[media] videobuf2-core.h: move function descriptions from c file

There are several functions that were documented at the .c
file. As we only include the headers, we need to move them to
there, in order to have documentation.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

2 files changed, 269 insertions, 254 deletions

diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
index bfe85879c563..21900202ff83 100644
--- a/drivers/media/v4l2-core/videobuf2-core.c
+++ b/drivers/media/v4l2-core/videobuf2-core.c
@@ -528,10 +528,6 @@ static int __vb2_queue_free(struct vb2_queue *q, unsigned int buffers)
         return 0;
 }
 
-/**
- * vb2_buffer_in_use() - return true if the buffer is in use and
- * the queue cannot be freed (by the means of REQBUFS(0)) call
- */
 bool vb2_buffer_in_use(struct vb2_queue *q, struct vb2_buffer *vb)
 {
         unsigned int plane;
@@ -564,16 +560,6 @@ static bool __buffers_in_use(struct vb2_queue *q)
         return false;
 }
 
-/**
- * vb2_core_querybuf() - query video buffer information
- * @q:          videobuf queue
- * @index:      id number of the buffer
- * @pb:         buffer struct passed from userspace
- *
- * Should be called from vidioc_querybuf ioctl handler in driver.
- * The passed buffer should have been verified.
- * This function fills the relevant information for the userspace.
- */
 void vb2_core_querybuf(struct vb2_queue *q, unsigned int index, void *pb)
 {
         call_void_bufop(q, fill_user_buffer, q->bufs[index], pb);
@@ -620,10 +606,6 @@ static int __verify_dmabuf_ops(struct vb2_queue *q)
         return 0;
 }
 
-/**
- * vb2_verify_memory_type() - Check whether the memory type and buffer type
- * passed to a buffer operation are compatible with the queue.
- */
 int vb2_verify_memory_type(struct vb2_queue *q,
                 enum vb2_memory memory, unsigned int type)
 {
@@ -670,30 +652,6 @@ int vb2_verify_memory_type(struct vb2_queue *q,
 }
 EXPORT_SYMBOL(vb2_verify_memory_type);
 
-/**
- * vb2_core_reqbufs() - Initiate streaming
- * @q:          videobuf2 queue
- * @memory: memory type
- * @count: requested buffer count
- *
- * Should be called from vidioc_reqbufs ioctl handler of a driver.
- * This function:
- * 1) verifies streaming parameters passed from the userspace,
- * 2) sets up the queue,
- * 3) negotiates number of buffers and planes per buffer with the driver
- *    to be used during streaming,
- * 4) allocates internal buffer structures (struct vb2_buffer), according to
- *    the agreed parameters,
- * 5) for MMAP memory type, allocates actual video memory, using the
- *    memory handling/allocation routines provided during queue initialization
- *
- * If req->count is 0, all the memory will be freed instead.
- * If the queue has been allocated previously (by a previous vb2_reqbufs) call
- * and the queue is not busy, memory will be reallocated.
- *
- * The return values from this function are intended to be directly returned
- * from vidioc_reqbufs handler in driver.
- */
 int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
                 unsigned int *count)
 {
@@ -819,22 +777,6 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
 }
 EXPORT_SYMBOL_GPL(vb2_core_reqbufs);
 
-/**
- * vb2_core_create_bufs() - Allocate buffers and any required auxiliary structs
- * @q:          videobuf2 queue
- * @memory: memory type
- * @count: requested buffer count
- * @parg: parameter passed to device driver
- *
- * Should be called from vidioc_create_bufs ioctl handler of a driver.
- * This function:
- * 1) verifies parameter sanity
- * 2) calls the .queue_setup() queue operation
- * 3) performs any necessary memory allocations
- *
- * The return values from this function are intended to be directly returned
- * from vidioc_create_bufs handler in driver.
- */
 int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
                 unsigned int *count, unsigned requested_planes,
                 const unsigned requested_sizes[])
@@ -924,14 +866,6 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
 }
 EXPORT_SYMBOL_GPL(vb2_core_create_bufs);
 
-/**
- * vb2_plane_vaddr() - Return a kernel virtual address of a given plane
- * @vb:         vb2_buffer to which the plane in question belongs to
- * @plane_no:   plane number for which the address is to be returned
- *
- * This function returns a kernel virtual address of a given plane if
- * such a mapping exist, NULL otherwise.
- */
 void *vb2_plane_vaddr(struct vb2_buffer *vb, unsigned int plane_no)
 {
         if (plane_no > vb->num_planes || !vb->planes[plane_no].mem_priv)
@@ -942,17 +876,6 @@ void *vb2_plane_vaddr(struct vb2_buffer *vb, unsigned int plane_no)
 }
 EXPORT_SYMBOL_GPL(vb2_plane_vaddr);
 
