// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Memory-to-memory device framework for Video for Linux 2 and videobuf.
 *
 * Helper functions for devices that use videobuf buffers for both their
 * source and destination.
 *
 * Copyright (c) 2009-2010 Samsung Electronics Co., Ltd.
 * Pawel Osciak, <pawel@osciak.com>
 * Marek Szyprowski, <m.szyprowski@samsung.com>
 */
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/slab.h>

#include <media/media-device.h>
#include <media/videobuf2-v4l2.h>
#include <media/v4l2-mem2mem.h>
#include <media/v4l2-dev.h>
#include <media/v4l2-device.h>
#include <media/v4l2-fh.h>
#include <media/v4l2-event.h>

MODULE_DESCRIPTION("Mem to mem device framework for videobuf");
MODULE_AUTHOR("Pawel Osciak, <pawel@osciak.com>");
MODULE_LICENSE("GPL");

static bool debug;
module_param(debug, bool, 0644);

#define dprintk(fmt, arg...)                                            \
        do {                                                            \
                if (debug)                                              \
                        printk(KERN_DEBUG "%s: " fmt, __func__, ## arg);\
        } while (0)


/* Instance is already queued on the job_queue */
#define TRANS_QUEUED            (1 << 0)
/* Instance is currently running in hardware */
#define TRANS_RUNNING           (1 << 1)
/* Instance is currently aborting */
#define TRANS_ABORT             (1 << 2)


/* The job queue is not running new jobs */
#define QUEUE_PAUSED            (1 << 0)


/* Offset base for buffers on the destination queue - used to distinguish
 * between source and destination buffers when mmapping - they receive the same
 * offsets but for different queues */
#define DST_QUEUE_OFF_BASE      (1 << 30)

enum v4l2_m2m_entity_type {
        MEM2MEM_ENT_TYPE_SOURCE,
        MEM2MEM_ENT_TYPE_SINK,
        MEM2MEM_ENT_TYPE_PROC
};

static const char * const m2m_entity_name[] = {
        "source",
        "sink",
        "proc"
};

/**
 * struct v4l2_m2m_dev - per-device context
 * @source:             &struct media_entity pointer with the source entity
 *                      Used only when the M2M device is registered via
 *                      v4l2_m2m_unregister_media_controller().
 * @source_pad:         &struct media_pad with the source pad.
 *                      Used only when the M2M device is registered via
 *                      v4l2_m2m_unregister_media_controller().
 * @sink:               &struct media_entity pointer with the sink entity
 *                      Used only when the M2M device is registered via
 *                      v4l2_m2m_unregister_media_controller().
 * @sink_pad:           &struct media_pad with the sink pad.
 *                      Used only when the M2M device is registered via
 *                      v4l2_m2m_unregister_media_controller().
 * @proc:               &struct media_entity pointer with the M2M device itself.
 * @proc_pads:          &struct media_pad with the @proc pads.
 *                      Used only when the M2M device is registered via
 *                      v4l2_m2m_unregister_media_controller().
 * @intf_devnode:       &struct media_intf devnode pointer with the interface
 *                      with controls the M2M device.
 * @curr_ctx:           currently running instance
 * @job_queue:          instances queued to run
 * @job_spinlock:       protects job_queue
 * @job_work:           worker to run queued jobs.
 * @job_queue_flags:    flags of the queue status, %QUEUE_PAUSED.
 * @m2m_ops:            driver callbacks
 */
struct v4l2_m2m_dev {
        struct v4l2_m2m_ctx     *curr_ctx;
#ifdef CONFIG_MEDIA_CONTROLLER
        struct media_entity     *source;
        struct media_pad        source_pad;
        struct media_entity     sink;
        struct media_pad        sink_pad;
        struct media_entity     proc;
        struct media_pad        proc_pads[2];
        struct media_intf_devnode *intf_devnode;
#endif

        struct list_head        job_queue;
        spinlock_t              job_spinlock;
        struct work_struct      job_work;
        unsigned long           job_queue_flags;

        const struct v4l2_m2m_ops *m2m_ops;
};

static struct v4l2_m2m_queue_ctx *get_queue_ctx(struct v4l2_m2m_ctx *m2m_ctx,
                                                enum v4l2_buf_type type)
{
        if (V4L2_TYPE_IS_OUTPUT(type))
                return &m2m_ctx->out_q_ctx;
        else
                return &m2m_ctx->cap_q_ctx;
}

struct vb2_queue *v4l2_m2m_get_vq(struct v4l2_m2m_ctx *m2m_ctx,
                                       enum v4l2_buf_type type)
{
        struct v4l2_m2m_queue_ctx *q_ctx;

        q_ctx = get_queue_ctx(m2m_ctx, type);
        if (!q_ctx)
                return NULL;

        return &q_ctx->q;
}
EXPORT_SYMBOL(v4l2_m2m_get_vq);

struct vb2_v4l2_buffer *v4l2_m2m_next_buf(struct v4l2_m2m_queue_ctx *q_ctx)
{
        struct v4l2_m2m_buffer *b;
        unsigned long flags;

        spin_lock_irqsave(&q_ctx->rdy_spinlock, flags);

        if (list_empty(&q_ctx->rdy_queue)) {
                spin_unlock_irqrestore(&q_ctx->rdy_spinlock, flags);
                return NULL;
        }

        b = list_first_entry(&q_ctx->rdy_queue, struct v4l2_m2m_buffer, list);
        spin_unlock_irqrestore(&q_ctx->rdy_spinlock, flags);
        return &b->vb;
}
EXPORT_SYMBOL_GPL(v4l2_m2m_next_buf);

struct vb2_v4l2_buffer *v4l2_m2m_last_buf(struct v4l2_m2m_queue_ctx *q_ctx)
{
        struct v4l2_m2m_buffer *b;
        unsigned long flags;

        spin_lock_irqsave(&q_ctx->rdy_spinlock, flags);

        if (list_empty(&q_ctx->rdy_queue)) {
                spin_unlock_irqrestore(&q_ctx->rdy_spinlock, flags);
                return NULL;
        }

        b = list_last_entry(&q_ctx->rdy_queue, struct v4l2_m2m_buffer, list);
        spin_unlock_irqrestore(&q_ctx->rdy_spinlock, flags);
        return &b->vb;
}
EXPORT_SYMBOL_GPL(v4l2_m2m_last_buf);

struct vb2_v4l2_buffer *v4l2_m2m_buf_remove(struct v4l2_m2m_queue_ctx *q_ctx)
{
        struct v4l2_m2m_buffer *b;
        unsigned long flags;

        spin_lock_irqsave(&q_ctx->rdy_spinlock, flags);
        if (list_empty(&q_ctx->rdy_queue)) {
                spin_unlock_irqrestore(&q_ctx->rdy_spinlock, flags);
                return NULL;
        }
        b = list_first_entry(&q_ctx->rdy_queue, struct v4l2_m2m_buffer, list);
        list_del(&b->list);
        q_ctx->num_rdy--;
        spin_unlock_irqrestore(&q_ctx->rdy_spinlock, flags);

        return &b->vb;
}
EXPORT_SYMBOL_GPL(v4l2_m2m_buf_remove);

void v4l2_m2m_buf_remove_by_buf(struct v4l2_m2m_queue_ctx *q_ctx,
                                struct vb2_v4l2_buffer *vbuf)
{
        struct v4l2_m2m_buffer *b;
        unsigned long flags;

        spin_lock_irqsave(&q_ctx->rdy_spinlock, flags);
        b = container_of(vbuf, struct v4l2_m2m_buffer, vb);
        list_del(&b->list);
        q_ctx->num_rdy--;
        spin_unlock_irqrestore(&q_ctx->rdy_spinlock, flags);
}
EXPORT_SYMBOL_GPL(v4l2_m2m_buf_remove_by_buf);

struct vb2_v4l2_buffer *
v4l2_m2m_buf_remove_by_idx(struct v4l2_m2m_queue_ctx *q_ctx, unsigned int idx)

