Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

[linux-2.6-microblaze.git] / include / media / videobuf2-core.h

/*
 * 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>

#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_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. Additional gfp_flags to use when allocating the
 *              are also passed to this operation. These flags are from the
 *              gfp_flags field of vb2_queue. 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 device *dev, unsigned long attrs,
                                  unsigned long size,
                                  enum dma_data_direction dma_dir,
                                  gfp_t gfp_flags);
        void            (*put)(void *buf_priv);
        struct dma_buf *(*get_dmabuf)(void *buf_priv, unsigned long flags);

        void            *(*get_userptr)(struct device *dev, unsigned long vaddr,
                                        unsigned long size,
                                        enum dma_data_direction dma_dir);
        void            (*put_userptr)(void *buf_priv);

        void            (*prepare)(void *buf_priv);
        void            (*finish)(void *buf_priv);

        void            *(*attach_dmabuf)(struct device *dev,
                                          struct dma_buf *dbuf,
                                          unsigned long size,
                                          enum dma_data_direction dma_dir);
        void            (*detach_dmabuf)(void *buf_priv);
        int             (*map_dmabuf)(void *buf_priv);
        void            (*unmap_dmabuf)(void *buf_priv);

        void            *(*vaddr)(void *buf_priv);
        void            *(*cookie)(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.
 * @min_length: minimum required size of this plane (NOT the payload) in bytes.
 *              @length is always greater or equal to @min_length.
 * @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.
         * 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;

        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.
 * @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
 */
struct vb2_queue {
        unsigned int                    type;
        unsigned int                    io_modes;
        struct device                   *dev;
        unsigned long                   dma_attrs;
        unsigned                        bidirectional:1;
        unsigned                        fileio_read_once:1;
        unsigned                        fileio_write_immediately:1;
        unsigned                        allow_zero_bytesused:1;
        unsigned                   quirk_poll_must_check_waiting_for_buffers:1;
        unsigned                        supports_requests:1;
        unsigned                        requires_requests:1;
        unsigned                        uses_qbuf:1;
        unsigned                        uses_requests: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;

#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_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.
 * @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 *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.
 * @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 *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_read() - 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)
{
        if (plane_no < vb->num_planes)
                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 */