-/**
- * vb2_plane_cookie() - Return allocator specific cookie for the given plane
- * @vb:         vb2_buffer to which the plane in question belongs to
- * @plane_no:   plane number for which the cookie is to be returned
- *
- * This function returns an allocator specific cookie for a given plane if
- * available, NULL otherwise. The allocator should provide some simple static
- * inline function, which would convert this cookie to the allocator specific
- * type that can be used directly by the driver to access the buffer. This can
- * be for example physical address, pointer to scatter list or IOMMU mapping.
- */
 void *vb2_plane_cookie(struct vb2_buffer *vb, unsigned int plane_no)
 {
         if (plane_no >= vb->num_planes || !vb->planes[plane_no].mem_priv)
@@ -962,26 +885,6 @@ void *vb2_plane_cookie(struct vb2_buffer *vb, unsigned int plane_no)
 }
 EXPORT_SYMBOL_GPL(vb2_plane_cookie);
 
-/**
- * vb2_buffer_done() - inform videobuf that an operation on a buffer is finished
- * @vb:         vb2_buffer returned from the driver
- * @state:      either VB2_BUF_STATE_DONE if the operation finished successfully,
- *              VB2_BUF_STATE_ERROR if the operation finished with an error or
- *              VB2_BUF_STATE_QUEUED if the driver wants to requeue buffers.
- *              If start_streaming fails then it should return buffers with state
- *              VB2_BUF_STATE_QUEUED to put them back into the queue.
- *
- * This function should be called by the driver after a hardware operation on
- * a buffer is finished and the buffer may be returned to userspace. The driver
- * cannot use this buffer anymore until it is queued back to it by videobuf
- * by the means of buf_queue callback. Only buffers previously queued to the
- * driver by buf_queue can be passed to this function.
- *
- * While streaming a buffer can only be returned in state DONE or ERROR.
- * The start_streaming op can also return them in case the DMA engine cannot
- * be started for some reason. In that case the buffers should be returned with
- * state QUEUED.
- */
 void vb2_buffer_done(struct vb2_buffer *vb, enum vb2_buffer_state state)
 {
         struct vb2_queue *q = vb->vb2_queue;
@@ -1040,18 +943,6 @@ void vb2_buffer_done(struct vb2_buffer *vb, enum vb2_buffer_state state)
 }
 EXPORT_SYMBOL_GPL(vb2_buffer_done);
 
-/**
- * vb2_discard_done() - discard all buffers marked as DONE
- * @q:          videobuf2 queue
- *
- * This function is intended to be used with suspend/resume operations. It
- * discards all 'done' buffers as they would be too old to be requested after
- * resume.
- *
- * Drivers must stop the hardware and synchronize with interrupt handlers and/or
- * delayed works before calling this function to make sure no buffer will be
- * touched by the driver and/or hardware.
- */
 void vb2_discard_done(struct vb2_queue *q)
 {
         struct vb2_buffer *vb;
@@ -1384,22 +1275,6 @@ static int __buf_prepare(struct vb2_buffer *vb, const void *pb)
         return ret;
 }
 
-/**
- * vb2_core_prepare_buf() - Pass ownership of a buffer from userspace
- *                      to the kernel
- * @q:          videobuf2 queue
- * @index:      id number of the buffer
- * @pb:         buffer structure passed from userspace to vidioc_prepare_buf
- *              handler in driver
- *
- * Should be called from vidioc_prepare_buf ioctl handler of a driver.
- * The passed buffer should have been verified.
- * This function calls buf_prepare callback in the driver (if provided),
- * in which driver-specific buffer initialization can be performed,
- *
- * The return values from this function are intended to be directly returned
- * from vidioc_prepare_buf handler in driver.
- */
 int vb2_core_prepare_buf(struct vb2_queue *q, unsigned int index, void *pb)
 {
         struct vb2_buffer *vb;
@@ -1488,24 +1363,6 @@ static int vb2_start_streaming(struct vb2_queue *q)
         return ret;
 }
 