{
        struct v4l2_m2m_buffer *b, *tmp;
        struct vb2_v4l2_buffer *ret = NULL;
        unsigned long flags;

        spin_lock_irqsave(&q_ctx->rdy_spinlock, flags);
        list_for_each_entry_safe(b, tmp, &q_ctx->rdy_queue, list) {
                if (b->vb.vb2_buf.index == idx) {
                        list_del(&b->list);
                        q_ctx->num_rdy--;
                        ret = &b->vb;
                        break;
                }
        }
        spin_unlock_irqrestore(&q_ctx->rdy_spinlock, flags);

        return ret;
}
EXPORT_SYMBOL_GPL(v4l2_m2m_buf_remove_by_idx);

/*
 * Scheduling handlers
 */

void *v4l2_m2m_get_curr_priv(struct v4l2_m2m_dev *m2m_dev)
{
        unsigned long flags;
        void *ret = NULL;

        spin_lock_irqsave(&m2m_dev->job_spinlock, flags);
        if (m2m_dev->curr_ctx)
                ret = m2m_dev->curr_ctx->priv;
        spin_unlock_irqrestore(&m2m_dev->job_spinlock, flags);

        return ret;
}
EXPORT_SYMBOL(v4l2_m2m_get_curr_priv);

/**
 * v4l2_m2m_try_run() - select next job to perform and run it if possible
 * @m2m_dev: per-device context
 *
 * Get next transaction (if present) from the waiting jobs list and run it.
 *
 * Note that this function can run on a given v4l2_m2m_ctx context,
 * but call .device_run for another context.
 */
static void v4l2_m2m_try_run(struct v4l2_m2m_dev *m2m_dev)
{
        unsigned long flags;

        spin_lock_irqsave(&m2m_dev->job_spinlock, flags);
        if (NULL != m2m_dev->curr_ctx) {
                spin_unlock_irqrestore(&m2m_dev->job_spinlock, flags);
                dprintk("Another instance is running, won't run now\n");
                return;
        }

        if (list_empty(&m2m_dev->job_queue)) {
                spin_unlock_irqrestore(&m2m_dev->job_spinlock, flags);
                dprintk("No job pending\n");
                return;
        }

        if (m2m_dev->job_queue_flags & QUEUE_PAUSED) {
                spin_unlock_irqrestore(&m2m_dev->job_spinlock, flags);
                dprintk("Running new jobs is paused\n");
                return;
        }

        m2m_dev->curr_ctx = list_first_entry(&m2m_dev->job_queue,
                                   struct v4l2_m2m_ctx, queue);
        m2m_dev->curr_ctx->job_flags |= TRANS_RUNNING;
        spin_unlock_irqrestore(&m2m_dev->job_spinlock, flags);

        dprintk("Running job on m2m_ctx: %p\n", m2m_dev->curr_ctx);
        m2m_dev->m2m_ops->device_run(m2m_dev->curr_ctx->priv);
}

/*
 * __v4l2_m2m_try_queue() - queue a job
 * @m2m_dev: m2m device
 * @m2m_ctx: m2m context
 *
 * Check if this context is ready to queue a job.
 *
 * This function can run in interrupt context.
 */
static void __v4l2_m2m_try_queue(struct v4l2_m2m_dev *m2m_dev,
                                 struct v4l2_m2m_ctx *m2m_ctx)
{
        unsigned long flags_job;
        struct vb2_v4l2_buffer *dst, *src;

        dprintk("Trying to schedule a job for m2m_ctx: %p\n", m2m_ctx);

        if (!m2m_ctx->out_q_ctx.q.streaming
            || !m2m_ctx->cap_q_ctx.q.streaming) {
                dprintk("Streaming needs to be on for both queues\n");
                return;
        }

        spin_lock_irqsave(&m2m_dev->job_spinlock, flags_job);

        /* If the context is aborted then don't schedule it */
        if (m2m_ctx->job_flags & TRANS_ABORT) {
                dprintk("Aborted context\n");
                goto job_unlock;
        }

        if (m2m_ctx->job_flags & TRANS_QUEUED) {
                dprintk("On job queue already\n");
                goto job_unlock;
        }

        src = v4l2_m2m_next_src_buf(m2m_ctx);
        dst = v4l2_m2m_next_dst_buf(m2m_ctx);
        if (!src && !m2m_ctx->out_q_ctx.buffered) {
                dprintk("No input buffers available\n");
                goto job_unlock;
        }
        if (!dst && !m2m_ctx->cap_q_ctx.buffered) {
                dprintk("No output buffers available\n");
                goto job_unlock;
        }

        m2m_ctx->new_frame = true;

        if (src && dst && dst->is_held &&
            dst->vb2_buf.copied_timestamp &&
            dst->vb2_buf.timestamp != src->vb2_buf.timestamp) {
                dst->is_held = false;
                v4l2_m2m_dst_buf_remove(m2m_ctx);
                v4l2_m2m_buf_done(dst, VB2_BUF_STATE_DONE);
                dst = v4l2_m2m_next_dst_buf(m2m_ctx);

                if (!dst && !m2m_ctx->cap_q_ctx.buffered) {
                        dprintk("No output buffers available after returning held buffer\n");
                        goto job_unlock;
                }
        }

        if (src && dst && (m2m_ctx->out_q_ctx.q.subsystem_flags &
                           VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF))
                m2m_ctx->new_frame = !dst->vb2_buf.copied_timestamp ||
                        dst->vb2_buf.timestamp != src->vb2_buf.timestamp;

        if (m2m_ctx->has_stopped) {
                dprintk("Device has stopped\n");
                goto job_unlock;
        }

        if (m2m_dev->m2m_ops->job_ready
                && (!m2m_dev->m2m_ops->job_ready(m2m_ctx->priv))) {
                dprintk("Driver not ready\n");
                goto job_unlock;
        }

        list_add_tail(&m2m_ctx->queue, &m2m_dev->job_queue);
        m2m_ctx->job_flags |= TRANS_QUEUED;

job_unlock:
        spin_unlock_irqrestore(&m2m_dev->job_spinlock, flags_job);
}

/**
 * v4l2_m2m_try_schedule() - schedule and possibly run a job for any context
 * @m2m_ctx: m2m context
 *
 * Check if this context is ready to queue a job. If suitable,
 * run the next queued job on the mem2mem device.
 *
 * This function shouldn't run in interrupt context.
 *
 * Note that v4l2_m2m_try_schedule() can schedule one job for this context,
 * and then run another job for another context.
 */
void v4l2_m2m_try_schedule(struct v4l2_m2m_ctx *m2m_ctx)
{
        struct v4l2_m2m_dev *m2m_dev = m2m_ctx->m2m_dev;

