V4L/DVB: add memory-to-memory device helper framework for videobuf

A mem-to-mem device is a device that uses memory buffers passed by
userspace applications for both their source and destination data. This
is different from existing drivers, which utilize memory buffers for either
input or output, but not both.

In terms of V4L2 such a device would be both of OUTPUT and CAPTURE type.

Examples of such devices would be: image 'resizers', 'rotators',
'colorspace converters', etc.

This patch adds a separate Kconfig sub-menu for mem-to-mem devices as well.

Signed-off-by: Pawel Osciak <p.osciak@samsung.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Vaibhav Hiremath <hvaibhav@ti.com>
Tested-by: Vaibhav Hiremath <hvaibhav@ti.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

3 files changed, 649 insertions, 0 deletions

diff --git a/drivers/media/video/Kconfig b/drivers/media/video/Kconfig
index 747f106e7b53..f8cbd4adebfd 100644
--- a/drivers/media/video/Kconfig
+++ b/drivers/media/video/Kconfig
@@ -45,6 +45,10 @@ config VIDEO_TUNER
         tristate
         depends on MEDIA_TUNER
 
+config V4L2_MEM2MEM_DEV
+        tristate
+        depends on VIDEOBUF_GEN
+
 #
 # Multimedia Video device configuration
 #
@@ -1121,3 +1125,13 @@ config USB_S2255
 
 endif # V4L_USB_DRIVERS
 endif # VIDEO_CAPTURE_DRIVERS
+
+menuconfig V4L_MEM2MEM_DRIVERS
+        bool "Memory-to-memory multimedia devices"
+        depends on VIDEO_V4L2
+        default n
+        ---help---
+          Say Y here to enable selecting drivers for V4L devices that
+          use system memory for both source and destination buffers, as opposed
+          to capture and output drivers, which use memory buffers for just
+          one of those.
diff --git a/drivers/media/video/Makefile b/drivers/media/video/Makefile
index 4555f5f31ff0..b57be2f542e8 100644
--- a/drivers/media/video/Makefile
+++ b/drivers/media/video/Makefile
@@ -117,6 +117,8 @@ obj-$(CONFIG_VIDEOBUF_VMALLOC) += videobuf-vmalloc.o
 obj-$(CONFIG_VIDEOBUF_DVB) += videobuf-dvb.o
 obj-$(CONFIG_VIDEO_BTCX)  += btcx-risc.o
 
+obj-$(CONFIG_V4L2_MEM2MEM_DEV) += v4l2-mem2mem.o
+
 obj-$(CONFIG_VIDEO_M32R_AR_M64278) += arv.o
 