-/**
- * vb2_core_qbuf() - Queue a buffer from userspace
- * @q:          videobuf2 queue
- * @index:      id number of the buffer
- * @pb:         buffer structure passed from userspace to vidioc_qbuf handler
- *              in driver
- *
- * Should be called from vidioc_qbuf ioctl handler of a driver.
- * The passed buffer should have been verified.
- * This function:
- * 1) if necessary, calls buf_prepare callback in the driver (if provided), in
- *    which driver-specific buffer initialization can be performed,
- * 2) if streaming is on, queues the buffer in driver by the means of buf_queue
- *    callback for processing.
- *
- * The return values from this function are intended to be directly returned
- * from vidioc_qbuf handler in driver.
- */
 int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb)
 {
         struct vb2_buffer *vb;
@@ -1686,15 +1543,6 @@ static int __vb2_get_done_vb(struct vb2_queue *q, struct vb2_buffer **vb,
         return ret;
 }
 
-/**
- * vb2_wait_for_all_buffers() - wait until all buffers are given back to vb2
- * @q:          videobuf2 queue
- *
- * This function will wait until all buffers that have been given to the driver
- * by buf_queue() are given back to vb2 with vb2_buffer_done(). It doesn't call
- * wait_prepare, wait_finish pair. It is intended to be called with all locks
- * taken, for example from stop_streaming() callback.
- */
 int vb2_wait_for_all_buffers(struct vb2_queue *q)
 {
         if (!q->streaming) {
@@ -1732,28 +1580,6 @@ static void __vb2_dqbuf(struct vb2_buffer *vb)
                 }
 }
 
-/**
- * vb2_core_dqbuf() - Dequeue a buffer to the userspace
- * @q:          videobuf2 queue
- * @pindex:     pointer to the buffer index. May be NULL
- * @pb:         buffer structure passed from userspace to vidioc_dqbuf handler
- *              in driver
- * @nonblocking: if true, this call will not sleep waiting for a buffer if no
- *               buffers ready for dequeuing are present. Normally the driver
- *               would be passing (file->f_flags & O_NONBLOCK) here
- *
- * Should be called from vidioc_dqbuf ioctl handler of a driver.
- * The passed buffer should have been verified.
- * This function:
- * 1) calls buf_finish callback in the driver (if provided), in which
- *    driver can perform any additional operations that may be required before
- *    returning the buffer to userspace, such as cache sync,
- * 2) the buffer struct members are filled with relevant information for
- *    the userspace.
- *
- * The return values from this function are intended to be directly returned
- * from vidioc_dqbuf handler in driver.
- */
 int vb2_core_dqbuf(struct vb2_queue *q, unsigned int *pindex, void *pb,
                    bool nonblocking)
 {
@@ -1917,19 +1743,6 @@ int vb2_core_streamon(struct vb2_queue *q, unsigned int type)
 }
 EXPORT_SYMBOL_GPL(vb2_core_streamon);
 
-/**
- * vb2_queue_error() - signal a fatal error on the queue
- * @q:          videobuf2 queue
- *
- * Flag that a fatal unrecoverable error has occurred and wake up all processes
- * waiting on the queue. Polling will now set POLLERR and queuing and dequeuing
- * buffers will return -EIO.
- *
- * The error flag will be cleared when cancelling the queue, either from
- * vb2_streamoff or vb2_queue_release. Drivers should thus not call this
- * function before starting the stream, otherwise the error flag will remain set
- * until the queue is released when closing the device node.
- */
 void vb2_queue_error(struct vb2_queue *q)
 {
         q->error = 1;
@@ -1992,19 +1805,6 @@ static int __find_plane_by_offset(struct vb2_queue *q, unsigned long off,
         return -EINVAL;
 }
 
-/**
- * vb2_core_expbuf() - Export a buffer as a file descriptor
- * @q:          videobuf2 queue
- * @fd:         file descriptor associated with DMABUF (set by driver) *
- * @type:       buffer type
- * @index:      id number of the buffer
- * @plane:      index of the plane to be exported, 0 for single plane queues
- * @flags:      flags for newly created file, currently only O_CLOEXEC is
- *              supported, refer to manual of open syscall for more details
- *
- * The return values from this function are intended to be directly returned
- * from vidioc_expbuf handler in driver.
- */
 int vb2_core_expbuf(struct vb2_queue *q, int *fd, unsigned int type,
                 unsigned int index, unsigned int plane, unsigned int flags)
 {
@@ -2076,25 +1876,6 @@ int vb2_core_expbuf(struct vb2_queue *q, int *fd, unsigned int type,
 }
 EXPORT_SYMBOL_GPL(vb2_core_expbuf);
 
