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 /*
  * videobuf2-core.h - Video Buffer 2 Core Framework
  *
  * Copyright (C) 2010 Samsung Electronics
  *
  * Author: Pawel Osciak <pawel@osciak.com>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation.
  */
 #ifndef _MEDIA_VIDEOBUF2_CORE_H
 #define _MEDIA_VIDEOBUF2_CORE_H
 
 #include <linux/mm_types.h>
 #include <linux/mutex.h>
 #include <linux/poll.h>
 #include <linux/dma-buf.h>
 #include <linux/bitops.h>
 #include <media/media-request.h>
 #include <media/frame_vector.h>
 
 #define VB2_MAX_FRAME   (32)
 #define VB2_MAX_PLANES  (8)
 
 /**
  * enum vb2_memory - type of memory model used to make the buffers visible
  *  on userspace.
  *
  * @VB2_MEMORY_UNKNOWN: Buffer status is unknown or it is not used yet on
  *          userspace.
  * @VB2_MEMORY_MMAP:    The buffers are allocated by the Kernel and it is
  *          memory mapped via mmap() ioctl. This model is
  *          also used when the user is using the buffers via
  *          read() or write() system calls.
  * @VB2_MEMORY_USERPTR: The buffers was allocated in userspace and it is
  *          memory mapped via mmap() ioctl.
  * @VB2_MEMORY_DMABUF:  The buffers are passed to userspace via DMA buffer.
  */
 enum vb2_memory {
     VB2_MEMORY_UNKNOWN  = 0,
     VB2_MEMORY_MMAP     = 1,
     VB2_MEMORY_USERPTR  = 2,
     VB2_MEMORY_DMABUF   = 4,
 };
 
 struct vb2_fileio_data;
 struct vb2_threadio_data;
 struct vb2_buffer;
 
 /**
  * struct vb2_mem_ops - memory handling/memory allocator operations.
  * @alloc:  allocate video memory and, optionally, allocator private data,
  *      return ERR_PTR() on failure or a pointer to allocator private,
  *      per-buffer data on success; the returned private structure
  *      will then be passed as @buf_priv argument to other ops in this
  *      structure. The size argument to this function shall be
  *      *page aligned*.
  * @put:    inform the allocator that the buffer will no longer be used;
  *      usually will result in the allocator freeing the buffer (if
  *      no other users of this buffer are present); the @buf_priv
  *      argument is the allocator private per-buffer structure
  *      previously returned from the alloc callback.
  * @get_dmabuf: acquire userspace memory for a hardware operation; used for
  *       DMABUF memory types.
  * @get_userptr: acquire userspace memory for a hardware operation; used for
  *       USERPTR memory types; vaddr is the address passed to the
  *       videobuf layer when queuing a video buffer of USERPTR type;
  *       should return an allocator private per-buffer structure
  *       associated with the buffer on success, ERR_PTR() on failure;
  *       the returned private structure will then be passed as @buf_priv
  *       argument to other ops in this structure.
  * @put_userptr: inform the allocator that a USERPTR buffer will no longer
  *       be used.
  * @attach_dmabuf: attach a shared &struct dma_buf for a hardware operation;
  *         used for DMABUF memory types; dev is the alloc device
  *         dbuf is the shared dma_buf; returns ERR_PTR() on failure;
  *         allocator private per-buffer structure on success;
  *         this needs to be used for further accesses to the buffer.
  * @detach_dmabuf: inform the exporter of the buffer that the current DMABUF
  *         buffer is no longer used; the @buf_priv argument is the
  *         allocator private per-buffer structure previously returned
  *         from the attach_dmabuf callback.
  * @map_dmabuf: request for access to the dmabuf from allocator; the allocator
  *      of dmabuf is informed that this driver is going to use the
  *      dmabuf.
  * @unmap_dmabuf: releases access control to the dmabuf - allocator is notified
  *        that this driver is done using the dmabuf for now.
  * @prepare:    called every time the buffer is passed from userspace to the
  *      driver, useful for cache synchronisation, optional.
  * @finish: called every time the buffer is passed back from the driver
  *      to the userspace, also optional.
  * @vaddr:  return a kernel virtual address to a given memory buffer
  *      associated with the passed private structure or NULL if no
  *      such mapping exists.
  * @cookie: return allocator specific cookie for a given memory buffer
  *      associated with the passed private structure or NULL if not
  *      available.
  * @num_users:  return the current number of users of a memory buffer;
  *      return 1 if the videobuf layer (or actually the driver using
  *      it) is the only user.
  * @mmap:   setup a userspace mapping for a given memory buffer under
  *      the provided virtual memory region.
  *
  * Those operations are used by the videobuf2 core to implement the memory
  * handling/memory allocators for each type of supported streaming I/O method.
  *
  * .. note::
  *    #) Required ops for USERPTR types: get_userptr, put_userptr.
  *
  *    #) Required ops for MMAP types: alloc, put, num_users, mmap.
  *
  *    #) Required ops for read/write access types: alloc, put, num_users, vaddr.
  *
  *    #) Required ops for DMABUF types: attach_dmabuf, detach_dmabuf,
  *       map_dmabuf, unmap_dmabuf.
  */
 struct vb2_mem_ops {
     void        *(*alloc)(struct vb2_buffer *vb,
                   struct device *dev,
                   unsigned long size);
     void        (*put)(void *buf_priv);
     struct dma_buf *(*get_dmabuf)(struct vb2_buffer *vb,
                       void *buf_priv,
                       unsigned long flags);
 
     void        *(*get_userptr)(struct vb2_buffer *vb,
                     struct device *dev,
                     unsigned long vaddr,
                     unsigned long size);
     void        (*put_userptr)(void *buf_priv);
 
     void        (*prepare)(void *buf_priv);
     void        (*finish)(void *buf_priv);
 
     void        *(*attach_dmabuf)(struct vb2_buffer *vb,
                       struct device *dev,
                       struct dma_buf *dbuf,
                       unsigned long size);
     void        (*detach_dmabuf)(void *buf_priv);
     int     (*map_dmabuf)(void *buf_priv);
     void        (*unmap_dmabuf)(void *buf_priv);
 
     void        *(*vaddr)(struct vb2_buffer *vb, void *buf_priv);
     void        *(*cookie)(struct vb2_buffer *vb, void *buf_priv);
 
     unsigned int    (*num_users)(void *buf_priv);
 
     int     (*mmap)(void *buf_priv, struct vm_area_struct *vma);
 };
 