 obj-$(CONFIG_VIDEO_CX2341X) += cx2341x.o
diff --git a/drivers/media/video/v4l2-mem2mem.c b/drivers/media/video/v4l2-mem2mem.c
new file mode 100644
index 000000000000..f45f9405ea39
--- /dev/null
+++ b/drivers/media/video/v4l2-mem2mem.c
@@ -0,0 +1,633 @@
+/*
+ * 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, <p.osciak@samsung.com>
+ * Marek Szyprowski, <m.szyprowski@samsung.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; either version 2 of the License, or (at your
+ * option) any later version.
+ */
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+
+#include <media/videobuf-core.h>
+#include <media/v4l2-mem2mem.h>
+
+MODULE_DESCRIPTION("Mem to mem device framework for videobuf");
+MODULE_AUTHOR("Pawel Osciak, <p.osciak@samsung.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)
+
+
+/* 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)
+
+
+/**
+ * struct v4l2_m2m_dev - per-device context
+ * @curr_ctx:           currently running instance
+ * @job_queue:          instances queued to run
+ * @job_spinlock:       protects job_queue
+ * @m2m_ops:            driver callbacks
+ */
+struct v4l2_m2m_dev {
+        struct v4l2_m2m_ctx     *curr_ctx;
+
+        struct list_head        job_queue;
+        spinlock_t              job_spinlock;
+
+        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)
+{
+        switch (type) {
+        case V4L2_BUF_TYPE_VIDEO_CAPTURE:
+                return &m2m_ctx->cap_q_ctx;
+        case V4L2_BUF_TYPE_VIDEO_OUTPUT:
+                return &m2m_ctx->out_q_ctx;
+        default:
+                printk(KERN_ERR "Invalid buffer type\n");
+                return NULL;
+        }
+}
+
+/**
+ * v4l2_m2m_get_vq() - return videobuf_queue for the given type
+ */
+struct videobuf_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);
+
+/**
+ * v4l2_m2m_next_buf() - return next buffer from the list of ready buffers
+ */
+void *v4l2_m2m_next_buf(struct v4l2_m2m_ctx *m2m_ctx, enum v4l2_buf_type type)
+{
+        struct v4l2_m2m_queue_ctx *q_ctx;
+        struct videobuf_buffer *vb = NULL;
+        unsigned long flags;
+
+        q_ctx = get_queue_ctx(m2m_ctx, type);
+        if (!q_ctx)
+                return NULL;
+
+        spin_lock_irqsave(q_ctx->q.irqlock, flags);
+
+        if (list_empty(&q_ctx->rdy_queue))
+                goto end;
+
+        vb = list_entry(q_ctx->rdy_queue.next, struct videobuf_buffer, queue);
+        vb->state = VIDEOBUF_ACTIVE;
+
+end:
+        spin_unlock_irqrestore(q_ctx->q.irqlock, flags);
+        return vb;
+}
+EXPORT_SYMBOL_GPL(v4l2_m2m_next_buf);
+
+/**
+ * v4l2_m2m_buf_remove() - take off a buffer from the list of ready buffers and
+ * return it
+ */
+void *v4l2_m2m_buf_remove(struct v4l2_m2m_ctx *m2m_ctx, enum v4l2_buf_type type)
+{
+        struct v4l2_m2m_queue_ctx *q_ctx;
+        struct videobuf_buffer *vb = NULL;
+        unsigned long flags;
+
+        q_ctx = get_queue_ctx(m2m_ctx, type);
+        if (!q_ctx)
+                return NULL;
+
+        spin_lock_irqsave(q_ctx->q.irqlock, flags);
+        if (!list_empty(&q_ctx->rdy_queue)) {
+                vb = list_entry(q_ctx->rdy_queue.next, struct videobuf_buffer,
+                                queue);
+                list_del(&vb->queue);
+                q_ctx->num_rdy--;
+        }
+        spin_unlock_irqrestore(q_ctx->q.irqlock, flags);
+
+        return vb;
+}
+EXPORT_SYMBOL_GPL(v4l2_m2m_buf_remove);
+
+/*
+ * Scheduling handlers
+ */
+
+/**
+ * v4l2_m2m_get_curr_priv() - return driver private data for the currently
+ * running instance or NULL if no instance is running
+ */
+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
+ *
+ * Get next transaction (if present) from the waiting jobs list and run it.
+ */
+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;
+        }
+
+        m2m_dev->curr_ctx = list_entry(m2m_dev->job_queue.next,
+                                   struct v4l2_m2m_ctx, queue);
+        m2m_dev->curr_ctx->job_flags |= TRANS_RUNNING;
+        spin_unlock_irqrestore(&m2m_dev->job_spinlock, flags);
+
+        m2m_dev->m2m_ops->device_run(m2m_dev->curr_ctx->priv);
+}
+
+/**
+ * v4l2_m2m_try_schedule() - check whether an instance is ready to be added to