-/**
- * vb2_mmap() - map video buffers into application address space
- * @q:          videobuf2 queue
- * @vma:        vma passed to the mmap file operation handler in the driver
- *
- * Should be called from mmap file operation handler of a driver.
- * This function maps one plane of one of the available video buffers to
- * userspace. To map whole video memory allocated on reqbufs, this function
- * has to be called once per each plane per each buffer previously allocated.
- *
- * When the userspace application calls mmap, it passes to it an offset returned
- * to it earlier by the means of vidioc_querybuf handler. That offset acts as
- * a "cookie", which is then used to identify the plane to be mapped.
- * This function finds a plane with a matching offset and a mapping is performed
- * by the means of a provided memory operation.
- *
- * The return values from this function are intended to be directly returned
- * from the mmap handler in driver.
- */
 int vb2_mmap(struct vb2_queue *q, struct vm_area_struct *vma)
 {
         unsigned long off = vma->vm_pgoff << PAGE_SHIFT;
@@ -2196,17 +1977,6 @@ unsigned long vb2_get_unmapped_area(struct vb2_queue *q,
 EXPORT_SYMBOL_GPL(vb2_get_unmapped_area);
 #endif
 
-/**
- * vb2_core_queue_init() - initialize a videobuf2 queue
- * @q:          videobuf2 queue; this structure should be allocated in driver
- *
- * The vb2_queue structure should be allocated by the driver. The driver is
- * responsible of clearing it's content and setting initial values for some
- * required entries before calling this function.
- * q->ops, q->mem_ops, q->type and q->io_modes are mandatory. Please refer
- * to the struct vb2_queue description in include/media/videobuf2-core.h
- * for more information.
- */
 int vb2_core_queue_init(struct vb2_queue *q)
 {
         /*
@@ -2236,14 +2006,6 @@ EXPORT_SYMBOL_GPL(vb2_core_queue_init);
 
 static int __vb2_init_fileio(struct vb2_queue *q, int read);
 static int __vb2_cleanup_fileio(struct vb2_queue *q);
-/**
- * vb2_core_queue_release() - stop streaming, release the queue and free memory
- * @q:          videobuf2 queue
- *
- * This function stops streaming and performs necessary clean ups, including
- * freeing video buffer memory. The driver is responsible for freeing
- * the vb2_queue structure itself.
- */
 void vb2_core_queue_release(struct vb2_queue *q)
 {
         __vb2_cleanup_fileio(q);
@@ -2254,22 +2016,6 @@ void vb2_core_queue_release(struct vb2_queue *q)
 }
 EXPORT_SYMBOL_GPL(vb2_core_queue_release);
 
-/**
- * vb2_core_poll() - implements poll userspace operation
- * @q:          videobuf2 queue
- * @file:       file argument passed to the poll file operation handler
- * @wait:       wait argument passed to the poll file operation handler
- *
- * This function implements poll file operation handler for a driver.
- * For CAPTURE queues, if a buffer is ready to be dequeued, the userspace will
- * be informed that the file descriptor of a video device is available for
- * reading.
- * For OUTPUT queues, if a buffer is ready to be dequeued, the file descriptor
- * will be reported as available for writing.
- *
- * The return values from this function are intended to be directly returned
- * from poll handler in driver.
- */
 unsigned int vb2_core_poll(struct vb2_queue *q, struct file *file,
                 poll_table *wait)
 {
diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index b6546db670ca..68f93dacb38f 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -536,35 +536,274 @@ struct vb2_queue {
 #endif
 };
 
+/**
+ * vb2_plane_vaddr() - Return a kernel virtual address of a given plane
+ * @vb:         vb2_buffer to which the plane in question belongs to
+ * @plane_no:   plane number for which the address is to be returned
+ *
+ * This function returns a kernel virtual address of a given plane if
+ * such a mapping exist, NULL otherwise.
+ */
 void *vb2_plane_vaddr(struct vb2_buffer *vb, unsigned int plane_no);
+
+/**
+ * vb2_plane_cookie() - Return allocator specific cookie for the given plane
+ * @vb:         vb2_buffer to which the plane in question belongs to
+ * @plane_no:   plane number for which the cookie is to be returned
+ *
+ * This function returns an allocator specific cookie for a given plane if
+ * available, NULL otherwise. The allocator should provide some simple static
+ * inline function, which would convert this cookie to the allocator specific
+ * type that can be used directly by the driver to access the buffer. This can
+ * be for example physical address, pointer to scatter list or IOMMU mapping.
+ */
 void *vb2_plane_cookie(struct vb2_buffer *vb, unsigned int plane_no);
 
