, and the
V4L2DeviceTest which is currently coded to skip if not operated on a UVC
device...

When this stops being coded to a UVC device - the helper can be removed
or updated as necessary.


>> A quick grep on kernel sources returns:
>>
>> $ git grep FL_DEFAULT drivers/media/
>> drivers/media/platform/omap3isp/ispresizer.c:   res->video_out.video.entity.flags |= MEDIA_ENT_FL_DEFAULT;
>> drivers/media/usb/uvc/uvc_entity.c:             entity->vdev->entity.flags |= MEDIA_ENT_FL_DEFAULT;
>>
>> So I guess not, as omap3 seems also omap3 uses that as well.
>>
>> If that's not a UVC specificity, I welcome this change.
>>
>> On Thu, Feb 07, 2019 at 09:21:15PM +0000, Kieran Bingham wrote:
>>> Add a helper to identify the default entity from a media device.
>>>
>>> Utilise it in the two places which iterate the entities manually, to allocated
>>> a V4L2Device from the default entity.
>>>
>>> Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
>>> ---
>>>  src/libcamera/include/media_device.h  |  1 +
>>>  src/libcamera/media_device.cpp        | 15 +++++++++++++++
>>>  src/libcamera/pipeline/uvcvideo.cpp   | 10 ++++------
>>>  test/v4l2_device/v4l2_device_test.cpp | 12 +++++-------
>>>  4 files changed, 25 insertions(+), 13 deletions(-)
>>>
>>> diff --git a/src/libcamera/include/media_device.h b/src/libcamera/include/media_device.h
>>> index 9f038093b2b2..361e8f4a4b86 100644
>>> --- a/src/libcamera/include/media_device.h
>>> +++ b/src/libcamera/include/media_device.h
>>> @@ -42,6 +42,7 @@ public:
>>>
>>>  	const std::vector<MediaEntity *> &entities() const { return entities_; }
>>>  	MediaEntity *getEntityByName(const std::string &name) const;
>>> +	MediaEntity *defaultEntity() const;
> 
> This should take an entity type as a parameter as the default flag is
> defined as "Default entity for its type". It could also be used, for
> instance, to discover the default camera sensor.

I don't understand how that would be implemented.

What extra item does it then check against? the entity type?


>>>  	MediaLink *link(const std::string &sourceName, unsigned int sourceIdx,
>>>  			const std::string &sinkName, unsigned int sinkIdx);
>>> diff --git a/src/libcamera/media_device.cpp b/src/libcamera/media_device.cpp
>>> index 800ed330fe6d..4af90e1590a1 100644
>>> --- a/src/libcamera/media_device.cpp
>>> +++ b/src/libcamera/media_device.cpp
>>> @@ -319,6 +319,21 @@ MediaEntity *MediaDevice::getEntityByName(const std::string &name) const
>>>  	return nullptr;
>>>  }
>>>
>>> +/**
>>> + * \brief Return the default MediaEntity within a MediaDevice
>>> + * \return The default entity if specified, or a nullptr otherwise
>>> + */
>>> +MediaEntity *MediaDevice::defaultEntity() const
>>> +{
>>> +	for (MediaEntity *entity : entities_) {
>>> +		if (entity->flags() & MEDIA_ENT_FL_DEFAULT) {
>>> +			return entity;
>>> +		}
>>
>> You could drop the inner braces { } here
>>> +	}
>>> +
>>> +	return nullptr;
>>> +}
>>> +
>>>  /**
>>>   * \brief Retrieve the MediaLink connecting two pads, identified by entity
>>>   * names and pad indexes
>>> diff --git a/src/libcamera/pipeline/uvcvideo.cpp b/src/libcamera/pipeline/uvcvideo.cpp
>>> index fc31c52c0ecd..ed8228bb2fc6 100644
>>> --- a/src/libcamera/pipeline/uvcvideo.cpp
>>> +++ b/src/libcamera/pipeline/uvcvideo.cpp
>>> @@ -146,13 +146,11 @@ bool PipelineHandlerUVC::match(DeviceEnumerator *enumerator)
>>>
>>>  	media_->acquire();
>>>
>>> -	for (MediaEntity *entity : media_->entities()) {
>>> -		if (entity->flags() & MEDIA_ENT_FL_DEFAULT) {
>>> -			video_ = new V4L2Device(entity);
>>> -			break;
>>> -		}
>>> -	}
>>> +	MediaEntity *entity = media_->defaultEntity();
>>> +	if (!entity)
>>
>> Looking at existing code if you don't find any DEFAULT entity, you
>> return false as you do here, but also release the media device.
>>
>> Should the same be done here?
> 
> I think it should, and a message should likely be logged too.

Ack.


> 
>>> +		return false;
>>>
>>> +	video_ = new V4L2Device(entity);
>>>  	if (!video_ || video_->open()) {
>>>  		if (!video_)
>>>  			LOG(UVC, Error) << "Could not find a default video device";
>>> diff --git a/test/v4l2_device/v4l2_device_test.cpp b/test/v4l2_device/v4l2_device_test.cpp
>>> index 18d014caf4c8..dd28cccada6b 100644
>>> --- a/test/v4l2_device/v4l2_device_test.cpp
>>> +++ b/test/v4l2_device/v4l2_device_test.cpp
>>> @@ -46,15 +46,13 @@ int V4L2DeviceTest::init()
>>>
>>>  	media_->acquire();
>>>
>>> -	for (MediaEntity *entity : media_->entities()) {
>>> -		if (entity->flags() & MEDIA_ENT_FL_DEFAULT) {
>>> -			dev_ = new V4L2Device(entity);
>>> -			break;
>>> -		}
>>> -	}
>>> +	MediaEntity *entity = media_->defaultEntity();
>>> +	if (!entity)
>>> +		return TestFail;
> 
> Note that we're planning to use vivid instead of uvcvideo for V4L2Device
> tests, so this may not be a good idea.


Ok - so that should change at that point. Here to me it's a failure,
because we will not know which UVC device to check against.

I can add a comment to say that this check is UVC specific.



>>> +	dev_ = new V4L2Device(entity);
>>>  	if (!dev_)
>>> -		return TestSkip;
>>> +		return TestFail;
>>>
>>>  	return dev_->open();
>>>  }
> 

-- 
Regards
--
Kieran