 /**
  * struct vb2_plane - plane information.
  * @mem_priv:   private data with this plane.
  * @dbuf:   dma_buf - shared buffer object.
  * @dbuf_mapped:    flag to show whether dbuf is mapped or not
  * @bytesused:  number of bytes occupied by data in the plane (payload).
  * @length: size of this plane (NOT the payload) in bytes. The maximum
  *      valid size is MAX_UINT - PAGE_SIZE.
  * @min_length: minimum required size of this plane (NOT the payload) in bytes.
  *      @length is always greater or equal to @min_length, and like
  *      @length, it is limited to MAX_UINT - PAGE_SIZE.
  * @m:      Union with memtype-specific data.
  * @m.offset:   when memory in the associated struct vb2_buffer is
  *      %VB2_MEMORY_MMAP, equals the offset from the start of
  *      the device memory for this plane (or is a "cookie" that
  *      should be passed to mmap() called on the video node).
  * @m.userptr:  when memory is %VB2_MEMORY_USERPTR, a userspace pointer
  *      pointing to this plane.
  * @m.fd:   when memory is %VB2_MEMORY_DMABUF, a userspace file
  *      descriptor associated with this plane.
  * @data_offset:    offset in the plane to the start of data; usually 0,
  *      unless there is a header in front of the data.
  *
  * Should contain enough information to be able to cover all the fields
  * of &struct v4l2_plane at videodev2.h.
  */
 struct vb2_plane {
     void            *mem_priv;
     struct dma_buf      *dbuf;
     unsigned int        dbuf_mapped;
     unsigned int        bytesused;
     unsigned int        length;
     unsigned int        min_length;
     union {
         unsigned int    offset;
         unsigned long   userptr;
         int     fd;
     } m;
     unsigned int        data_offset;
 };
 
 /**
  * enum vb2_io_modes - queue access methods.
  * @VB2_MMAP:       driver supports MMAP with streaming API.
  * @VB2_USERPTR:    driver supports USERPTR with streaming API.
  * @VB2_READ:       driver supports read() style access.
  * @VB2_WRITE:      driver supports write() style access.
  * @VB2_DMABUF:     driver supports DMABUF with streaming API.
  */
 enum vb2_io_modes {
     VB2_MMAP    = BIT(0),
     VB2_USERPTR = BIT(1),
     VB2_READ    = BIT(2),
     VB2_WRITE   = BIT(3),
     VB2_DMABUF  = BIT(4),
 };
 
 /**
  * enum vb2_buffer_state - current video buffer state.
  * @VB2_BUF_STATE_DEQUEUED: buffer under userspace control.
  * @VB2_BUF_STATE_IN_REQUEST:   buffer is queued in media request.
  * @VB2_BUF_STATE_PREPARING:    buffer is being prepared in videobuf.
  * @VB2_BUF_STATE_QUEUED:   buffer queued in videobuf, but not in driver.
  * @VB2_BUF_STATE_ACTIVE:   buffer queued in driver and possibly used
  *              in a hardware operation.
  * @VB2_BUF_STATE_DONE:     buffer returned from driver to videobuf, but
  *              not yet dequeued to userspace.
  * @VB2_BUF_STATE_ERROR:    same as above, but the operation on the buffer
  *              has ended with an error, which will be reported
  *              to the userspace when it is dequeued.
  */
 enum vb2_buffer_state {
     VB2_BUF_STATE_DEQUEUED,
     VB2_BUF_STATE_IN_REQUEST,
     VB2_BUF_STATE_PREPARING,
     VB2_BUF_STATE_QUEUED,
     VB2_BUF_STATE_ACTIVE,
     VB2_BUF_STATE_DONE,
     VB2_BUF_STATE_ERROR,
 };
 
 struct vb2_queue;
 
 /**
  * struct vb2_buffer - represents a video buffer.
  * @vb2_queue:      pointer to &struct vb2_queue with the queue to
  *          which this driver belongs.
  * @index:      id number of the buffer.
  * @type:       buffer type.
  * @memory:     the method, in which the actual data is passed.
  * @num_planes:     number of planes in the buffer
  *          on an internal driver queue.
  * @timestamp:      frame timestamp in ns.
  * @request:        the request this buffer is associated with.
  * @req_obj:        used to bind this buffer to a request. This
  *          request object has a refcount.
  */
 struct vb2_buffer {
     struct vb2_queue    *vb2_queue;
     unsigned int        index;
     unsigned int        type;
     unsigned int        memory;
     unsigned int        num_planes;
     u64         timestamp;
     struct media_request    *request;
     struct media_request_object req_obj;
 
     /* private: internal use only
      *
      * state:       current buffer state; do not change
      * synced:      this buffer has been synced for DMA, i.e. the
      *          'prepare' memop was called. It is cleared again
      *          after the 'finish' memop is called.
      * prepared:        this buffer has been prepared, i.e. the
      *          buf_prepare op was called. It is cleared again
      *          after the 'buf_finish' op is called.
      * copied_timestamp:    the timestamp of this capture buffer was copied
      *          from an output buffer.
      * skip_cache_sync_on_prepare: when set buffer's ->prepare() function
      *          skips cache sync/invalidation.
      * skip_cache_sync_on_finish: when set buffer's ->finish() function
      *          skips cache sync/invalidation.
      * queued_entry:    entry on the queued buffers list, which holds
      *          all buffers queued from userspace
      * done_entry:      entry on the list that stores all buffers ready
      *          to be dequeued to userspace
      * vb2_plane:       per-plane information; do not change
      */
     enum vb2_buffer_state   state;
     unsigned int        synced:1;
     unsigned int        prepared:1;
     unsigned int        copied_timestamp:1;
     unsigned int        skip_cache_sync_on_prepare:1;
     unsigned int        skip_cache_sync_on_finish:1;
 