        __v4l2_m2m_try_queue(m2m_dev, m2m_ctx);
        v4l2_m2m_try_run(m2m_dev);
}
EXPORT_SYMBOL_GPL(v4l2_m2m_try_schedule);

/**
 * v4l2_m2m_device_run_work() - run pending jobs for the context
 * @work: Work structure used for scheduling the execution of this function.
 */
static void v4l2_m2m_device_run_work(struct work_struct *work)
{
        struct v4l2_m2m_dev *m2m_dev =
                container_of(work, struct v4l2_m2m_dev, job_work);

        v4l2_m2m_try_run(m2m_dev);
}

/**
 * v4l2_m2m_cancel_job() - cancel pending jobs for the context
 * @m2m_ctx: m2m context with jobs to be canceled
 *
 * In case of streamoff or release called on any context,
 * 1] If the context is currently running, then abort job will be called
 * 2] If the context is queued, then the context will be removed from
 *    the job_queue
 */
static void v4l2_m2m_cancel_job(struct v4l2_m2m_ctx *m2m_ctx)
{
        struct v4l2_m2m_dev *m2m_dev;
        unsigned long flags;

        m2m_dev = m2m_ctx->m2m_dev;
        spin_lock_irqsave(&m2m_dev->job_spinlock, flags);

        m2m_ctx->job_flags |= TRANS_ABORT;
        if (m2m_ctx->job_flags & TRANS_RUNNING) {
                spin_unlock_irqrestore(&m2m_dev->job_spinlock, flags);
                if (m2m_dev->m2m_ops->job_abort)
                        m2m_dev->m2m_ops->job_abort(m2m_ctx->priv);
                dprintk("m2m_ctx %p running, will wait to complete\n", m2m_ctx);
                wait_event(m2m_ctx->finished,
                                !(m2m_ctx->job_flags & TRANS_RUNNING));
        } else if (m2m_ctx->job_flags & TRANS_QUEUED) {
                list_del(&m2m_ctx->queue);
                m2m_ctx->job_flags &= ~(TRANS_QUEUED | TRANS_RUNNING);
                spin_unlock_irqrestore(&m2m_dev->job_spinlock, flags);
                dprintk("m2m_ctx: %p had been on queue and was removed\n",
                        m2m_ctx);
        } else {
                /* Do nothing, was not on queue/running */
                spin_unlock_irqrestore(&m2m_dev->job_spinlock, flags);
        }
}

/*
 * Schedule the next job, called from v4l2_m2m_job_finish() or
 * v4l2_m2m_buf_done_and_job_finish().
 */
static void v4l2_m2m_schedule_next_job(struct v4l2_m2m_dev *m2m_dev,
                                       struct v4l2_m2m_ctx *m2m_ctx)
{
        /*
         * This instance might have more buffers ready, but since we do not
         * allow more than one job on the job_queue per instance, each has
         * to be scheduled separately after the previous one finishes.
         */
        __v4l2_m2m_try_queue(m2m_dev, m2m_ctx);

        /*
         * We might be running in atomic context,
         * but the job must be run in non-atomic context.
         */
        schedule_work(&m2m_dev->job_work);
}

/*
 * Assumes job_spinlock is held, called from v4l2_m2m_job_finish() or
 * v4l2_m2m_buf_done_and_job_finish().
 */
static bool _v4l2_m2m_job_finish(struct v4l2_m2m_dev *m2m_dev,
                                 struct v4l2_m2m_ctx *m2m_ctx)
{
        if (!m2m_dev->curr_ctx || m2m_dev->curr_ctx != m2m_ctx) {
                dprintk("Called by an instance not currently running\n");
                return false;
        }

        list_del(&m2m_dev->curr_ctx->queue);
        m2m_dev->curr_ctx->job_flags &= ~(TRANS_QUEUED | TRANS_RUNNING);
        wake_up(&m2m_dev->curr_ctx->finished);
        m2m_dev->curr_ctx = NULL;
        return true;
}

void v4l2_m2m_job_finish(struct v4l2_m2m_dev *m2m_dev,
                         struct v4l2_m2m_ctx *m2m_ctx)
{
        unsigned long flags;
        bool schedule_next;

        /*
         * This function should not be used for drivers that support
         * holding capture buffers. Those should use
         * v4l2_m2m_buf_done_and_job_finish() instead.
         */
        WARN_ON(m2m_ctx->out_q_ctx.q.subsystem_flags &
                VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF);
        spin_lock_irqsave(&m2m_dev->job_spinlock, flags);
        schedule_next = _v4l2_m2m_job_finish(m2m_dev, m2m_ctx);
        spin_unlock_irqrestore(&m2m_dev->job_spinlock, flags);

        if (schedule_next)
                v4l2_m2m_schedule_next_job(m2m_dev, m2m_ctx);
}
EXPORT_SYMBOL(v4l2_m2m_job_finish);

void v4l2_m2m_buf_done_and_job_finish(struct v4l2_m2m_dev *m2m_dev,
                                      struct v4l2_m2m_ctx *m2m_ctx,
                                      enum vb2_buffer_state state)
{
        struct vb2_v4l2_buffer *src_buf, *dst_buf;
        bool schedule_next = false;
        unsigned long flags;

        spin_lock_irqsave(&m2m_dev->job_spinlock, flags);
        src_buf = v4l2_m2m_src_buf_remove(m2m_ctx);
        dst_buf = v4l2_m2m_next_dst_buf(m2m_ctx);

        if (WARN_ON(!src_buf || !dst_buf))
                goto unlock;
        dst_buf->is_held = src_buf->flags & V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF;
        if (!dst_buf->is_held) {
                v4l2_m2m_dst_buf_remove(m2m_ctx);
                v4l2_m2m_buf_done(dst_buf, state);
        }
        /*
         * If the request API is being used, returning the OUTPUT
         * (src) buffer will wake-up any process waiting on the
         * request file descriptor.
         *
         * Therefore, return the CAPTURE (dst) buffer first,
         * to avoid signalling the request file descriptor
         * before the CAPTURE buffer is done.
         */
        v4l2_m2m_buf_done(src_buf, state);
        schedule_next = _v4l2_m2m_job_finish(m2m_dev, m2m_ctx);
unlock:
        spin_unlock_irqrestore(&m2m_dev->job_spinlock, flags);

        if (schedule_next)
                v4l2_m2m_schedule_next_job(m2m_dev, m2m_ctx);
}
EXPORT_SYMBOL(v4l2_m2m_buf_done_and_job_finish);

void v4l2_m2m_suspend(struct v4l2_m2m_dev *m2m_dev)
{
        unsigned long flags;
        struct v4l2_m2m_ctx *curr_ctx;

        spin_lock_irqsave(&m2m_dev->job_spinlock, flags);
        m2m_dev->job_queue_flags |= QUEUE_PAUSED;
        curr_ctx = m2m_dev->curr_ctx;
        spin_unlock_irqrestore(&m2m_dev->job_spinlock, flags);

        if (curr_ctx)
                wait_event(curr_ctx->finished,
                           !(curr_ctx->job_flags & TRANS_RUNNING));
}
EXPORT_SYMBOL(v4l2_m2m_suspend);

void v4l2_m2m_resume(struct v4l2_m2m_dev *m2m_dev)
{
        unsigned long flags;

        spin_lock_irqsave(&m2m_dev->job_spinlock, flags);
        m2m_dev->job_queue_flags &= ~QUEUE_PAUSED;
        spin_unlock_irqrestore(&m2m_dev->job_spinlock, flags);

        v4l2_m2m_try_run(m2m_dev);
}
EXPORT_SYMBOL(v4l2_m2m_resume);

int v4l2_m2m_reqbufs(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
                     struct v4l2_requestbuffers *reqbufs)
{
        struct vb2_queue *vq;
        int ret;

        vq = v4l2_m2m_get_vq(m2m_ctx, reqbufs->type);
        ret = vb2_reqbufs(vq, reqbufs);
        /* If count == 0, then the owner has released all buffers and he
           is no longer owner of the queue. Otherwise we have an owner. */
        if (ret == 0)
                vq->owner = reqbufs->count ? file->private_data : NULL;

        return ret;
}
EXPORT_SYMBOL_GPL(v4l2_m2m_reqbufs);

int v4l2_m2m_querybuf(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
                      struct v4l2_buffer *buf)
{
        struct vb2_queue *vq;
        int ret = 0;
        unsigned int i;

        vq = v4l2_m2m_get_vq(m2m_ctx, buf->type);
        ret = vb2_querybuf(vq, buf);

