3 files changed, 63 insertions, 2 deletions

diff --git a/src/libcamera/buffer.cpp b/src/libcamera/buffer.cpp
index ecbf2524..99358633 100644
--- a/src/libcamera/buffer.cpp
+++ b/src/libcamera/buffer.cpp
@@ -269,7 +269,8 @@ void BufferPool::destroyBuffers()
  * for a stream with Stream::createBuffer().
  */
 Buffer::Buffer(unsigned int index, const Buffer *metadata)
-	: index_(index), status_(Buffer::BufferSuccess), request_(nullptr),
+	: index_(index), dmabuf_({ -1, -1, -1 }),
+	  status_(Buffer::BufferSuccess), request_(nullptr),
 	  stream_(nullptr)
 {
 	if (metadata) {
@@ -290,6 +291,16 @@ Buffer::Buffer(unsigned int index, const Buffer *metadata)
  */
 
 /**
+ * \fn Buffer::dmabufs()
+ * \brief Retrieve the dmabuf file descriptors for all buffer planes
+ *
+ * The dmabufs array contains one dmabuf file descriptor per plane. Unused
+ * entries are set to -1.
+ *
+ * \return The dmabuf file descriptors
+ */
+
+/**
  * \fn Buffer::bytesused()
  * \brief Retrieve the number of bytes occupied by the data in the buffer
  * \return Number of bytes occupied in the buffer
diff --git a/src/libcamera/request.cpp b/src/libcamera/request.cpp
index 19131472..ee2158fc 100644
--- a/src/libcamera/request.cpp
+++ b/src/libcamera/request.cpp
@@ -106,10 +106,15 @@ Request::~Request()
  *
  * \return 0 on success or a negative error code otherwise
  * \retval -EEXIST The request already contains a buffer for the stream
+ * \retval -EINVAL The buffer does not reference a valid Stream
  */
 int Request::addBuffer(std::unique_ptr<Buffer> buffer)
 {
 	Stream *stream = buffer->stream();
+	if (!stream) {
+		LOG(Request, Error) << "Invalid stream reference";
+		return -EINVAL;
+	}
 
 	auto it = bufferMap_.find(stream);
 	if (it != bufferMap_.end()) {
diff --git a/src/libcamera/stream.cpp b/src/libcamera/stream.cpp
index 37a9bc0a..98178e06 100644
--- a/src/libcamera/stream.cpp
+++ b/src/libcamera/stream.cpp
@@ -424,17 +424,26 @@ Stream::Stream()
 }
 
 /**
- * \brief Create a Buffer instance
+ * \brief Create a Buffer instance referencing the memory buffer \a index
  * \param[in] index The desired buffer index
  *
  * This method creates a Buffer instance that references a BufferMemory from
  * the stream's buffers pool by its \a index. The index shall be lower than the
  * number of buffers in the pool.
  *
+ * This method is only valid for streams that use the InternalMemory type. It
+ * will return a null pointer when called on streams using the ExternalMemory
+ * type.
+ *
  * \return A newly created Buffer on success or nullptr otherwise
  */
 std::unique_ptr<Buffer> Stream::createBuffer(unsigned int index)
 {
+	if (memoryType_ != InternalMemory) {
+		LOG(Stream, Error) << "Invalid stream memory type";
+		return nullptr;
+	}
+
 	if (index >= bufferPool_.count()) {
 		LOG(Stream, Error) << "Invalid buffer index " << index;
 		return nullptr;
@@ -448,6 +457,42 @@ std::unique_ptr<Buffer> Stream::createBuffer(unsigned int index)
 }
 
 /**
+ * \brief Create a Buffer instance that represents a memory area identified by
+ * dmabuf file descriptors
+ * \param[in] fds The dmabuf file descriptors for each plane
+ *
+ * This method creates a Buffer instance that references buffer memory
+ * allocated outside of libcamera through dmabuf file descriptors. The \a
+ * dmabuf array shall contain a file descriptor for each plane in the buffer,
+ * and unused entries shall be set to -1.
+ *
+ * The buffer is created without a valid index, as it does not yet map to any of
+ * the stream's BufferMemory instances. An index will be assigned at the time
+ * the buffer is queued to the camera in a request. Applications may thus
+ * create any number of Buffer instances, providing that no more than the
+ * number of buffers allocated for the stream are queued at any given time.
+ *
+ * This method is only valid for streams that use the ExternalMemory type. It
+ * will return a null pointer when called on streams using the InternalMemory
+ * type.
+ *
+ * \return A newly created Buffer on success or nullptr otherwise
+ */
+std::unique_ptr<Buffer> Stream::createBuffer(const std::array<int, 3> &fds)
+{
+	if (memoryType_ != ExternalMemory) {
+		LOG(Stream, Error) << "Invalid stream memory type";
+		return nullptr;
+	}
+
+	Buffer *buffer = new Buffer();
+	buffer->dmabuf_ = fds;
+	buffer->stream_ = this;
+
+	return std::unique_ptr<Buffer>(buffer);
+}
+
+/**
  * \fn Stream::bufferPool()
  * \brief Retrieve the buffer pool for the stream
  *