     struct vb2_plane    planes[VB2_MAX_PLANES];
     struct list_head    queued_entry;
     struct list_head    done_entry;
 #ifdef CONFIG_VIDEO_ADV_DEBUG
     /*
      * Counters for how often these buffer-related ops are
      * called. Used to check for unbalanced ops.
      */
     u32     cnt_mem_alloc;
     u32     cnt_mem_put;
     u32     cnt_mem_get_dmabuf;
     u32     cnt_mem_get_userptr;
     u32     cnt_mem_put_userptr;
     u32     cnt_mem_prepare;
     u32     cnt_mem_finish;
     u32     cnt_mem_attach_dmabuf;
     u32     cnt_mem_detach_dmabuf;
     u32     cnt_mem_map_dmabuf;
     u32     cnt_mem_unmap_dmabuf;
     u32     cnt_mem_vaddr;
     u32     cnt_mem_cookie;
     u32     cnt_mem_num_users;
     u32     cnt_mem_mmap;
 
     u32     cnt_buf_out_validate;
     u32     cnt_buf_init;
     u32     cnt_buf_prepare;
     u32     cnt_buf_finish;
     u32     cnt_buf_cleanup;
     u32     cnt_buf_queue;
     u32     cnt_buf_request_complete;
 
     /* This counts the number of calls to vb2_buffer_done() */
     u32     cnt_buf_done;
 #endif
 };
 
 /**
  * struct vb2_ops - driver-specific callbacks.
  *
  * These operations are not called from interrupt context except where
  * mentioned specifically.
  *
  * @queue_setup:    called from VIDIOC_REQBUFS() and VIDIOC_CREATE_BUFS()
  *          handlers before memory allocation. It can be called
  *          twice: if the original number of requested buffers
  *          could not be allocated, then it will be called a
  *          second time with the actually allocated number of
  *          buffers to verify if that is OK.
  *          The driver should return the required number of buffers
  *          in \*num_buffers, the required number of planes per
  *          buffer in \*num_planes, the size of each plane should be
  *          set in the sizes\[\] array and optional per-plane
  *          allocator specific device in the alloc_devs\[\] array.
  *          When called from VIDIOC_REQBUFS(), \*num_planes == 0,
  *          the driver has to use the currently configured format to
  *          determine the plane sizes and \*num_buffers is the total
  *          number of buffers that are being allocated. When called
  *          from VIDIOC_CREATE_BUFS(), \*num_planes != 0 and it
  *          describes the requested number of planes and sizes\[\]
  *          contains the requested plane sizes. In this case
  *          \*num_buffers are being allocated additionally to
  *          q->num_buffers. If either \*num_planes or the requested
  *          sizes are invalid callback must return %-EINVAL.
  * @wait_prepare:   release any locks taken while calling vb2 functions;
  *          it is called before an ioctl needs to wait for a new
  *          buffer to arrive; required to avoid a deadlock in
  *          blocking access type.
  * @wait_finish:    reacquire all locks released in the previous callback;
  *          required to continue operation after sleeping while
  *          waiting for a new buffer to arrive.
  * @buf_out_validate:   called when the output buffer is prepared or queued
  *          to a request; drivers can use this to validate
  *          userspace-provided information; this is required only
  *          for OUTPUT queues.
  * @buf_init:       called once after allocating a buffer (in MMAP case)
  *          or after acquiring a new USERPTR buffer; drivers may
  *          perform additional buffer-related initialization;
  *          initialization failure (return != 0) will prevent
  *          queue setup from completing successfully; optional.
  * @buf_prepare:    called every time the buffer is queued from userspace
  *          and from the VIDIOC_PREPARE_BUF() ioctl; drivers may
  *          perform any initialization required before each
  *          hardware operation in this callback; drivers can
  *          access/modify the buffer here as it is still synced for
  *          the CPU; drivers that support VIDIOC_CREATE_BUFS() must
  *          also validate the buffer size; if an error is returned,
  *          the buffer will not be queued in driver; optional.
  * @buf_finish:     called before every dequeue of the buffer back to
  *          userspace; the buffer is synced for the CPU, so drivers
  *          can access/modify the buffer contents; drivers may
  *          perform any operations required before userspace
  *          accesses the buffer; optional. The buffer state can be
  *          one of the following: %DONE and %ERROR occur while
  *          streaming is in progress, and the %PREPARED state occurs
  *          when the queue has been canceled and all pending
  *          buffers are being returned to their default %DEQUEUED
  *          state. Typically you only have to do something if the
  *          state is %VB2_BUF_STATE_DONE, since in all other cases
  *          the buffer contents will be ignored anyway.
  * @buf_cleanup:    called once before the buffer is freed; drivers may
  *          perform any additional cleanup; optional.
  * @start_streaming:    called once to enter 'streaming' state; the driver may
  *          receive buffers with @buf_queue callback
  *          before @start_streaming is called; the driver gets the
  *          number of already queued buffers in count parameter;
  *          driver can return an error if hardware fails, in that
  *          case all buffers that have been already given by
  *          the @buf_queue callback are to be returned by the driver
  *          by calling vb2_buffer_done() with %VB2_BUF_STATE_QUEUED.
  *          If you need a minimum number of buffers before you can
  *          start streaming, then set
  *          &vb2_queue->min_buffers_needed. If that is non-zero
  *          then @start_streaming won't be called until at least
  *          that many buffers have been queued up by userspace.
  * @stop_streaming: called when 'streaming' state must be disabled; driver
  *          should stop any DMA transactions or wait until they
  *          finish and give back all buffers it got from &buf_queue
  *          callback by calling vb2_buffer_done() with either
  *          %VB2_BUF_STATE_DONE or %VB2_BUF_STATE_ERROR; may use
  *          vb2_wait_for_all_buffers() function
  * @buf_queue:      passes buffer vb to the driver; driver may start
  *          hardware operation on this buffer; driver should give
  *          the buffer back by calling vb2_buffer_done() function;
  *          it is always called after calling VIDIOC_STREAMON()
  *          ioctl; might be called before @start_streaming callback
  *          if user pre-queued buffers before calling
  *          VIDIOC_STREAMON().
  * @buf_request_complete: a buffer that was never queued to the driver but is
  *          associated with a queued request was canceled.
  *          The driver will have to mark associated objects in the
  *          request as completed; required if requests are
  *          supported.
  */
 struct vb2_ops {
     int (*queue_setup)(struct vb2_queue *q,
                unsigned int *num_buffers, unsigned int *num_planes,
                unsigned int sizes[], struct device *alloc_devs[]);
 