        /* Adjust MMAP memory offsets for the CAPTURE queue */
        if (buf->memory == V4L2_MEMORY_MMAP && V4L2_TYPE_IS_CAPTURE(vq->type)) {
                if (V4L2_TYPE_IS_MULTIPLANAR(vq->type)) {
                        for (i = 0; i < buf->length; ++i)
                                buf->m.planes[i].m.mem_offset
                                        += DST_QUEUE_OFF_BASE;
                } else {
                        buf->m.offset += DST_QUEUE_OFF_BASE;
                }
        }

        return ret;
}
EXPORT_SYMBOL_GPL(v4l2_m2m_querybuf);

/*
 * This will add the LAST flag and mark the buffer management
 * state as stopped.
 * This is called when the last capture buffer must be flagged as LAST
 * in draining mode from the encoder/decoder driver buf_queue() callback
 * or from v4l2_update_last_buf_state() when a capture buffer is available.
 */
void v4l2_m2m_last_buffer_done(struct v4l2_m2m_ctx *m2m_ctx,
                               struct vb2_v4l2_buffer *vbuf)
{
        vbuf->flags |= V4L2_BUF_FLAG_LAST;
        vb2_buffer_done(&vbuf->vb2_buf, VB2_BUF_STATE_DONE);

        v4l2_m2m_mark_stopped(m2m_ctx);
}
EXPORT_SYMBOL_GPL(v4l2_m2m_last_buffer_done);

/* When stop command is issued, update buffer management state */
static int v4l2_update_last_buf_state(struct v4l2_m2m_ctx *m2m_ctx)
{
        struct vb2_v4l2_buffer *next_dst_buf;

        if (m2m_ctx->is_draining)
                return -EBUSY;

        if (m2m_ctx->has_stopped)
                return 0;

        m2m_ctx->last_src_buf = v4l2_m2m_last_src_buf(m2m_ctx);
        m2m_ctx->is_draining = true;

        /*
         * The processing of the last output buffer queued before
         * the STOP command is expected to mark the buffer management
         * state as stopped with v4l2_m2m_mark_stopped().
         */
        if (m2m_ctx->last_src_buf)
                return 0;

        /*
         * In case the output queue is empty, try to mark the last capture
         * buffer as LAST.
         */
        next_dst_buf = v4l2_m2m_dst_buf_remove(m2m_ctx);
        if (!next_dst_buf) {
                /*
                 * Wait for the next queued one in encoder/decoder driver
                 * buf_queue() callback using the v4l2_m2m_dst_buf_is_last()
                 * helper or in v4l2_m2m_qbuf() if encoder/decoder is not yet
                 * streaming.
                 */
                m2m_ctx->next_buf_last = true;
                return 0;
        }

        v4l2_m2m_last_buffer_done(m2m_ctx, next_dst_buf);

        return 0;
}

/*
 * Updates the encoding/decoding buffer management state, should
 * be called from encoder/decoder drivers start_streaming()
 */
void v4l2_m2m_update_start_streaming_state(struct v4l2_m2m_ctx *m2m_ctx,
                                           struct vb2_queue *q)
{
        /* If start streaming again, untag the last output buffer */
        if (V4L2_TYPE_IS_OUTPUT(q->type))
                m2m_ctx->last_src_buf = NULL;
}
EXPORT_SYMBOL_GPL(v4l2_m2m_update_start_streaming_state);

/*
 * Updates the encoding/decoding buffer management state, should
 * be called from encoder/decoder driver stop_streaming()
 */
void v4l2_m2m_update_stop_streaming_state(struct v4l2_m2m_ctx *m2m_ctx,
                                          struct vb2_queue *q)
{
        if (V4L2_TYPE_IS_OUTPUT(q->type)) {
                /*
                 * If in draining state, either mark next dst buffer as
                 * done or flag next one to be marked as done either
                 * in encoder/decoder driver buf_queue() callback using
                 * the v4l2_m2m_dst_buf_is_last() helper or in v4l2_m2m_qbuf()
                 * if encoder/decoder is not yet streaming
                 */
                if (m2m_ctx->is_draining) {
                        struct vb2_v4l2_buffer *next_dst_buf;

                        m2m_ctx->last_src_buf = NULL;
                        next_dst_buf = v4l2_m2m_dst_buf_remove(m2m_ctx);
                        if (!next_dst_buf)
                                m2m_ctx->next_buf_last = true;
                        else
                                v4l2_m2m_last_buffer_done(m2m_ctx,
                                                          next_dst_buf);
                }
        } else {
                v4l2_m2m_clear_state(m2m_ctx);
        }
}
EXPORT_SYMBOL_GPL(v4l2_m2m_update_stop_streaming_state);

static void v4l2_m2m_force_last_buf_done(struct v4l2_m2m_ctx *m2m_ctx,
                                         struct vb2_queue *q)
{
        struct vb2_buffer *vb;
        struct vb2_v4l2_buffer *vbuf;
        unsigned int i;

        if (WARN_ON(q->is_output))
                return;
        if (list_empty(&q->queued_list))
                return;

        vb = list_first_entry(&q->queued_list, struct vb2_buffer, queued_entry);
        for (i = 0; i < vb->num_planes; i++)
                vb2_set_plane_payload(vb, i, 0);

        /*
         * Since the buffer hasn't been queued to the ready queue,
         * mark is active and owned before marking it LAST and DONE
         */
        vb->state = VB2_BUF_STATE_ACTIVE;
        atomic_inc(&q->owned_by_drv_count);

        vbuf = to_vb2_v4l2_buffer(vb);
        vbuf->field = V4L2_FIELD_NONE;

        v4l2_m2m_last_buffer_done(m2m_ctx, vbuf);
}

int v4l2_m2m_qbuf(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
                  struct v4l2_buffer *buf)
{
        struct video_device *vdev = video_devdata(file);
        struct vb2_queue *vq;
        int ret;

        vq = v4l2_m2m_get_vq(m2m_ctx, buf->type);
        if (V4L2_TYPE_IS_CAPTURE(vq->type) &&
            (buf->flags & V4L2_BUF_FLAG_REQUEST_FD)) {
                dprintk("%s: requests cannot be used with capture buffers\n",
                        __func__);
                return -EPERM;
        }

        ret = vb2_qbuf(vq, vdev->v4l2_dev->mdev, buf);
        if (ret)
                return ret;

