[libcamera-devel] [PATCH v3 30/30] v4l2: Sum bytesused for all planes when dequeuing buffer

[Jean-Michel Hautbois]

Hi Laurent,

On 07/09/2021 16:17, Kieran Bingham wrote:
> On 06/09/2021 23:56, Laurent Pinchart wrote:
>> The V4L2 compatibility layer supports the single-planar API only, and
>> thuss expose a single V4L2 buffer plane to applications, regardless of
> 
> s/thuss/thus/
> s/expose/exposes/
> 
>> the number of planes in the FrameBuffer. For multi-planar frame buffers,
>> the bytesused value isn't correct as it only takes the first plane into
>> account. Fix it by summing the bytesused values for all FrameBuffer
>> planes.
>>
>> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
>> ---
>>  src/v4l2/v4l2_camera_proxy.cpp | 7 ++++++-
>>  1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/src/v4l2/v4l2_camera_proxy.cpp b/src/v4l2/v4l2_camera_proxy.cpp
>> index 07d2250bb846..aeffef26c5bf 100644
>> --- a/src/v4l2/v4l2_camera_proxy.cpp
>> +++ b/src/v4l2/v4l2_camera_proxy.cpp
>> @@ -11,6 +11,7 @@
>>  #include <array>
>>  #include <errno.h>
>>  #include <linux/videodev2.h>
>> +#include <numeric>
>>  #include <set>
>>  #include <string.h>
>>  #include <sys/mman.h>
>> @@ -211,7 +212,11 @@ void V4L2CameraProxy::updateBuffers()
>>  
>>  		switch (fmd.status) {
>>  		case FrameMetadata::FrameSuccess:
>> -			buf.bytesused = fmd.planes()[0].bytesused;
>> +			buf.bytesused = std::accumulate(fmd.planes().begin(),
>> +							fmd.planes().end(), 0,
>> +							[](unsigned int total, const auto &plane) {
> 
> lambda's always look like black magic to me.
> I assume total is either automatically initialised, or initialised by
> the 0 after fmd.planes().end()

I read back cpp reference for that one :-), and yes, total takes the
value of init, which is 0.

> 
> Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
Reviewed-by: Jean-Michel Hautbois <jeanmichel.hautbois at ideasonboard.com>
> 
>> +								return total + plane.bytesused;
>> +							});
>>  			buf.field = V4L2_FIELD_NONE;
>>  			buf.timestamp.tv_sec = fmd.timestamp / 1000000000;
>>  			buf.timestamp.tv_usec = fmd.timestamp % 1000000;
>>