cam: Cache buffer memory mapping

With the buffer allocator in use it's possible to cache the dmabuf
memory mappings when starting the camera instead of mapping and
unmapping them each time.

Signed-off-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

src/cam/buffer_writer.cpp

@@ -22,6 +22,27 @@ BufferWriter::BufferWriter(const std::string &pattern)
 {
 }
 
+BufferWriter::~BufferWriter()
+{
+	for (auto &iter : mappedBuffers_) {
+		void *memory = iter.second.first;
+		unsigned int length = iter.second.second;
+		munmap(memory, length);
+	}
+	mappedBuffers_.clear();
+}
+
+void BufferWriter::mapBuffer(FrameBuffer *buffer)
+{
+	for (const FrameBuffer::Plane &plane : buffer->planes()) {
+		void *memory = mmap(NULL, plane.length, PROT_READ, MAP_SHARED,
+				    plane.fd.fd(), 0);
+
+		mappedBuffers_[plane.fd.fd()] =
+			std::make_pair(memory, plane.length);
+	}
+}
+
 int BufferWriter::write(FrameBuffer *buffer, const std::string &streamName)
 {
 	std::string filename;
@@ -44,9 +65,7 @@ int BufferWriter::write(FrameBuffer *buffer, const std::string &streamName)
 		return -errno;
 
 	for (const FrameBuffer::Plane &plane : buffer->planes()) {
-		/* \todo Once the FrameBuffer is done cache mapped memory. */
-		void *data = mmap(NULL, plane.length, PROT_READ, MAP_SHARED,
-				  plane.fd.fd(), 0);
+		void *data = mappedBuffers_[plane.fd.fd()].first;
 		unsigned int length = plane.length;
 
 		ret = ::write(fd, data, length);
@@ -61,8 +80,6 @@ int BufferWriter::write(FrameBuffer *buffer, const std::string &streamName)
 				  << length << std::endl;
 			break;
 		}
-
-		munmap(data, length);
 	}
 
 	close(fd);