        /*
         * If the capture queue is streaming, but streaming hasn't started
         * on the device, but was asked to stop, mark the previously queued
         * buffer as DONE with LAST flag since it won't be queued on the
         * device.
         */
        if (V4L2_TYPE_IS_CAPTURE(vq->type) &&
            vb2_is_streaming(vq) && !vb2_start_streaming_called(vq) &&
           (v4l2_m2m_has_stopped(m2m_ctx) || v4l2_m2m_dst_buf_is_last(m2m_ctx)))
                v4l2_m2m_force_last_buf_done(m2m_ctx, vq);
        else if (!(buf->flags & V4L2_BUF_FLAG_IN_REQUEST))
                v4l2_m2m_try_schedule(m2m_ctx);

        return 0;
}
EXPORT_SYMBOL_GPL(v4l2_m2m_qbuf);

int v4l2_m2m_dqbuf(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
                   struct v4l2_buffer *buf)
{
        struct vb2_queue *vq;

        vq = v4l2_m2m_get_vq(m2m_ctx, buf->type);
        return vb2_dqbuf(vq, buf, file->f_flags & O_NONBLOCK);
}
EXPORT_SYMBOL_GPL(v4l2_m2m_dqbuf);

int v4l2_m2m_prepare_buf(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
                         struct v4l2_buffer *buf)
{
        struct video_device *vdev = video_devdata(file);
        struct vb2_queue *vq;

        vq = v4l2_m2m_get_vq(m2m_ctx, buf->type);
        return vb2_prepare_buf(vq, vdev->v4l2_dev->mdev, buf);
}
EXPORT_SYMBOL_GPL(v4l2_m2m_prepare_buf);

int v4l2_m2m_create_bufs(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
                         struct v4l2_create_buffers *create)
{
        struct vb2_queue *vq;

        vq = v4l2_m2m_get_vq(m2m_ctx, create->format.type);
        return vb2_create_bufs(vq, create);
}
EXPORT_SYMBOL_GPL(v4l2_m2m_create_bufs);

int v4l2_m2m_expbuf(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
                  struct v4l2_exportbuffer *eb)
{
        struct vb2_queue *vq;

        vq = v4l2_m2m_get_vq(m2m_ctx, eb->type);
        return vb2_expbuf(vq, eb);
}
EXPORT_SYMBOL_GPL(v4l2_m2m_expbuf);

int v4l2_m2m_streamon(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
                      enum v4l2_buf_type type)
{
        struct vb2_queue *vq;
        int ret;

        vq = v4l2_m2m_get_vq(m2m_ctx, type);
        ret = vb2_streamon(vq, type);
        if (!ret)
                v4l2_m2m_try_schedule(m2m_ctx);

        return ret;
}
EXPORT_SYMBOL_GPL(v4l2_m2m_streamon);

int v4l2_m2m_streamoff(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
                       enum v4l2_buf_type type)
{
        struct v4l2_m2m_dev *m2m_dev;
        struct v4l2_m2m_queue_ctx *q_ctx;
        unsigned long flags_job, flags;
        int ret;

        /* wait until the current context is dequeued from job_queue */
        v4l2_m2m_cancel_job(m2m_ctx);

        q_ctx = get_queue_ctx(m2m_ctx, type);
        ret = vb2_streamoff(&q_ctx->q, type);
        if (ret)
                return ret;

        m2m_dev = m2m_ctx->m2m_dev;
        spin_lock_irqsave(&m2m_dev->job_spinlock, flags_job);
        /* We should not be scheduled anymore, since we're dropping a queue. */
        if (m2m_ctx->job_flags & TRANS_QUEUED)
                list_del(&m2m_ctx->queue);
        m2m_ctx->job_flags = 0;

        spin_lock_irqsave(&q_ctx->rdy_spinlock, flags);
        /* Drop queue, since streamoff returns device to the same state as after
         * calling reqbufs. */
        INIT_LIST_HEAD(&q_ctx->rdy_queue);
        q_ctx->num_rdy = 0;
        spin_unlock_irqrestore(&q_ctx->rdy_spinlock, flags);

        if (m2m_dev->curr_ctx == m2m_ctx) {
                m2m_dev->curr_ctx = NULL;
                wake_up(&m2m_ctx->finished);
        }
        spin_unlock_irqrestore(&m2m_dev->job_spinlock, flags_job);

        return 0;
}
EXPORT_SYMBOL_GPL(v4l2_m2m_streamoff);

static __poll_t v4l2_m2m_poll_for_data(struct file *file,
                                       struct v4l2_m2m_ctx *m2m_ctx,
                                       struct poll_table_struct *wait)
{
        struct vb2_queue *src_q, *dst_q;
        __poll_t rc = 0;
        unsigned long flags;

        src_q = v4l2_m2m_get_src_vq(m2m_ctx);
        dst_q = v4l2_m2m_get_dst_vq(m2m_ctx);

        poll_wait(file, &src_q->done_wq, wait);
        poll_wait(file, &dst_q->done_wq, wait);

        /*
         * There has to be at least one buffer queued on each queued_list, which
         * means either in driver already or waiting for driver to claim it
         * and start processing.
         */
        if ((!src_q->streaming || src_q->error ||
             list_empty(&src_q->queued_list)) &&
            (!dst_q->streaming || dst_q->error ||
             list_empty(&dst_q->queued_list)))
                return EPOLLERR;

        spin_lock_irqsave(&src_q->done_lock, flags);
        if (!list_empty(&src_q->done_list))
                rc |= EPOLLOUT | EPOLLWRNORM;
        spin_unlock_irqrestore(&src_q->done_lock, flags);

        spin_lock_irqsave(&dst_q->done_lock, flags);
        /*
         * If the last buffer was dequeued from the capture queue, signal
         * userspace. DQBUF(CAPTURE) will return -EPIPE.
         */
        if (!list_empty(&dst_q->done_list) || dst_q->last_buffer_dequeued)
                rc |= EPOLLIN | EPOLLRDNORM;
        spin_unlock_irqrestore(&dst_q->done_lock, flags);

        return rc;
}

__poll_t v4l2_m2m_poll(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
                       struct poll_table_struct *wait)
{
        struct video_device *vfd = video_devdata(file);
        __poll_t req_events = poll_requested_events(wait);
        __poll_t rc = 0;

        if (req_events & (EPOLLOUT | EPOLLWRNORM | EPOLLIN | EPOLLRDNORM))
                rc = v4l2_m2m_poll_for_data(file, m2m_ctx, wait);

        if (test_bit(V4L2_FL_USES_V4L2_FH, &vfd->flags)) {
                struct v4l2_fh *fh = file->private_data;

                poll_wait(file, &fh->wait, wait);
                if (v4l2_event_pending(fh))
                        rc |= EPOLLPRI;
        }

        return rc;
}
EXPORT_SYMBOL_GPL(v4l2_m2m_poll);

int v4l2_m2m_mmap(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
                         struct vm_area_struct *vma)
{
        unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;
        struct vb2_queue *vq;

        if (offset < DST_QUEUE_OFF_BASE) {
                vq = v4l2_m2m_get_src_vq(m2m_ctx);
        } else {
                vq = v4l2_m2m_get_dst_vq(m2m_ctx);
                vma->vm_pgoff -= (DST_QUEUE_OFF_BASE >> PAGE_SHIFT);
        }

        return vb2_mmap(vq, vma);
}
EXPORT_SYMBOL(v4l2_m2m_mmap);

