libcamera: v4l2_device: Simplify exportBuffers()

exportBuffers() can only operate on an existing BufferPool allocation. The
pool identifies its size through its .count() method.

Passing a count in to the exportBuffers() call is redundant and can be
incorrect if the value is not the same as the BufferPool size.

Simplify the function and remove the unnecessary argument, correcting all uses
throughout the code base.

While we're here, remove the createBuffers() helper from the V4L2DeviceTest
which only served to obfuscate which pool the buffers were being allocated for.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

src/libcamera/include/v4l2_device.h

@@ -99,7 +99,7 @@ public:
 	int getFormat(V4L2DeviceFormat *format);
 	int setFormat(V4L2DeviceFormat *format);
 
-	int exportBuffers(unsigned int count, BufferPool *pool);
+	int exportBuffers(BufferPool *pool);
 	int releaseBuffers();
 
 	int queueBuffer(Buffer *buffer);

src/libcamera/pipeline/ipu3/ipu3.cpp

@@ -191,8 +191,7 @@ int PipelineHandlerIPU3::allocateBuffers(Camera *camera, Stream *stream)
 	if (!cfg.bufferCount)
 		return -EINVAL;
 
-	int ret = data->cio2_->exportBuffers(cfg.bufferCount,
-					     &stream->bufferPool());
+	int ret = data->cio2_->exportBuffers(&stream->bufferPool());
 	if (ret) {
 		LOG(IPU3, Error) << "Failed to request memory";
 		return ret;

src/libcamera/pipeline/uvcvideo.cpp

@@ -102,7 +102,7 @@ int PipelineHandlerUVC::allocateBuffers(Camera *camera, Stream *stream)
 
 	LOG(UVC, Debug) << "Requesting " << cfg.bufferCount << " buffers";
 
-	return video_->exportBuffers(cfg.bufferCount, &stream->bufferPool());
+	return video_->exportBuffers(&stream->bufferPool());
 }
 
 int PipelineHandlerUVC::freeBuffers(Camera *camera, Stream *stream)

src/libcamera/pipeline/vimc.cpp

@@ -101,7 +101,7 @@ int PipelineHandlerVimc::allocateBuffers(Camera *camera, Stream *stream)
 
 	LOG(VIMC, Debug) << "Requesting " << cfg.bufferCount << " buffers";
 
-	return video_->exportBuffers(cfg.bufferCount, &stream->bufferPool());
+	return video_->exportBuffers(&stream->bufferPool());
 }
 
 int PipelineHandlerVimc::freeBuffers(Camera *camera, Stream *stream)

src/libcamera/v4l2_device.cpp

@@ -538,13 +538,12 @@ int V4L2Device::requestBuffers(unsigned int count)
 }
 
 /**
- * \brief Request \a count buffers to be allocated from the device and stored in
- * the buffer pool provided.
- * \param[in] count Number of buffers to allocate
+ * \brief Request buffers to be allocated from the device and stored in the
+ *  buffer pool provided.
  * \param[out] pool BufferPool to populate with buffers
  * \return 0 on success or a negative error code otherwise
  */
-int V4L2Device::exportBuffers(unsigned int count, BufferPool *pool)
+int V4L2Device::exportBuffers(BufferPool *pool)
 {
 	unsigned int allocatedBuffers;
 	unsigned int i;
@@ -552,21 +551,19 @@ int V4L2Device::exportBuffers(unsigned int count, BufferPool *pool)
 
 	memoryType_ = V4L2_MEMORY_MMAP;
 
-	ret = requestBuffers(count);
+	ret = requestBuffers(pool->count());
 	if (ret < 0)
 		return ret;
 
 	allocatedBuffers = ret;
-	if (allocatedBuffers < count) {
+	if (allocatedBuffers < pool->count()) {
 		LOG(V4L2, Error) << "Not enough buffers provided by V4L2Device";
 		requestBuffers(0);
 		return -ENOMEM;
 	}
 
-	count = ret;
-
 	/* Map the buffers. */
-	for (i = 0; i < count; ++i) {
+	for (i = 0; i < pool->count(); ++i) {
 		struct v4l2_plane planes[VIDEO_MAX_PLANES] = {};
 		struct v4l2_buffer buf = {};
 		struct Buffer &buffer = pool->buffers()[i];

test/v4l2_device/capture_async.cpp

@@ -38,9 +38,9 @@ protected:
 		Timer timeout;
 		int ret;
 
-		createBuffers(bufferCount);
+		pool_.createBuffers(bufferCount);
 
-		ret = dev_->exportBuffers(bufferCount, &pool_);
+		ret = dev_->exportBuffers(&pool_);
 		if (ret)
 			return TestFail;
 

test/v4l2_device/request_buffers.cpp

@@ -19,9 +19,9 @@ protected:
 		 */
 		const unsigned int bufferCount = 8;
 
-		createBuffers(bufferCount);
+		pool_.createBuffers(bufferCount);
 
-		int ret = dev_->exportBuffers(bufferCount, &pool_);
+		int ret = dev_->exportBuffers(&pool_);
 		if (ret)
 			return TestFail;
 

test/v4l2_device/stream_on_off.cpp

@@ -14,9 +14,9 @@ protected:
 	{
 		const unsigned int bufferCount = 8;
 
-		createBuffers(bufferCount);
+		pool_.createBuffers(bufferCount);
 
-		int ret = dev_->exportBuffers(bufferCount, &pool_);
+		int ret = dev_->exportBuffers(&pool_);
 		if (ret)
 			return TestFail;
 

test/v4l2_device/v4l2_device_test.h

@@ -24,8 +24,6 @@ class V4L2DeviceTest : public Test
 public:
 	V4L2DeviceTest() : dev_(nullptr){};
 
-	void createBuffers(unsigned int qty) { pool_.createBuffers(qty); }
-
 protected:
 	int init();
 	void cleanup();