     void (*wait_prepare)(struct vb2_queue *q);
     void (*wait_finish)(struct vb2_queue *q);
 
     int (*buf_out_validate)(struct vb2_buffer *vb);
     int (*buf_init)(struct vb2_buffer *vb);
     int (*buf_prepare)(struct vb2_buffer *vb);
     void (*buf_finish)(struct vb2_buffer *vb);
     void (*buf_cleanup)(struct vb2_buffer *vb);
 
     int (*start_streaming)(struct vb2_queue *q, unsigned int count);
     void (*stop_streaming)(struct vb2_queue *q);
 
     void (*buf_queue)(struct vb2_buffer *vb);
 
     void (*buf_request_complete)(struct vb2_buffer *vb);
 };
 
 /**
  * struct vb2_buf_ops - driver-specific callbacks.
  *
  * @verify_planes_array: Verify that a given user space structure contains
  *          enough planes for the buffer. This is called
  *          for each dequeued buffer.
  * @init_buffer:    given a &vb2_buffer initialize the extra data after
  *          struct vb2_buffer.
  *          For V4L2 this is a &struct vb2_v4l2_buffer.
  * @fill_user_buffer:   given a &vb2_buffer fill in the userspace structure.
  *          For V4L2 this is a &struct v4l2_buffer.
  * @fill_vb2_buffer:    given a userspace structure, fill in the &vb2_buffer.
  *          If the userspace structure is invalid, then this op
  *          will return an error.
  * @copy_timestamp: copy the timestamp from a userspace structure to
  *          the &struct vb2_buffer.
  */
 struct vb2_buf_ops {
     int (*verify_planes_array)(struct vb2_buffer *vb, const void *pb);
     void (*init_buffer)(struct vb2_buffer *vb);
     void (*fill_user_buffer)(struct vb2_buffer *vb, void *pb);
     int (*fill_vb2_buffer)(struct vb2_buffer *vb, struct vb2_plane *planes);
     void (*copy_timestamp)(struct vb2_buffer *vb, const void *pb);
 };
 
 /**
  * struct vb2_queue - a videobuf queue.
  *
  * @type:   private buffer type whose content is defined by the vb2-core
  *      caller. For example, for V4L2, it should match
  *      the types defined on &enum v4l2_buf_type.
  * @io_modes:   supported io methods (see &enum vb2_io_modes).
  * @alloc_devs: &struct device memory type/allocator-specific per-plane device
  * @dev:    device to use for the default allocation context if the driver
  *      doesn't fill in the @alloc_devs array.
  * @dma_attrs:  DMA attributes to use for the DMA.
  * @bidirectional: when this flag is set the DMA direction for the buffers of
  *      this queue will be overridden with %DMA_BIDIRECTIONAL direction.
  *      This is useful in cases where the hardware (firmware) writes to
  *      a buffer which is mapped as read (%DMA_TO_DEVICE), or reads from
  *      buffer which is mapped for write (%DMA_FROM_DEVICE) in order
  *      to satisfy some internal hardware restrictions or adds a padding
  *      needed by the processing algorithm. In case the DMA mapping is
  *      not bidirectional but the hardware (firmware) trying to access
  *      the buffer (in the opposite direction) this could lead to an
  *      IOMMU protection faults.
  * @fileio_read_once:       report EOF after reading the first buffer
  * @fileio_write_immediately:   queue buffer after each write() call
  * @allow_zero_bytesused:   allow bytesused == 0 to be passed to the driver
  * @quirk_poll_must_check_waiting_for_buffers: Return %EPOLLERR at poll when QBUF
  *              has not been called. This is a vb1 idiom that has been adopted
  *              also by vb2.
  * @supports_requests: this queue supports the Request API.
  * @requires_requests: this queue requires the Request API. If this is set to 1,
  *      then supports_requests must be set to 1 as well.
  * @uses_qbuf:  qbuf was used directly for this queue. Set to 1 the first
  *      time this is called. Set to 0 when the queue is canceled.
  *      If this is 1, then you cannot queue buffers from a request.
  * @uses_requests: requests are used for this queue. Set to 1 the first time
  *      a request is queued. Set to 0 when the queue is canceled.
  *      If this is 1, then you cannot queue buffers directly.
  * @allow_cache_hints: when set user-space can pass cache management hints in
  *      order to skip cache flush/invalidation on ->prepare() or/and
  *      ->finish().
  * @non_coherent_mem: when set queue will attempt to allocate buffers using
  *      non-coherent memory.
  * @lock:   pointer to a mutex that protects the &struct vb2_queue. The
  *      driver can set this to a mutex to let the v4l2 core serialize
  *      the queuing ioctls. If the driver wants to handle locking
  *      itself, then this should be set to NULL. This lock is not used
  *      by the videobuf2 core API.
  * @owner:  The filehandle that 'owns' the buffers, i.e. the filehandle
  *      that called reqbufs, create_buffers or started fileio.
  *      This field is not used by the videobuf2 core API, but it allows
  *      drivers to easily associate an owner filehandle with the queue.
  * @ops:    driver-specific callbacks
  * @mem_ops:    memory allocator specific callbacks
  * @buf_ops:    callbacks to deliver buffer information.
  *      between user-space and kernel-space.
  * @drv_priv:   driver private data.
  * @subsystem_flags: Flags specific to the subsystem (V4L2/DVB/etc.). Not used
  *      by the vb2 core.
  * @buf_struct_size: size of the driver-specific buffer structure;
  *      "0" indicates the driver doesn't want to use a custom buffer
  *      structure type. In that case a subsystem-specific struct
  *      will be used (in the case of V4L2 that is
  *      ``sizeof(struct vb2_v4l2_buffer)``). The first field of the
  *      driver-specific buffer structure must be the subsystem-specific
  *      struct (vb2_v4l2_buffer in the case of V4L2).
  * @timestamp_flags: Timestamp flags; ``V4L2_BUF_FLAG_TIMESTAMP_*`` and
  *      ``V4L2_BUF_FLAG_TSTAMP_SRC_*``
  * @gfp_flags:  additional gfp flags used when allocating the buffers.
  *      Typically this is 0, but it may be e.g. %GFP_DMA or %__GFP_DMA32
  *      to force the buffer allocation to a specific memory zone.
  * @min_buffers_needed: the minimum number of buffers needed before
  *      @start_streaming can be called. Used when a DMA engine
  *      cannot be started unless at least this number of buffers
  *      have been queued into the driver.
  */
 /*
  * Private elements (won't appear at the uAPI book):
  * @mmap_lock:  private mutex used when buffers are allocated/freed/mmapped
  * @memory: current memory type used
  * @dma_dir:    DMA mapping direction.
  * @bufs:   videobuf buffer structures
  * @num_buffers: number of allocated/used buffers
  * @queued_list: list of buffers currently queued from userspace
  * @queued_count: number of buffers queued and ready for streaming.
  * @owned_by_drv_count: number of buffers owned by the driver
  * @done_list:  list of buffers ready to be dequeued to userspace
  * @done_lock:  lock to protect done_list list
  * @done_wq:    waitqueue for processes waiting for buffers ready to be dequeued
  * @streaming:  current streaming state
  * @start_streaming_called: @start_streaming was called successfully and we
  *      started streaming.
  * @error:  a fatal error occurred on the queue
  * @waiting_for_buffers: used in poll() to check if vb2 is still waiting for
  *      buffers. Only set for capture queues if qbuf has not yet been
  *      called since poll() needs to return %EPOLLERR in that situation.
  * @is_multiplanar: set if buffer type is multiplanar
  * @is_output:  set if buffer type is output
  * @copy_timestamp: set if vb2-core should set timestamps
  * @last_buffer_dequeued: used in poll() and DQBUF to immediately return if the
  *      last decoded buffer was already dequeued. Set for capture queues
  *      when a buffer with the %V4L2_BUF_FLAG_LAST is dequeued.
  * @fileio: file io emulator internal data, used only if emulator is active
  * @threadio:   thread io internal data, used only if thread is active
  * @name:   queue name, used for logging purpose. Initialized automatically
  *      if left empty by drivers.
  */
 struct vb2_queue {
     unsigned int            type;
     unsigned int            io_modes;
     struct device           *dev;
     unsigned long           dma_attrs;
     unsigned int            bidirectional:1;
     unsigned int            fileio_read_once:1;
     unsigned int            fileio_write_immediately:1;
     unsigned int            allow_zero_bytesused:1;
     unsigned int           quirk_poll_must_check_waiting_for_buffers:1;
     unsigned int            supports_requests:1;
     unsigned int            requires_requests:1;
     unsigned int            uses_qbuf:1;
     unsigned int            uses_requests:1;
     unsigned int            allow_cache_hints:1;
     unsigned int            non_coherent_mem:1;
 