+/**
+ * vb2_buffer_done() - inform videobuf that an operation on a buffer is finished
+ * @vb:         vb2_buffer returned from the driver
+ * @state:      either %VB2_BUF_STATE_DONE if the operation finished successfully,
+ *              %VB2_BUF_STATE_ERROR if the operation finished with an error or
+ *              %VB2_BUF_STATE_QUEUED if the driver wants to requeue buffers.
+ *              If start_streaming fails then it should return buffers with state
+ *              %VB2_BUF_STATE_QUEUED to put them back into the queue.
+ *
+ * This function should be called by the driver after a hardware operation on
+ * a buffer is finished and the buffer may be returned to userspace. The driver
+ * cannot use this buffer anymore until it is queued back to it by videobuf
+ * by the means of buf_queue callback. Only buffers previously queued to the
+ * driver by buf_queue can be passed to this function.
+ *
+ * While streaming a buffer can only be returned in state DONE or ERROR.
+ * The start_streaming op can also return them in case the DMA engine cannot
+ * be started for some reason. In that case the buffers should be returned with
+ * state QUEUED.
+ */
 void vb2_buffer_done(struct vb2_buffer *vb, enum vb2_buffer_state state);
+
+/**
+ * vb2_discard_done() - discard all buffers marked as DONE
+ * @q:          videobuf2 queue
+ *
+ * This function is intended to be used with suspend/resume operations. It
+ * discards all 'done' buffers as they would be too old to be requested after
+ * resume.
+ *
+ * Drivers must stop the hardware and synchronize with interrupt handlers and/or
+ * delayed works before calling this function to make sure no buffer will be
+ * touched by the driver and/or hardware.
+ */
 void vb2_discard_done(struct vb2_queue *q);
+
+/**
+ * vb2_wait_for_all_buffers() - wait until all buffers are given back to vb2
+ * @q:          videobuf2 queue
+ *
+ * This function will wait until all buffers that have been given to the driver
+ * by buf_queue() are given back to vb2 with vb2_buffer_done(). It doesn't call
+ * wait_prepare, wait_finish pair. It is intended to be called with all locks
+ * taken, for example from stop_streaming() callback.
+ */
 int vb2_wait_for_all_buffers(struct vb2_queue *q);
 