#if defined(CONFIG_MEDIA_CONTROLLER)
void v4l2_m2m_unregister_media_controller(struct v4l2_m2m_dev *m2m_dev)
{
        media_remove_intf_links(&m2m_dev->intf_devnode->intf);
        media_devnode_remove(m2m_dev->intf_devnode);

        media_entity_remove_links(m2m_dev->source);
        media_entity_remove_links(&m2m_dev->sink);
        media_entity_remove_links(&m2m_dev->proc);
        media_device_unregister_entity(m2m_dev->source);
        media_device_unregister_entity(&m2m_dev->sink);
        media_device_unregister_entity(&m2m_dev->proc);
        kfree(m2m_dev->source->name);
        kfree(m2m_dev->sink.name);
        kfree(m2m_dev->proc.name);
}
EXPORT_SYMBOL_GPL(v4l2_m2m_unregister_media_controller);

static int v4l2_m2m_register_entity(struct media_device *mdev,
        struct v4l2_m2m_dev *m2m_dev, enum v4l2_m2m_entity_type type,
        struct video_device *vdev, int function)
{
        struct media_entity *entity;
        struct media_pad *pads;
        char *name;
        unsigned int len;
        int num_pads;
        int ret;

        switch (type) {
        case MEM2MEM_ENT_TYPE_SOURCE:
                entity = m2m_dev->source;
                pads = &m2m_dev->source_pad;
                pads[0].flags = MEDIA_PAD_FL_SOURCE;
                num_pads = 1;
                break;
        case MEM2MEM_ENT_TYPE_SINK:
                entity = &m2m_dev->sink;
                pads = &m2m_dev->sink_pad;
                pads[0].flags = MEDIA_PAD_FL_SINK;
                num_pads = 1;

                break;
        case MEM2MEM_ENT_TYPE_PROC:
                entity = &m2m_dev->proc;
                pads = m2m_dev->proc_pads;
                pads[0].flags = MEDIA_PAD_FL_SINK;
                pads[1].flags = MEDIA_PAD_FL_SOURCE;
                num_pads = 2;
                break;
        default:
                return -EINVAL;
        }

        entity->obj_type = MEDIA_ENTITY_TYPE_BASE;
        if (type != MEM2MEM_ENT_TYPE_PROC) {
                entity->info.dev.major = VIDEO_MAJOR;
                entity->info.dev.minor = vdev->minor;
        }
        len = strlen(vdev->name) + 2 + strlen(m2m_entity_name[type]);
        name = kmalloc(len, GFP_KERNEL);
        if (!name)
                return -ENOMEM;
        snprintf(name, len, "%s-%s", vdev->name, m2m_entity_name[type]);
        entity->name = name;
        entity->function = function;

        ret = media_entity_pads_init(entity, num_pads, pads);
        if (ret)
                return ret;
        ret = media_device_register_entity(mdev, entity);
        if (ret)
                return ret;

        return 0;
}

int v4l2_m2m_register_media_controller(struct v4l2_m2m_dev *m2m_dev,
                struct video_device *vdev, int function)
{
        struct media_device *mdev = vdev->v4l2_dev->mdev;
        struct media_link *link;
        int ret;

        if (!mdev)
                return 0;

        /* A memory-to-memory device consists in two
         * DMA engine and one video processing entities.
         * The DMA engine entities are linked to a V4L interface
         */

        /* Create the three entities with their pads */
        m2m_dev->source = &vdev->entity;
        ret = v4l2_m2m_register_entity(mdev, m2m_dev,
                        MEM2MEM_ENT_TYPE_SOURCE, vdev, MEDIA_ENT_F_IO_V4L);
        if (ret)
                return ret;
        ret = v4l2_m2m_register_entity(mdev, m2m_dev,
                        MEM2MEM_ENT_TYPE_PROC, vdev, function);
        if (ret)
                goto err_rel_entity0;
        ret = v4l2_m2m_register_entity(mdev, m2m_dev,
                        MEM2MEM_ENT_TYPE_SINK, vdev, MEDIA_ENT_F_IO_V4L);
        if (ret)
                goto err_rel_entity1;

        /* Connect the three entities */
        ret = media_create_pad_link(m2m_dev->source, 0, &m2m_dev->proc, 0,
                        MEDIA_LNK_FL_IMMUTABLE | MEDIA_LNK_FL_ENABLED);
        if (ret)
                goto err_rel_entity2;

        ret = media_create_pad_link(&m2m_dev->proc, 1, &m2m_dev->sink, 0,
                        MEDIA_LNK_FL_IMMUTABLE | MEDIA_LNK_FL_ENABLED);
        if (ret)
                goto err_rm_links0;

        /* Create video interface */
        m2m_dev->intf_devnode = media_devnode_create(mdev,
                        MEDIA_INTF_T_V4L_VIDEO, 0,
                        VIDEO_MAJOR, vdev->minor);
        if (!m2m_dev->intf_devnode) {
                ret = -ENOMEM;
                goto err_rm_links1;
        }

        /* Connect the two DMA engines to the interface */
        link = media_create_intf_link(m2m_dev->source,
                        &m2m_dev->intf_devnode->intf,
                        MEDIA_LNK_FL_IMMUTABLE | MEDIA_LNK_FL_ENABLED);
        if (!link) {
                ret = -ENOMEM;
                goto err_rm_devnode;
        }

        link = media_create_intf_link(&m2m_dev->sink,
                        &m2m_dev->intf_devnode->intf,
                        MEDIA_LNK_FL_IMMUTABLE | MEDIA_LNK_FL_ENABLED);
        if (!link) {
                ret = -ENOMEM;
                goto err_rm_intf_link;
        }
        return 0;

err_rm_intf_link:
        media_remove_intf_links(&m2m_dev->intf_devnode->intf);
err_rm_devnode:
        media_devnode_remove(m2m_dev->intf_devnode);
err_rm_links1:
        media_entity_remove_links(&m2m_dev->sink);
err_rm_links0:
        media_entity_remove_links(&m2m_dev->proc);
        media_entity_remove_links(m2m_dev->source);
err_rel_entity2:
        media_device_unregister_entity(&m2m_dev->proc);
        kfree(m2m_dev->proc.name);
err_rel_entity1:
        media_device_unregister_entity(&m2m_dev->sink);
        kfree(m2m_dev->sink.name);
err_rel_entity0:
        media_device_unregister_entity(m2m_dev->source);
        kfree(m2m_dev->source->name);
        return ret;
        return 0;
}
EXPORT_SYMBOL_GPL(v4l2_m2m_register_media_controller);
#endif

struct v4l2_m2m_dev *v4l2_m2m_init(const struct v4l2_m2m_ops *m2m_ops)
{
        struct v4l2_m2m_dev *m2m_dev;

        if (!m2m_ops || WARN_ON(!m2m_ops->device_run))
                return ERR_PTR(-EINVAL);

        m2m_dev = kzalloc(sizeof *m2m_dev, GFP_KERNEL);
        if (!m2m_dev)
                return ERR_PTR(-ENOMEM);

        m2m_dev->curr_ctx = NULL;
        m2m_dev->m2m_ops = m2m_ops;
        INIT_LIST_HEAD(&m2m_dev->job_queue);
        spin_lock_init(&m2m_dev->job_spinlock);
        INIT_WORK(&m2m_dev->job_work, v4l2_m2m_device_run_work);

        return m2m_dev;
}
EXPORT_SYMBOL_GPL(v4l2_m2m_init);

void v4l2_m2m_release(struct v4l2_m2m_dev *m2m_dev)
{
        kfree(m2m_dev);
}
EXPORT_SYMBOL_GPL(v4l2_m2m_release);

struct v4l2_m2m_ctx *v4l2_m2m_ctx_init(struct v4l2_m2m_dev *m2m_dev,
                void *drv_priv,
                int (*queue_init)(void *priv, struct vb2_queue *src_vq, struct vb2_queue *dst_vq))
{
        struct v4l2_m2m_ctx *m2m_ctx;
        struct v4l2_m2m_queue_ctx *out_q_ctx, *cap_q_ctx;
        int ret;

        m2m_ctx = kzalloc(sizeof *m2m_ctx, GFP_KERNEL);
        if (!m2m_ctx)
                return ERR_PTR(-ENOMEM);

        m2m_ctx->priv = drv_priv;
        m2m_ctx->m2m_dev = m2m_dev;
        init_waitqueue_head(&m2m_ctx->finished);

        out_q_ctx = &m2m_ctx->out_q_ctx;
        cap_q_ctx = &m2m_ctx->cap_q_ctx;