     struct mutex            *lock;
     void                *owner;
 
     const struct vb2_ops        *ops;
     const struct vb2_mem_ops    *mem_ops;
     const struct vb2_buf_ops    *buf_ops;
 
     void                *drv_priv;
     u32             subsystem_flags;
     unsigned int            buf_struct_size;
     u32             timestamp_flags;
     gfp_t               gfp_flags;
     u32             min_buffers_needed;
 
     struct device           *alloc_devs[VB2_MAX_PLANES];
 
     /* private: internal use only */
     struct mutex            mmap_lock;
     unsigned int            memory;
     enum dma_data_direction     dma_dir;
     struct vb2_buffer       *bufs[VB2_MAX_FRAME];
     unsigned int            num_buffers;
 
     struct list_head        queued_list;
     unsigned int            queued_count;
 
     atomic_t            owned_by_drv_count;
     struct list_head        done_list;
     spinlock_t          done_lock;
     wait_queue_head_t       done_wq;
 
     unsigned int            streaming:1;
     unsigned int            start_streaming_called:1;
     unsigned int            error:1;
     unsigned int            waiting_for_buffers:1;
     unsigned int            waiting_in_dqbuf:1;
     unsigned int            is_multiplanar:1;
     unsigned int            is_output:1;
     unsigned int            copy_timestamp:1;
     unsigned int            last_buffer_dequeued:1;
 
     struct vb2_fileio_data      *fileio;
     struct vb2_threadio_data    *threadio;
 
     char                name[32];
 
 #ifdef CONFIG_VIDEO_ADV_DEBUG
     /*
      * Counters for how often these queue-related ops are
      * called. Used to check for unbalanced ops.
      */
     u32             cnt_queue_setup;
     u32             cnt_wait_prepare;
     u32             cnt_wait_finish;
     u32             cnt_start_streaming;
     u32             cnt_stop_streaming;
 #endif
 };
 
 /**
  * vb2_queue_allows_cache_hints() - Return true if the queue allows cache
  * and memory consistency hints.
  *
  * @q:      pointer to &struct vb2_queue with videobuf2 queue
  */
 static inline bool vb2_queue_allows_cache_hints(struct vb2_queue *q)
 {
     return q->allow_cache_hints && q->memory == VB2_MEMORY_MMAP;
 }
 
 /**
  * vb2_plane_vaddr() - Return a kernel virtual address of a given plane.
  * @vb:     pointer to &struct 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:     pointer to &struct 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:     pointer to &struct vb2_buffer to be used.
  * @state:  state of the buffer, as defined by &enum vb2_buffer_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.
  *
  * 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 &vb2_ops->buf_queue callback. Only buffers previously queued
  * to the driver by &vb2_ops->buf_queue can be passed to this function.
  *
  * While streaming a buffer can only be returned in state DONE or ERROR.
  * The &vb2_ops->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 to put them back into the queue.
  */
 void vb2_buffer_done(struct vb2_buffer *vb, enum vb2_buffer_state state);
 