+/**
+ * vb2_core_querybuf() - query video buffer information
+ * @q:          videobuf queue
+ * @index:      id number of the buffer
+ * @pb:         buffer struct passed from userspace
+ *
+ * Should be called from vidioc_querybuf ioctl handler in driver.
+ * The passed buffer should have been verified.
+ * This function fills the relevant information for the userspace.
+ */
 void vb2_core_querybuf(struct vb2_queue *q, unsigned int index, void *pb);
+
+/**
+ * vb2_core_reqbufs() - Initiate streaming
+ * @q:          videobuf2 queue
+ * @memory: memory type
+ * @count: requested buffer count
+ *
+ * Should be called from vidioc_reqbufs ioctl handler of a driver.
+ * This function:
+ * 1) verifies streaming parameters passed from the userspace,
+ * 2) sets up the queue,
+ * 3) negotiates number of buffers and planes per buffer with the driver
+ *    to be used during streaming,
+ * 4) allocates internal buffer structures (struct vb2_buffer), according to
+ *    the agreed parameters,
+ * 5) for MMAP memory type, allocates actual video memory, using the
+ *    memory handling/allocation routines provided during queue initialization
+ *
+ * If req->count is 0, all the memory will be freed instead.
+ * If the queue has been allocated previously (by a previous vb2_reqbufs) call
+ * and the queue is not busy, memory will be reallocated.
+ *
+ * The return values from this function are intended to be directly returned
+ * from vidioc_reqbufs handler in driver.
+ */
 int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
                 unsigned int *count);
+
+/**
+ * vb2_core_create_bufs() - Allocate buffers and any required auxiliary structs
+ * @q:          videobuf2 queue
+ * @memory: memory type
+ * @count: requested buffer count
+ * @parg: parameter passed to device driver
+ *
+ * Should be called from vidioc_create_bufs ioctl handler of a driver.
+ * This function:
+ * 1) verifies parameter sanity
+ * 2) calls the .queue_setup() queue operation
+ * 3) performs any necessary memory allocations
+ *
+ * The return values from this function are intended to be directly returned
+ * from vidioc_create_bufs handler in driver.
+ */
 int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
                 unsigned int *count, unsigned requested_planes,
                 const unsigned int requested_sizes[]);
+
+/**
+ * vb2_core_prepare_buf() - Pass ownership of a buffer from userspace
+ *                      to the kernel
+ * @q:          videobuf2 queue
+ * @index:      id number of the buffer
+ * @pb:         buffer structure passed from userspace to vidioc_prepare_buf
+ *              handler in driver
+ *
+ * Should be called from vidioc_prepare_buf ioctl handler of a driver.
+ * The passed buffer should have been verified.
+ * This function calls buf_prepare callback in the driver (if provided),
+ * in which driver-specific buffer initialization can be performed,
+ *
+ * The return values from this function are intended to be directly returned
+ * from vidioc_prepare_buf handler in driver.
+ */
 int vb2_core_prepare_buf(struct vb2_queue *q, unsigned int index, void *pb);
+
+/**
+ * vb2_core_qbuf() - Queue a buffer from userspace
+ * @q:          videobuf2 queue
+ * @index:      id number of the buffer
+ * @pb:         buffer structure passed from userspace to vidioc_qbuf handler
+ *              in driver
+ *
+ * Should be called from vidioc_qbuf ioctl handler of a driver.
+ * The passed buffer should have been verified.
+ * This function:
+ * 1) if necessary, calls buf_prepare callback in the driver (if provided), in
+ *    which driver-specific buffer initialization can be performed,
+ * 2) if streaming is on, queues the buffer in driver by the means of buf_queue
+ *    callback for processing.
+ *
+ * The return values from this function are intended to be directly returned
+ * from vidioc_qbuf handler in driver.
+ */
 int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb);
+
+/**
+ * vb2_core_dqbuf() - Dequeue a buffer to the userspace
+ * @q:          videobuf2 queue
+ * @pindex:     pointer to the buffer index. May be NULL
+ * @pb:         buffer structure passed from userspace to vidioc_dqbuf handler
+ *              in driver
+ * @nonblocking: if true, this call will not sleep waiting for a buffer if no
+ *               buffers ready for dequeuing are present. Normally the driver
+ *               would be passing (file->f_flags & O_NONBLOCK) here
+ *
+ * Should be called from vidioc_dqbuf ioctl handler of a driver.
+ * The passed buffer should have been verified.
+ * This function:
+ * 1) calls buf_finish callback in the driver (if provided), in which
+ *    driver can perform any additional operations that may be required before
+ *    returning the buffer to userspace, such as cache sync,
+ * 2) the buffer struct members are filled with relevant information for
+ *    the userspace.
+ *
+ * The return values from this function are intended to be directly returned
+ * from vidioc_dqbuf handler in driver.
+ */
 int vb2_core_dqbuf(struct vb2_queue *q, unsigned int *pindex, void *pb,
                    bool nonblocking);
 
 int vb2_core_streamon(struct vb2_queue *q, unsigned int type);
 int vb2_core_streamoff(struct vb2_queue *q, unsigned int type);
 
+/**
+ * vb2_core_expbuf() - Export a buffer as a file descriptor
+ * @q:          videobuf2 queue
+ * @fd:         file descriptor associated with DMABUF (set by driver) *
+ * @type:       buffer type
+ * @index:      id number of the buffer
+ * @plane:      index of the plane to be exported, 0 for single plane queues
+ * @flags:      flags for newly created file, currently only O_CLOEXEC is
+ *              supported, refer to manual of open syscall for more details
+ *
+ * The return values from this function are intended to be directly returned
+ * from vidioc_expbuf handler in driver.
+ */
 int vb2_core_expbuf(struct vb2_queue *q, int *fd, unsigned int type,
                 unsigned int index, unsigned int plane, unsigned int flags);
 