        INIT_LIST_HEAD(&out_q_ctx->rdy_queue);
        INIT_LIST_HEAD(&cap_q_ctx->rdy_queue);
        spin_lock_init(&out_q_ctx->rdy_spinlock);
        spin_lock_init(&cap_q_ctx->rdy_spinlock);

        INIT_LIST_HEAD(&m2m_ctx->queue);

        ret = queue_init(drv_priv, &out_q_ctx->q, &cap_q_ctx->q);

        if (ret)
                goto err;
        /*
         * Both queues should use same the mutex to lock the m2m context.
         * This lock is used in some v4l2_m2m_* helpers.
         */
        if (WARN_ON(out_q_ctx->q.lock != cap_q_ctx->q.lock)) {
                ret = -EINVAL;
                goto err;
        }
        m2m_ctx->q_lock = out_q_ctx->q.lock;

        return m2m_ctx;
err:
        kfree(m2m_ctx);
        return ERR_PTR(ret);
}
EXPORT_SYMBOL_GPL(v4l2_m2m_ctx_init);

void v4l2_m2m_ctx_release(struct v4l2_m2m_ctx *m2m_ctx)
{
        /* wait until the current context is dequeued from job_queue */
        v4l2_m2m_cancel_job(m2m_ctx);

        vb2_queue_release(&m2m_ctx->cap_q_ctx.q);
        vb2_queue_release(&m2m_ctx->out_q_ctx.q);

        kfree(m2m_ctx);
}
EXPORT_SYMBOL_GPL(v4l2_m2m_ctx_release);

void v4l2_m2m_buf_queue(struct v4l2_m2m_ctx *m2m_ctx,
                struct vb2_v4l2_buffer *vbuf)
{
        struct v4l2_m2m_buffer *b = container_of(vbuf,
                                struct v4l2_m2m_buffer, vb);
        struct v4l2_m2m_queue_ctx *q_ctx;
        unsigned long flags;

        q_ctx = get_queue_ctx(m2m_ctx, vbuf->vb2_buf.vb2_queue->type);
        if (!q_ctx)
                return;

        spin_lock_irqsave(&q_ctx->rdy_spinlock, flags);
        list_add_tail(&b->list, &q_ctx->rdy_queue);
        q_ctx->num_rdy++;
        spin_unlock_irqrestore(&q_ctx->rdy_spinlock, flags);
}
EXPORT_SYMBOL_GPL(v4l2_m2m_buf_queue);

void v4l2_m2m_buf_copy_metadata(const struct vb2_v4l2_buffer *out_vb,
                                struct vb2_v4l2_buffer *cap_vb,
                                bool copy_frame_flags)
{
        u32 mask = V4L2_BUF_FLAG_TIMECODE | V4L2_BUF_FLAG_TSTAMP_SRC_MASK;

        if (copy_frame_flags)
                mask |= V4L2_BUF_FLAG_KEYFRAME | V4L2_BUF_FLAG_PFRAME |
                        V4L2_BUF_FLAG_BFRAME;

        cap_vb->vb2_buf.timestamp = out_vb->vb2_buf.timestamp;

        if (out_vb->flags & V4L2_BUF_FLAG_TIMECODE)
                cap_vb->timecode = out_vb->timecode;
        cap_vb->field = out_vb->field;
        cap_vb->flags &= ~mask;
        cap_vb->flags |= out_vb->flags & mask;
        cap_vb->vb2_buf.copied_timestamp = 1;
}
EXPORT_SYMBOL_GPL(v4l2_m2m_buf_copy_metadata);

void v4l2_m2m_request_queue(struct media_request *req)
{
        struct media_request_object *obj, *obj_safe;
        struct v4l2_m2m_ctx *m2m_ctx = NULL;

        /*
         * Queue all objects. Note that buffer objects are at the end of the
         * objects list, after all other object types. Once buffer objects
         * are queued, the driver might delete them immediately (if the driver
         * processes the buffer at once), so we have to use
         * list_for_each_entry_safe() to handle the case where the object we
         * queue is deleted.
         */
        list_for_each_entry_safe(obj, obj_safe, &req->objects, list) {
                struct v4l2_m2m_ctx *m2m_ctx_obj;
                struct vb2_buffer *vb;

                if (!obj->ops->queue)
                        continue;

                if (vb2_request_object_is_buffer(obj)) {
                        /* Sanity checks */
                        vb = container_of(obj, struct vb2_buffer, req_obj);
                        WARN_ON(!V4L2_TYPE_IS_OUTPUT(vb->vb2_queue->type));
                        m2m_ctx_obj = container_of(vb->vb2_queue,
                                                   struct v4l2_m2m_ctx,
                                                   out_q_ctx.q);
                        WARN_ON(m2m_ctx && m2m_ctx_obj != m2m_ctx);
                        m2m_ctx = m2m_ctx_obj;
                }

                /*
                 * The buffer we queue here can in theory be immediately
                 * unbound, hence the use of list_for_each_entry_safe()
                 * above and why we call the queue op last.
                 */
                obj->ops->queue(obj);
        }

        WARN_ON(!m2m_ctx);

        if (m2m_ctx)
                v4l2_m2m_try_schedule(m2m_ctx);
}
EXPORT_SYMBOL_GPL(v4l2_m2m_request_queue);

/* Videobuf2 ioctl helpers */

int v4l2_m2m_ioctl_reqbufs(struct file *file, void *priv,
                                struct v4l2_requestbuffers *rb)
{
        struct v4l2_fh *fh = file->private_data;

        return v4l2_m2m_reqbufs(file, fh->m2m_ctx, rb);
}
EXPORT_SYMBOL_GPL(v4l2_m2m_ioctl_reqbufs);

int v4l2_m2m_ioctl_create_bufs(struct file *file, void *priv,
                                struct v4l2_create_buffers *create)
{
        struct v4l2_fh *fh = file->private_data;

        return v4l2_m2m_create_bufs(file, fh->m2m_ctx, create);
}
EXPORT_SYMBOL_GPL(v4l2_m2m_ioctl_create_bufs);

int v4l2_m2m_ioctl_querybuf(struct file *file, void *priv,
                                struct v4l2_buffer *buf)
{
        struct v4l2_fh *fh = file->private_data;

        return v4l2_m2m_querybuf(file, fh->m2m_ctx, buf);
}
EXPORT_SYMBOL_GPL(v4l2_m2m_ioctl_querybuf);

int v4l2_m2m_ioctl_qbuf(struct file *file, void *priv,
                                struct v4l2_buffer *buf)
{
        struct v4l2_fh *fh = file->private_data;

        return v4l2_m2m_qbuf(file, fh->m2m_ctx, buf);
}
EXPORT_SYMBOL_GPL(v4l2_m2m_ioctl_qbuf);

int v4l2_m2m_ioctl_dqbuf(struct file *file, void *priv,
                                struct v4l2_buffer *buf)
{
        struct v4l2_fh *fh = file->private_data;

        return v4l2_m2m_dqbuf(file, fh->m2m_ctx, buf);
}
EXPORT_SYMBOL_GPL(v4l2_m2m_ioctl_dqbuf);

int v4l2_m2m_ioctl_prepare_buf(struct file *file, void *priv,
                               struct v4l2_buffer *buf)
{
        struct v4l2_fh *fh = file->private_data;

        return v4l2_m2m_prepare_buf(file, fh->m2m_ctx, buf);
}
EXPORT_SYMBOL_GPL(v4l2_m2m_ioctl_prepare_buf);

int v4l2_m2m_ioctl_expbuf(struct file *file, void *priv,
                                struct v4l2_exportbuffer *eb)
{
        struct v4l2_fh *fh = file->private_data;