 /**
  * vb2_discard_done() - discard all buffers marked as DONE.
  * @q:      pointer to &struct vb2_queue with 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:      pointer to &struct vb2_queue with videobuf2 queue.
  *
  * This function will wait until all buffers that have been given to the driver
  * by &vb2_ops->buf_queue are given back to vb2 with vb2_buffer_done(). It
  * doesn't call &vb2_ops->wait_prepare/&vb2_ops->wait_finish pair.
  * It is intended to be called with all locks taken, for example from
  * &vb2_ops->stop_streaming callback.
  */
 int vb2_wait_for_all_buffers(struct vb2_queue *q);
 
 /**
  * vb2_core_querybuf() - query video buffer information.
  * @q:      pointer to &struct vb2_queue with videobuf2 queue.
  * @index:  id number of the buffer.
  * @pb:     buffer struct passed from userspace.
  *
  * Videobuf2 core helper to implement VIDIOC_QUERYBUF() operation. It is called
  * internally by VB2 by an API-specific handler, like ``videobuf2-v4l2.h``.
  *
  * The passed buffer should have been verified.
  *
  * This function fills the relevant information for the userspace.
  *
  * Return: returns zero on success; an error code otherwise.
  */
 void vb2_core_querybuf(struct vb2_queue *q, unsigned int index, void *pb);
 
 /**
  * vb2_core_reqbufs() - Initiate streaming.
  * @q:      pointer to &struct vb2_queue with videobuf2 queue.
  * @memory: memory type, as defined by &enum vb2_memory.
  * @flags:  auxiliary queue/buffer management flags. Currently, the only
  *      used flag is %V4L2_MEMORY_FLAG_NON_COHERENT.
  * @count:  requested buffer count.
  *
  * Videobuf2 core helper to implement VIDIOC_REQBUF() operation. It is called
  * internally by VB2 by an API-specific handler, like ``videobuf2-v4l2.h``.
  *
  * This function:
  *
  * #) verifies streaming parameters passed from the userspace;
  * #) sets up the queue;
  * #) negotiates number of buffers and planes per buffer with the driver
  *    to be used during streaming;
  * #) allocates internal buffer structures (&struct vb2_buffer), according to
  *    the agreed parameters;
  * #) 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_core_reqbufs()
  * call and the queue is not busy, memory will be reallocated.
  *
  * Return: returns zero on success; an error code otherwise.
  */
 int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
              unsigned int flags, unsigned int *count);
 
 /**
  * vb2_core_create_bufs() - Allocate buffers and any required auxiliary structs
  * @q: pointer to &struct vb2_queue with videobuf2 queue.
  * @memory: memory type, as defined by &enum vb2_memory.
  * @flags: auxiliary queue/buffer management flags.
  * @count: requested buffer count.
  * @requested_planes: number of planes requested.
  * @requested_sizes: array with the size of the planes.
  *
  * Videobuf2 core helper to implement VIDIOC_CREATE_BUFS() operation. It is
  * called internally by VB2 by an API-specific handler, like
  * ``videobuf2-v4l2.h``.
  *
  * This function:
  *
  * #) verifies parameter sanity;
  * #) calls the &vb2_ops->queue_setup queue operation;
  * #) performs any necessary memory allocations.
  *
  * Return: returns zero on success; an error code otherwise.
  */
 int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
              unsigned int flags, unsigned int *count,
              unsigned int requested_planes,
              const unsigned int requested_sizes[]);
 
 /**
  * vb2_core_prepare_buf() - Pass ownership of a buffer from userspace
  *          to the kernel.
  * @q:      pointer to &struct vb2_queue with videobuf2 queue.
  * @index:  id number of the buffer.
  * @pb:     buffer structure passed from userspace to
  *      &v4l2_ioctl_ops->vidioc_prepare_buf handler in driver.
  *
  * Videobuf2 core helper to implement VIDIOC_PREPARE_BUF() operation. It is
  * called internally by VB2 by an API-specific handler, like
  * ``videobuf2-v4l2.h``.
  *
  * The passed buffer should have been verified.
  *
  * This function calls vb2_ops->buf_prepare callback in the driver
  * (if provided), in which driver-specific buffer initialization can
  * be performed.
  *
  * Return: returns zero on success; an error code otherwise.
  */
 int vb2_core_prepare_buf(struct vb2_queue *q, unsigned int index, void *pb);
 
 /**
  * vb2_core_qbuf() - Queue a buffer from userspace
  *
  * @q:      pointer to &struct vb2_queue with videobuf2 queue.
  * @index:  id number of the buffer
  * @pb:     buffer structure passed from userspace to
  *      v4l2_ioctl_ops->vidioc_qbuf handler in driver
  * @req:    pointer to &struct media_request, may be NULL.
  *
  * Videobuf2 core helper to implement VIDIOC_QBUF() operation. It is called
  * internally by VB2 by an API-specific handler, like ``videobuf2-v4l2.h``.
  *
  * This function:
  *
  * #) If @req is non-NULL, then the buffer will be bound to this
  *    media request and it returns. The buffer will be prepared and
  *    queued to the driver (i.e. the next two steps) when the request
  *    itself is queued.
  * #) if necessary, calls &vb2_ops->buf_prepare callback in the driver
  *    (if provided), in which driver-specific buffer initialization can
  *    be performed;
  * #) if streaming is on, queues the buffer in driver by the means of
  *    &vb2_ops->buf_queue callback for processing.
  *
  * Return: returns zero on success; an error code otherwise.
  */
 int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb,
           struct media_request *req);
 
 /**
  * vb2_core_dqbuf() - Dequeue a buffer to the userspace
  * @q:      pointer to &struct vb2_queue with videobuf2 queue
  * @pindex: pointer to the buffer index. May be NULL
  * @pb:     buffer structure passed from userspace to
  *      v4l2_ioctl_ops->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.
  *
  * Videobuf2 core helper to implement VIDIOC_DQBUF() operation. It is called
  * internally by VB2 by an API-specific handler, like ``videobuf2-v4l2.h``.
  *
  * This function:
  *
  * #) 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,
  * #) the buffer struct members are filled with relevant information for
  *    the userspace.
  *
  * Return: returns zero on success; an error code otherwise.
  */
 int vb2_core_dqbuf(struct vb2_queue *q, unsigned int *pindex, void *pb,
            bool nonblocking);
 
