[libcamera-devel] [RFC PATCH 7/8] android: camera_device: Query plane length

[Kieran Bingham]

Use lseek to query the length of planes where possible rather than leaving
the plane.length as zero, which prevents mapping buffers for software
processing.

Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
---

I like this one ;-) We need to know the plane lengths for software
streams now, but the correct way to get this would be to talk to the
gralloc allocator. This would mean pulling in various extra
cros-specific libraries, where instead we can query the size of the
dmabuf by getting the offset when we SEEK_END.


 src/android/camera_device.cpp | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/src/android/camera_device.cpp b/src/android/camera_device.cpp
index 538b8ab5da03..6212ccdd61ec 100644
--- a/src/android/camera_device.cpp
+++ b/src/android/camera_device.cpp
@@ -1045,12 +1045,18 @@ FrameBuffer *CameraDevice::createFrameBuffer(const buffer_handle_t camera3buffer
 			continue;
 		}
 
-		/*
-		 * Setting length to zero here is OK as the length is only used
-		 * to map the memory of the plane. Libcamera do not need to poke
-		 * at the memory content queued by the HAL.
-		 */
-		plane.length = 0;
+		off_t length = lseek(plane.fd.fd(), 0, SEEK_END);
+		if (length == -1) {
+			/*
+			 * A zero length plane is not fatal unless the
+			 * FrameBuffer is used for a software stream, libcamera
+			 * itself will not access the internal frame content.
+			 */
+			LOG(HAL, Error) << "Failed to query plane length";
+			length = 0;
+		}
+
+		plane.length = length;
 		planes.push_back(std::move(plane));
 	}
 
-- 
2.25.1