        return v4l2_m2m_expbuf(file, fh->m2m_ctx, eb);
}
EXPORT_SYMBOL_GPL(v4l2_m2m_ioctl_expbuf);

int v4l2_m2m_ioctl_streamon(struct file *file, void *priv,
                                enum v4l2_buf_type type)
{
        struct v4l2_fh *fh = file->private_data;

        return v4l2_m2m_streamon(file, fh->m2m_ctx, type);
}
EXPORT_SYMBOL_GPL(v4l2_m2m_ioctl_streamon);

int v4l2_m2m_ioctl_streamoff(struct file *file, void *priv,
                                enum v4l2_buf_type type)
{
        struct v4l2_fh *fh = file->private_data;

        return v4l2_m2m_streamoff(file, fh->m2m_ctx, type);
}
EXPORT_SYMBOL_GPL(v4l2_m2m_ioctl_streamoff);

int v4l2_m2m_ioctl_try_encoder_cmd(struct file *file, void *fh,
                                   struct v4l2_encoder_cmd *ec)
{
        if (ec->cmd != V4L2_ENC_CMD_STOP && ec->cmd != V4L2_ENC_CMD_START)
                return -EINVAL;

        ec->flags = 0;
        return 0;
}
EXPORT_SYMBOL_GPL(v4l2_m2m_ioctl_try_encoder_cmd);

int v4l2_m2m_ioctl_try_decoder_cmd(struct file *file, void *fh,
                                   struct v4l2_decoder_cmd *dc)
{
        if (dc->cmd != V4L2_DEC_CMD_STOP && dc->cmd != V4L2_DEC_CMD_START)
                return -EINVAL;

        dc->flags = 0;

        if (dc->cmd == V4L2_DEC_CMD_STOP) {
                dc->stop.pts = 0;
        } else if (dc->cmd == V4L2_DEC_CMD_START) {
                dc->start.speed = 0;
                dc->start.format = V4L2_DEC_START_FMT_NONE;
        }
        return 0;
}
EXPORT_SYMBOL_GPL(v4l2_m2m_ioctl_try_decoder_cmd);

/*
 * Updates the encoding state on ENC_CMD_STOP/ENC_CMD_START
 * Should be called from the encoder driver encoder_cmd() callback
 */
int v4l2_m2m_encoder_cmd(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
                         struct v4l2_encoder_cmd *ec)
{
        if (ec->cmd != V4L2_ENC_CMD_STOP && ec->cmd != V4L2_ENC_CMD_START)
                return -EINVAL;

        if (ec->cmd == V4L2_ENC_CMD_STOP)
                return v4l2_update_last_buf_state(m2m_ctx);

        if (m2m_ctx->is_draining)
                return -EBUSY;

        if (m2m_ctx->has_stopped)
                m2m_ctx->has_stopped = false;

        return 0;
}
EXPORT_SYMBOL_GPL(v4l2_m2m_encoder_cmd);

/*
 * Updates the decoding state on DEC_CMD_STOP/DEC_CMD_START
 * Should be called from the decoder driver decoder_cmd() callback
 */
int v4l2_m2m_decoder_cmd(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
                         struct v4l2_decoder_cmd *dc)
{
        if (dc->cmd != V4L2_DEC_CMD_STOP && dc->cmd != V4L2_DEC_CMD_START)
                return -EINVAL;

        if (dc->cmd == V4L2_DEC_CMD_STOP)
                return v4l2_update_last_buf_state(m2m_ctx);

        if (m2m_ctx->is_draining)
                return -EBUSY;

        if (m2m_ctx->has_stopped)
                m2m_ctx->has_stopped = false;

        return 0;
}
EXPORT_SYMBOL_GPL(v4l2_m2m_decoder_cmd);

int v4l2_m2m_ioctl_encoder_cmd(struct file *file, void *priv,
                               struct v4l2_encoder_cmd *ec)
{
        struct v4l2_fh *fh = file->private_data;

        return v4l2_m2m_encoder_cmd(file, fh->m2m_ctx, ec);
}
EXPORT_SYMBOL_GPL(v4l2_m2m_ioctl_encoder_cmd);

int v4l2_m2m_ioctl_decoder_cmd(struct file *file, void *priv,
                               struct v4l2_decoder_cmd *dc)
{
        struct v4l2_fh *fh = file->private_data;

        return v4l2_m2m_decoder_cmd(file, fh->m2m_ctx, dc);
}
EXPORT_SYMBOL_GPL(v4l2_m2m_ioctl_decoder_cmd);

int v4l2_m2m_ioctl_stateless_try_decoder_cmd(struct file *file, void *fh,
                                             struct v4l2_decoder_cmd *dc)
{
        if (dc->cmd != V4L2_DEC_CMD_FLUSH)
                return -EINVAL;

        dc->flags = 0;

        return 0;
}
EXPORT_SYMBOL_GPL(v4l2_m2m_ioctl_stateless_try_decoder_cmd);

int v4l2_m2m_ioctl_stateless_decoder_cmd(struct file *file, void *priv,
                                         struct v4l2_decoder_cmd *dc)
{
        struct v4l2_fh *fh = file->private_data;
        struct vb2_v4l2_buffer *out_vb, *cap_vb;
        struct v4l2_m2m_dev *m2m_dev = fh->m2m_ctx->m2m_dev;
        unsigned long flags;
        int ret;

        ret = v4l2_m2m_ioctl_stateless_try_decoder_cmd(file, priv, dc);
        if (ret < 0)
                return ret;

        spin_lock_irqsave(&m2m_dev->job_spinlock, flags);
        out_vb = v4l2_m2m_last_src_buf(fh->m2m_ctx);
        cap_vb = v4l2_m2m_last_dst_buf(fh->m2m_ctx);

        /*
         * If there is an out buffer pending, then clear any HOLD flag.
         *
         * By clearing this flag we ensure that when this output
         * buffer is processed any held capture buffer will be released.
         */
        if (out_vb) {
                out_vb->flags &= ~V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF;
        } else if (cap_vb && cap_vb->is_held) {
                /*
                 * If there were no output buffers, but there is a
                 * capture buffer that is held, then release that
                 * buffer.
                 */
                cap_vb->is_held = false;
                v4l2_m2m_dst_buf_remove(fh->m2m_ctx);
                v4l2_m2m_buf_done(cap_vb, VB2_BUF_STATE_DONE);
        }
        spin_unlock_irqrestore(&m2m_dev->job_spinlock, flags);

        return 0;
}
EXPORT_SYMBOL_GPL(v4l2_m2m_ioctl_stateless_decoder_cmd);

/*
 * v4l2_file_operations helpers. It is assumed here same lock is used
 * for the output and the capture buffer queue.
 */

int v4l2_m2m_fop_mmap(struct file *file, struct vm_area_struct *vma)
{
        struct v4l2_fh *fh = file->private_data;

        return v4l2_m2m_mmap(file, fh->m2m_ctx, vma);
}
EXPORT_SYMBOL_GPL(v4l2_m2m_fop_mmap);

__poll_t v4l2_m2m_fop_poll(struct file *file, poll_table *wait)
{
        struct v4l2_fh *fh = file->private_data;
        struct v4l2_m2m_ctx *m2m_ctx = fh->m2m_ctx;
        __poll_t ret;

        if (m2m_ctx->q_lock)
                mutex_lock(m2m_ctx->q_lock);

        ret = v4l2_m2m_poll(file, m2m_ctx, wait);

        if (m2m_ctx->q_lock)
                mutex_unlock(m2m_ctx->q_lock);

        return ret;
}
EXPORT_SYMBOL_GPL(v4l2_m2m_fop_poll);