 /**
  * vb2_core_streamon() - Implements VB2 stream ON logic
  *
  * @q:      pointer to &struct vb2_queue with videobuf2 queue
  * @type:   type of the queue to be started.
  *      For V4L2, this is defined by &enum v4l2_buf_type type.
  *
  * Videobuf2 core helper to implement VIDIOC_STREAMON() operation. It is called
  * internally by VB2 by an API-specific handler, like ``videobuf2-v4l2.h``.
  *
  * Return: returns zero on success; an error code otherwise.
  */
 int vb2_core_streamon(struct vb2_queue *q, unsigned int type);
 
 /**
  * vb2_core_streamoff() - Implements VB2 stream OFF logic
  *
  * @q:      pointer to &struct vb2_queue with videobuf2 queue
  * @type:   type of the queue to be started.
  *      For V4L2, this is defined by &enum v4l2_buf_type type.
  *
  * Videobuf2 core helper to implement VIDIOC_STREAMOFF() operation. It is
  * called internally by VB2 by an API-specific handler, like
  * ``videobuf2-v4l2.h``.
  *
  * Return: returns zero on success; an error code otherwise.
  */
 int vb2_core_streamoff(struct vb2_queue *q, unsigned int type);
 
 /**
  * vb2_core_expbuf() - Export a buffer as a file descriptor.
  * @q:      pointer to &struct vb2_queue with videobuf2 queue.
  * @fd:     pointer to the 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:  file flags for newly created file, as defined at
  *      include/uapi/asm-generic/fcntl.h.
  *      Currently, the only used flag is %O_CLOEXEC.
  *      is supported, refer to manual of open syscall for more details.
  *
  *
  * Videobuf2 core helper to implement VIDIOC_EXPBUF() operation. It is called
  * internally by VB2 by an API-specific handler, like ``videobuf2-v4l2.h``.
  *
  * Return: returns zero on success; an error code otherwise.
  */
 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:      pointer to &struct vb2_queue with 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.
  *
  * .. note::
  *
  *    The following fields at @q should be set before calling this function:
  *    &vb2_queue->ops, &vb2_queue->mem_ops, &vb2_queue->type.
  */
 int vb2_core_queue_init(struct vb2_queue *q);
 
 /**
  * vb2_core_queue_release() - stop streaming, release the queue and free memory
  * @q:      pointer to &struct vb2_queue with videobuf2 queue.
  *
  * This function stops streaming and performs necessary clean ups, including
  * freeing video buffer memory. The driver is responsible for freeing
  * the &struct vb2_queue itself.
  */
 void vb2_core_queue_release(struct vb2_queue *q);
 
 /**
  * vb2_queue_error() - signal a fatal error on the queue
  * @q:      pointer to &struct vb2_queue with videobuf2 queue.
  *
  * Flag that a fatal unrecoverable error has occurred and wake up all processes
  * waiting on the queue. Polling will now set %EPOLLERR and queuing and dequeuing
  * buffers will return %-EIO.
  *
  * The error flag will be cleared when canceling 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:      pointer to &struct vb2_queue with videobuf2 queue.
  * @vma:    pointer to &struct vm_area_struct with the 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 &v4l2_ioctl_ops->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
 /**
  * vb2_get_unmapped_area - map video buffers into application address space.
  * @q:      pointer to &struct vb2_queue with videobuf2 queue.
  * @addr:   memory address.
  * @len:    buffer size.
  * @pgoff:  page offset.
  * @flags:  memory flags.
  *
  * This function is used in noMMU platforms to propose address mapping
  * for a given buffer. It's intended to be used as a handler for the
  * &file_operations->get_unmapped_area operation.
  *
  * This is called by the mmap() syscall routines will call this
  * to get a proposed address for the mapping, when ``!CONFIG_MMU``.
  */
 unsigned long vb2_get_unmapped_area(struct vb2_queue *q,
                     unsigned long addr,
                     unsigned long len,
                     unsigned long pgoff,
                     unsigned long flags);
 #endif
 
 /**
  * vb2_core_poll() - implements poll syscall() logic.
  * @q:      pointer to &struct vb2_queue with videobuf2 queue.
  * @file:   &struct file argument passed to the poll
  *      file operation handler.
  * @wait:   &poll_table 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.
  */
 __poll_t vb2_core_poll(struct vb2_queue *q, struct file *file,
                poll_table *wait);
 
 /**
  * vb2_read() - implements read() syscall logic.
  * @q:      pointer to &struct vb2_queue with videobuf2 queue.
  * @data:   pointed to target userspace buffer
  * @count:  number of bytes to read
  * @ppos:   file handle position tracking pointer
  * @nonblock:   mode selector (1 means blocking calls, 0 means nonblocking)
  */
 size_t vb2_read(struct vb2_queue *q, char __user *data, size_t count,
         loff_t *ppos, int nonblock);
 /**
  * vb2_write() - implements write() syscall logic.
  * @q:      pointer to &struct vb2_queue with videobuf2 queue.
  * @data:   pointed to target userspace buffer
  * @count:  number of bytes to write
  * @ppos:   file handle position tracking pointer
  * @nonblock:   mode selector (1 means blocking calls, 0 means nonblocking)
  */
 size_t vb2_write(struct vb2_queue *q, const char __user *data, size_t count,
         loff_t *ppos, int nonblock);
 
 /**
  * typedef vb2_thread_fnc - callback function for use with vb2_thread.
  *
  * @vb: pointer to struct &vb2_buffer.
  * @priv: pointer to a private data.
  *
  * This is called whenever a buffer is dequeued in the thread.
  */
 typedef int (*vb2_thread_fnc)(struct vb2_buffer *vb, void *priv);
 
 /**
  * vb2_thread_start() - start a thread for the given queue.
  * @q:      pointer to &struct vb2_queue with videobuf2 queue.
  * @fnc:    &vb2_thread_fnc callback function.
  * @priv:   priv pointer passed to the callback function.
  * @thread_name:the name of the thread. This will be prefixed with "vb2-".
  *
  * This starts a thread that will queue and dequeue until an error occurs
  * or vb2_thread_stop() is called.
  *
  * .. attention::
  *
  *   This function should not be used for anything else but the videobuf2-dvb
  *   support. If you think you have another good use-case for this, then please
  *   contact the linux-media mailing list first.
  */
 int vb2_thread_start(struct vb2_queue *q, vb2_thread_fnc fnc, void *priv,
              const char *thread_name);
 
