[libcamera-devel] [PATCH v2 3/5] android: camera_device: Postpone mapped streams handling

[Umang Jain]

Hi Jacopo,

On 5/30/22 11:56, Jacopo Mondi via libcamera-devel wrote:
> Hi Paul
>
> On Fri, May 27, 2022 at 06:34:38PM +0900, Paul Elder wrote:
>> From: Jacopo Mondi <jacopo at jmondi.org>
>>
>> Mapped streams are generated by post-processing and always require a
>> source buffer from where to process image data from.
>>
>> In case a Mapped stream is requested but its source stream is not, it
>> is required to allocate a buffer on the fly and add it to the
>> libcamera::Request.
>>
>> Make sure a source stream is available for all mapped streams, and if
>> that's not the case, add a dedicated buffer to the request for that
>> purpose.
>>
>> Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
>> Signed-off-by: Paul Elder <paul.elder at ideasonboard.com>
>>
>> ---
>> Changes in v2:
>> - cosmetic changes in code
>> - fix typo in the commit message
>> ---
>>   src/android/camera_device.cpp | 80 +++++++++++++++++++++++++++++++----
>>   1 file changed, 72 insertions(+), 8 deletions(-)
>>
>> diff --git a/src/android/camera_device.cpp b/src/android/camera_device.cpp
>> index 20599665..95c14f60 100644
>> --- a/src/android/camera_device.cpp
>> +++ b/src/android/camera_device.cpp
>> @@ -9,6 +9,7 @@
>>
>>   #include <algorithm>
>>   #include <fstream>
>> +#include <set>
>>   #include <sys/mman.h>
>>   #include <unistd.h>
>>   #include <vector>
>> @@ -923,6 +924,32 @@ int CameraDevice::processCaptureRequest(camera3_capture_request_t *camera3Reques
>>   	LOG(HAL, Debug) << "Queueing request " << descriptor->request_->cookie()
>>   			<< " with " << descriptor->buffers_.size() << " streams";
>>
>> +	/*
>> +	 * Collect the CameraStream associated to each requested capture stream.
>> +	 * Since requestedStreams is an std:set<>, no duplications can happen.
>                                          std::set<>
>
>> +	 */
>> +	std::set<CameraStream *> requestedStreams;
>> +	for (const auto &[i, buffer] : utils::enumerate(descriptor->buffers_)) {
>> +		CameraStream *cameraStream = buffer.stream;
>> +
>> +		switch (cameraStream->type()) {
>> +		case CameraStream::Type::Mapped:
>> +			requestedStreams.insert(cameraStream->sourceStream());


Can sourceStream field for Mapped streams be nullptr here? Should we 
ensure it via an ASSERT?

>> +			break;
>> +
>> +		case CameraStream::Type::Direct:
>> +		case CameraStream::Type::Internal:
>> +			requestedStreams.insert(cameraStream);
>> +			break;
>> +		}
>> +	}
>> +
>> +	/*
>> +	 * Process all the Direct and Internal streams, for which the CameraStream
>> +	 * they refer to is the one that points to the right libcamera::Stream.
>> +	 *
>> +	 * Streams of type Mapped will be handled later.
>> +	 */
>>   	for (const auto &[i, buffer] : utils::enumerate(descriptor->buffers_)) {
>>   		CameraStream *cameraStream = buffer.stream;
>>   		camera3_stream_t *camera3Stream = cameraStream->camera3Stream();
>> @@ -945,14 +972,6 @@ int CameraDevice::processCaptureRequest(camera3_capture_request_t *camera3Reques
>>
>>   		switch (cameraStream->type()) {
>>   		case CameraStream::Type::Mapped:
>> -			/*
>> -			 * Mapped streams don't need buffers added to the
>> -			 * Request.
>> -			 */
>> -			LOG(HAL, Debug) << ss.str() << " (mapped)";
>> -
>> -			descriptor->pendingStreamsToProcess_.insert(
>> -				{ cameraStream, &buffer });
>>   			continue;
>>
>>   		case CameraStream::Type::Direct:
>> @@ -996,6 +1015,51 @@ int CameraDevice::processCaptureRequest(camera3_capture_request_t *camera3Reques
>>   		auto fence = std::make_unique<Fence>(std::move(acquireFence));
>>   		descriptor->request_->addBuffer(cameraStream->stream(),
>>   						frameBuffer, std::move(fence));
>> +
>> +		requestedStreams.erase(cameraStream);
>> +	}
>> +
>> +	/*
>> +	 * Now handle the Mapped streams. If no buffer has been added for them
>> +	 * as their corresponding direct source stream has not been requested,
>> +	 * add it here.


I am wondering a situation where a direct stream D, and a mapped stream 
M, is requested and M is mapped onto D so,

         M->sourceStream = D;

Provided the requestedStreams is a std::set<> where no duplications can 
happen, and given the above scenario:
I see the requestedStreams will consist of  { D } while populating the 
set in the switch-case above, which then  gets
erased from the requestedStreams (above the comment block) so now, the 
requestedStreams become an empty set { } here . . .

>> +	 */
>> +	for (const auto &[i, buffer] : utils::enumerate(descriptor->buffers_)) {
>> +		CameraStream *cameraStream = buffer.stream;
>> +		camera3_stream_t *camera3Stream = cameraStream->camera3Stream();
>> +
>> +		if (cameraStream->type() != CameraStream::Type::Mapped)
>> +			continue;
>> +
>> +		LOG(HAL, Debug) << i << " - (" << camera3Stream->width << "x"
>> +				<< camera3Stream->height << ")"
>> +				<< "[" << utils::hex(camera3Stream->format) << "] -> "
>> +				<< "(" << cameraStream->configuration().size.toString() << ")["
>> +				<< cameraStream->configuration().pixelFormat.toString() << "]"
>> +				<< " (mapped)";
>> +
>> +		MutexLocker lock(descriptor->streamsProcessMutex_);
>> +		descriptor->pendingStreamsToProcess_.insert({ cameraStream, &buffer });
>> +
>> +		/*
>> +		 * Make sure the CameraStream this stream is mapped on has been
>> +		 * added to the request.
>> +		 */
>> +		CameraStream *sourceStream = cameraStream->sourceStream();
>> +		if (requestedStreams.find(sourceStream) == requestedStreams.end())


and then while handling mapped streams, it will try to find { D }  in 
requestedStreams (which is now empty)

>> +			continue;
>> +
>> +		/*
>> +		 * If that's not the case, we need to add a buffer to the request
>> +		 * for this stream.
>> +		 */
>> +		FrameBuffer *frameBuffer = cameraStream->getBuffer();
>> +		buffer.internalBuffer = frameBuffer;
>> +
>> +		descriptor->request_->addBuffer(sourceStream->stream(),
>> +						frameBuffer, nullptr);


... and add a internal buffer for D

so we have 2 buffers for D in the end ?

>> +
>> +		requestedStreams.erase(sourceStream);
>>   	}
> We could possibily make sure here that now requestedStreams is empty,
> but that's just an additional safety check.
>
> The patch still looks ok to me.
>
>>   	/*
>> --
>> 2.30.2
>>