+/**
+ * vb2_core_queue_init() - initialize a videobuf2 queue
+ * @q:          videobuf2 queue; this structure should be allocated in driver
+ *
+ * The vb2_queue structure should be allocated by the driver. The driver is
+ * responsible of clearing it's content and setting initial values for some
+ * required entries before calling this function.
+ * q->ops, q->mem_ops, q->type and q->io_modes are mandatory. Please refer
+ * to the struct vb2_queue description in include/media/videobuf2-core.h
+ * for more information.
+ */
 int vb2_core_queue_init(struct vb2_queue *q);
+
+/**
+ * vb2_core_queue_release() - stop streaming, release the queue and free memory
+ * @q:          videobuf2 queue
+ *
+ * This function stops streaming and performs necessary clean ups, including
+ * freeing video buffer memory. The driver is responsible for freeing
+ * the vb2_queue structure itself.
+ */
 void vb2_core_queue_release(struct vb2_queue *q);
 
+/**
+ * vb2_queue_error() - signal a fatal error on the queue
+ * @q:          videobuf2 queue
+ *
+ * Flag that a fatal unrecoverable error has occurred and wake up all processes
+ * waiting on the queue. Polling will now set POLLERR and queuing and dequeuing
+ * buffers will return -EIO.
+ *
+ * The error flag will be cleared when cancelling the queue, either from
+ * vb2_streamoff or vb2_queue_release. Drivers should thus not call this
+ * function before starting the stream, otherwise the error flag will remain set
+ * until the queue is released when closing the device node.
+ */
 void vb2_queue_error(struct vb2_queue *q);
 
+/**
+ * vb2_mmap() - map video buffers into application address space
+ * @q:          videobuf2 queue
+ * @vma:        vma passed to the mmap file operation handler in the driver
+ *
+ * Should be called from mmap file operation handler of a driver.
+ * This function maps one plane of one of the available video buffers to
+ * userspace. To map whole video memory allocated on reqbufs, this function
+ * has to be called once per each plane per each buffer previously allocated.
+ *
+ * When the userspace application calls mmap, it passes to it an offset returned
+ * to it earlier by the means of vidioc_querybuf handler. That offset acts as
+ * a "cookie", which is then used to identify the plane to be mapped.
+ * This function finds a plane with a matching offset and a mapping is performed
+ * by the means of a provided memory operation.
+ *
+ * The return values from this function are intended to be directly returned
+ * from the mmap handler in driver.
+ */
 int vb2_mmap(struct vb2_queue *q, struct vm_area_struct *vma);
 #ifndef CONFIG_MMU
 unsigned long vb2_get_unmapped_area(struct vb2_queue *q,
@@ -573,6 +812,23 @@ unsigned long vb2_get_unmapped_area(struct vb2_queue *q,
                                     unsigned long pgoff,
                                     unsigned long flags);
 #endif
+
+/**
+ * vb2_core_poll() - implements poll userspace operation
+ * @q:          videobuf2 queue
+ * @file:       file argument passed to the poll file operation handler
+ * @wait:       wait argument passed to the poll file operation handler
+ *
+ * This function implements poll file operation handler for a driver.
+ * For CAPTURE queues, if a buffer is ready to be dequeued, the userspace will
+ * be informed that the file descriptor of a video device is available for
+ * reading.
+ * For OUTPUT queues, if a buffer is ready to be dequeued, the file descriptor
+ * will be reported as available for writing.
+ *
+ * The return values from this function are intended to be directly returned
+ * from poll handler in driver.
+ */
 unsigned int vb2_core_poll(struct vb2_queue *q, struct file *file,
                 poll_table *wait);
 size_t vb2_read(struct vb2_queue *q, char __user *data, size_t count,
@@ -717,7 +973,20 @@ static inline void vb2_clear_last_buffer_dequeued(struct vb2_queue *q)
  * The following functions are not part of the vb2 core API, but are useful
  * functions for videobuf2-*.
  */
+
+/**
+ * vb2_buffer_in_use() - return true if the buffer is in use and
+ * the queue cannot be freed (by the means of REQBUFS(0)) call
+ *
+ * @vb:         buffer for which plane size should be returned
+ * @q:          videobuf queue
+ */
 bool vb2_buffer_in_use(struct vb2_queue *q, struct vb2_buffer *vb);
+
+/**
+ * vb2_verify_memory_type() - Check whether the memory type and buffer type
+ * passed to a buffer operation are compatible with the queue.
+ */
 int vb2_verify_memory_type(struct vb2_queue *q,
                 enum vb2_memory memory, unsigned int type);
 #endif /* _MEDIA_VIDEOBUF2_CORE_H */