 /**
  * vb2_thread_stop() - stop the thread for the given queue.
  * @q:      pointer to &struct vb2_queue with videobuf2 queue.
  */
 int vb2_thread_stop(struct vb2_queue *q);
 
 /**
  * vb2_is_streaming() - return streaming status of the queue.
  * @q:      pointer to &struct vb2_queue with videobuf2 queue.
  */
 static inline bool vb2_is_streaming(struct vb2_queue *q)
 {
     return q->streaming;
 }
 
 /**
  * vb2_fileio_is_active() - return true if fileio is active.
  * @q:      pointer to &struct vb2_queue with videobuf2 queue.
  *
  * This returns true if read() or write() is used to stream the data
  * as opposed to stream I/O. This is almost never an important distinction,
  * except in rare cases. One such case is that using read() or write() to
  * stream a format using %V4L2_FIELD_ALTERNATE is not allowed since there
  * is no way you can pass the field information of each buffer to/from
  * userspace. A driver that supports this field format should check for
  * this in the &vb2_ops->queue_setup op and reject it if this function returns
  * true.
  */
 static inline bool vb2_fileio_is_active(struct vb2_queue *q)
 {
     return q->fileio;
 }
 
 /**
  * vb2_is_busy() - return busy status of the queue.
  * @q:      pointer to &struct vb2_queue with videobuf2 queue.
  *
  * This function checks if queue has any buffers allocated.
  */
 static inline bool vb2_is_busy(struct vb2_queue *q)
 {
     return (q->num_buffers > 0);
 }
 
 /**
  * vb2_get_drv_priv() - return driver private data associated with the queue.
  * @q:      pointer to &struct vb2_queue with videobuf2 queue.
  */
 static inline void *vb2_get_drv_priv(struct vb2_queue *q)
 {
     return q->drv_priv;
 }
 
 /**
  * vb2_set_plane_payload() - set bytesused for the plane @plane_no.
  * @vb:     pointer to &struct vb2_buffer to which the plane in
  *      question belongs to.
  * @plane_no:   plane number for which payload should be set.
  * @size:   payload in bytes.
  */
 static inline void vb2_set_plane_payload(struct vb2_buffer *vb,
                  unsigned int plane_no, unsigned long size)
 {
     /*
      * size must never be larger than the buffer length, so
      * warn and clamp to the buffer length if that's the case.
      */
     if (plane_no < vb->num_planes) {
         if (WARN_ON_ONCE(size > vb->planes[plane_no].length))
             size = vb->planes[plane_no].length;
         vb->planes[plane_no].bytesused = size;
     }
 }
 
 /**
  * vb2_get_plane_payload() - get bytesused for the plane plane_no
  * @vb:     pointer to &struct vb2_buffer to which the plane in
  *      question belongs to.
  * @plane_no:   plane number for which payload should be set.
  */
 static inline unsigned long vb2_get_plane_payload(struct vb2_buffer *vb,
                  unsigned int plane_no)
 {
     if (plane_no < vb->num_planes)
         return vb->planes[plane_no].bytesused;
     return 0;
 }
 
 /**
  * vb2_plane_size() - return plane size in bytes.
  * @vb:     pointer to &struct vb2_buffer to which the plane in
  *      question belongs to.
  * @plane_no:   plane number for which size should be returned.
  */
 static inline unsigned long
 vb2_plane_size(struct vb2_buffer *vb, unsigned int plane_no)
 {
     if (plane_no < vb->num_planes)
         return vb->planes[plane_no].length;
     return 0;
 }
 
 /**
  * vb2_start_streaming_called() - return streaming status of driver.
  * @q:      pointer to &struct vb2_queue with videobuf2 queue.
  */
 static inline bool vb2_start_streaming_called(struct vb2_queue *q)
 {
     return q->start_streaming_called;
 }
 
 /**
  * vb2_clear_last_buffer_dequeued() - clear last buffer dequeued flag of queue.
  * @q:      pointer to &struct vb2_queue with videobuf2 queue.
  */
 static inline void vb2_clear_last_buffer_dequeued(struct vb2_queue *q)
 {
     q->last_buffer_dequeued = false;
 }
 
 /**
  * vb2_get_buffer() - get a buffer from a queue
  * @q:      pointer to &struct vb2_queue with videobuf2 queue.
  * @index:  buffer index
  *
  * This function obtains a buffer from a queue, by its index.
  * Keep in mind that there is no refcounting involved in this
  * operation, so the buffer lifetime should be taken into
  * consideration.
  */
 static inline struct vb2_buffer *vb2_get_buffer(struct vb2_queue *q,
                         unsigned int index)
 {
     if (index < q->num_buffers)
         return q->bufs[index];
     return NULL;
 }
 
 /*
  * 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 VIDIOC_REQBUFS(0)) call.
  *
  * @vb:     buffer for which plane size should be returned.
  * @q:      pointer to &struct vb2_queue with videobuf2 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.
  *
  * @q:      pointer to &struct vb2_queue with videobuf2 queue.
  * @memory: memory model, as defined by enum &vb2_memory.
  * @type:   private buffer type whose content is defined by the vb2-core
  *      caller. For example, for V4L2, it should match
  *      the types defined on enum &v4l2_buf_type.
  */
 int vb2_verify_memory_type(struct vb2_queue *q,
         enum vb2_memory memory, unsigned int type);
 
 /**
  * vb2_request_object_is_buffer() - return true if the object is a buffer
  *
  * @obj:    the request object.
  */
 bool vb2_request_object_is_buffer(struct media_request_object *obj);
 
 /**
  * vb2_request_buffer_cnt() - return the number of buffers in the request
  *
  * @req:    the request.
  */
 unsigned int vb2_request_buffer_cnt(struct media_request *req);
 
 #endif /* _MEDIA_VIDEOBUF2_CORE_H */

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