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>

5 files changed, 10 insertions, 14 deletions

diff --git a/src/libcamera/include/v4l2_device.h b/src/libcamera/include/v4l2_device.h
index 983b9d90..5a536393 100644
--- a/src/libcamera/include/v4l2_device.h
+++ b/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);
diff --git a/src/libcamera/pipeline/ipu3/ipu3.cpp b/src/libcamera/pipeline/ipu3/ipu3.cpp
index 34b03995..677e127d 100644
--- a/src/libcamera/pipeline/ipu3/ipu3.cpp
+++ b/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;
diff --git a/src/libcamera/pipeline/uvcvideo.cpp b/src/libcamera/pipeline/uvcvideo.cpp
index fc31c52c..b6a98657 100644
--- a/src/libcamera/pipeline/uvcvideo.cpp
+++ b/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)
diff --git a/src/libcamera/pipeline/vimc.cpp b/src/libcamera/pipeline/vimc.cpp
index 46840a4f..543ff212 100644
--- a/src/libcamera/pipeline/vimc.cpp
+++ b/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)
diff --git a/src/libcamera/v4l2_device.cpp b/src/libcamera/v4l2_device.cpp
index 207ba933..ca6bb4ee 100644
--- a/src/libcamera/v4l2_device.cpp
+++ b/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];