[libcamera-devel] [PATCH 1/2] android: wait on fences in CameraStream::process()

[Jacopo Mondi]

Acquisition fences for streams generated by post-processing are not
correctly handled and are currently ignored by the camera HAL.

Add a waitFence() function to the CameraStream class to be executed before
starting the post-processing in CameraStream::process().

The CameraStream::waitFence() implementation is copied from the
CameraWorker::Worker::waitFence() one, and both should be replaced by a
libcamera core mechanism.

Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
---
 src/android/camera_device.cpp |  2 +-
 src/android/camera_stream.cpp | 47 ++++++++++++++++++++++++++++++++++-
 src/android/camera_stream.h   |  4 ++-
 3 files changed, 50 insertions(+), 3 deletions(-)

diff --git a/src/android/camera_device.cpp b/src/android/camera_device.cpp
index 21844e5114a9..db35947afc2f 100644
--- a/src/android/camera_device.cpp
+++ b/src/android/camera_device.cpp
@@ -1179,7 +1179,7 @@ void CameraDevice::requestComplete(Request *request)
 			continue;
 		}
 
-		int ret = cameraStream->process(*src, *buffer.buffer,
+		int ret = cameraStream->process(*src, buffer,
 						descriptor.settings_,
 						resultMetadata.get());
 		/*
diff --git a/src/android/camera_stream.cpp b/src/android/camera_stream.cpp
index e30c7ee4fcb3..c723da2c6407 100644
--- a/src/android/camera_stream.cpp
+++ b/src/android/camera_stream.cpp
@@ -7,7 +7,10 @@
 
 #include "camera_stream.h"
 
+#include <errno.h>
 #include <sys/mman.h>
+#include <sys/poll.h>
+#include <unistd.h>
 
 #include <libcamera/formats.h>
 
@@ -109,11 +112,52 @@ int CameraStream::configure()
 	return 0;
 }
 
+int CameraStream::waitFence(int fence)
+{
+	/*
+	 * \todo The implementation here is copied from camera_worker.cpp
+	 * and both should be removed once libcamera is instrumented to handle
+	 * fences waiting in the core.
+	 *
+	 * \todo Better characterize the timeout. Currently equal to the one
+	 * used by the Rockchip Camera HAL on ChromeOS.
+	 */
+	constexpr unsigned int timeoutMs = 300;
+	struct pollfd fds = { fence, POLLIN, 0 };
+
+	do {
+		int ret = poll(&fds, 1, timeoutMs);
+		if (ret == 0)
+			return -ETIME;
+
+		if (ret > 0) {
+			if (fds.revents & (POLLERR | POLLNVAL))
+				return -EINVAL;
+
+			return 0;
+		}
+	} while (errno == EINTR || errno == EAGAIN);
+
+	return -errno;
+}
+
 int CameraStream::process(const FrameBuffer &source,
-			  buffer_handle_t camera3Dest,
+			  camera3_stream_buffer_t &camera3Buffer,
 			  const CameraMetadata &requestMetadata,
 			  CameraMetadata *resultMetadata)
 {
+	/* Handle waiting on fences on the destination buffer. */
+	int fence = camera3Buffer.acquire_fence;
+	if (fence != -1) {
+		int ret = waitFence(fence);
+		::close(fence);
+		if (ret < 0) {
+			LOG(HAL, Error) << "Failed waiting for fence: "
+					<< fence << ": " << strerror(-ret);
+			return ret;
+		}
+	}
+
 	if (!postProcessor_)
 		return 0;
 
@@ -122,6 +166,7 @@ int CameraStream::process(const FrameBuffer &source,
 	 * separate thread.
 	 */
 	const StreamConfiguration &output = configuration();
+	buffer_handle_t &camera3Dest = *camera3Buffer.buffer;
 	CameraBuffer dest(camera3Dest, formats::MJPEG, output.size,
 			  PROT_READ | PROT_WRITE);
 	if (!dest.isValid()) {
diff --git a/src/android/camera_stream.h b/src/android/camera_stream.h
index 2dab6c3a37d1..1566e5e4009c 100644
--- a/src/android/camera_stream.h
+++ b/src/android/camera_stream.h
@@ -119,7 +119,7 @@ public:
 
 	int configure();
 	int process(const libcamera::FrameBuffer &source,
-		    buffer_handle_t camera3Dest,
+		    camera3_stream_buffer_t &camera3Buffer,
 		    const CameraMetadata &requestMetadata,
 		    CameraMetadata *resultMetadata);
 	libcamera::FrameBuffer *getBuffer();
@@ -132,6 +132,8 @@ private:
 	camera3_stream_t *camera3Stream_;
 	const unsigned int index_;
 
+	int waitFence(int fence);
+
 	std::unique_ptr<libcamera::FrameBufferAllocator> allocator_;
 	std::vector<libcamera::FrameBuffer *> buffers_;
 	/*
-- 
2.32.0