+ * the pending job queue and add it if so.
+ * @m2m_ctx:    m2m context assigned to the instance to be checked
+ *
+ * There are three basic requirements an instance has to meet to be able to run:
+ * 1) at least one source buffer has to be queued,
+ * 2) at least one destination buffer has to be queued,
+ * 3) streaming has to be on.
+ *
+ * There may also be additional, custom requirements. In such case the driver
+ * should supply a custom callback (job_ready in v4l2_m2m_ops) that should
+ * return 1 if the instance is ready.
+ * An example of the above could be an instance that requires more than one
+ * src/dst buffer per transaction.
+ */
+static void v4l2_m2m_try_schedule(struct v4l2_m2m_ctx *m2m_ctx)
+{
+        struct v4l2_m2m_dev *m2m_dev;
+        unsigned long flags_job, flags;
+
+        m2m_dev = m2m_ctx->m2m_dev;
+        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 (m2m_ctx->job_flags & TRANS_QUEUED) {
+                spin_unlock_irqrestore(&m2m_dev->job_spinlock, flags_job);
+                dprintk("On job queue already\n");
+                return;
+        }
+
+        spin_lock_irqsave(m2m_ctx->out_q_ctx.q.irqlock, flags);
+        if (list_empty(&m2m_ctx->out_q_ctx.rdy_queue)) {
+                spin_unlock_irqrestore(m2m_ctx->out_q_ctx.q.irqlock, flags);
+                spin_unlock_irqrestore(&m2m_dev->job_spinlock, flags_job);
+                dprintk("No input buffers available\n");
+                return;
+        }
+        if (list_empty(&m2m_ctx->cap_q_ctx.rdy_queue)) {
+                spin_unlock_irqrestore(m2m_ctx->out_q_ctx.q.irqlock, flags);
+                spin_unlock_irqrestore(&m2m_dev->job_spinlock, flags_job);
+                dprintk("No output buffers available\n");
+                return;
+        }
+        spin_unlock_irqrestore(m2m_ctx->out_q_ctx.q.irqlock, flags);
+
+        if (m2m_dev->m2m_ops->job_ready
+                && (!m2m_dev->m2m_ops->job_ready(m2m_ctx->priv))) {
+                spin_unlock_irqrestore(&m2m_dev->job_spinlock, flags_job);
+                dprintk("Driver not ready\n");
+                return;
+        }
+
+        list_add_tail(&m2m_ctx->queue, &m2m_dev->job_queue);
+        m2m_ctx->job_flags |= TRANS_QUEUED;
+
+        spin_unlock_irqrestore(&m2m_dev->job_spinlock, flags_job);
+
+        v4l2_m2m_try_run(m2m_dev);
+}
+
+/**
+ * v4l2_m2m_job_finish() - inform the framework that a job has been finished
+ * and have it clean up
+ *
+ * Called by a driver to yield back the device after it has finished with it.
+ * Should be called as soon as possible after reaching a state which allows
+ * other instances to take control of the device.
+ *
+ * This function has to be called only after device_run() callback has been
+ * called on the driver. To prevent recursion, it should not be called directly
+ * from the device_run() callback though.
+ */
+void v4l2_m2m_job_finish(struct v4l2_m2m_dev *m2m_dev,
+                         struct v4l2_m2m_ctx *m2m_ctx)
+{
+        unsigned long flags;
+
+        spin_lock_irqsave(&m2m_dev->job_spinlock, flags);
+        if (!m2m_dev->curr_ctx || m2m_dev->curr_ctx != m2m_ctx) {
+                spin_unlock_irqrestore(&m2m_dev->job_spinlock, flags);
+                dprintk("Called by an instance not currently running\n");
+                return;
+        }
+
+        list_del(&m2m_dev->curr_ctx->queue);
+        m2m_dev->curr_ctx->job_flags &= ~(TRANS_QUEUED | TRANS_RUNNING);
+        m2m_dev->curr_ctx = NULL;
+
+        spin_unlock_irqrestore(&m2m_dev->job_spinlock, flags);
+
+        /* 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_schedule(m2m_ctx);
+        v4l2_m2m_try_run(m2m_dev);
+}
+EXPORT_SYMBOL(v4l2_m2m_job_finish);
+
+/**
+ * v4l2_m2m_reqbufs() - multi-queue-aware REQBUFS multiplexer
+ */
+int v4l2_m2m_reqbufs(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
+                     struct v4l2_requestbuffers *reqbufs)
+{
+        struct videobuf_queue *vq;
+
+        vq = v4l2_m2m_get_vq(m2m_ctx, reqbufs->type);
+        return videobuf_reqbufs(vq, reqbufs);
+}
+EXPORT_SYMBOL_GPL(v4l2_m2m_reqbufs);
+
+/**
+ * v4l2_m2m_querybuf() - multi-queue-aware QUERYBUF multiplexer
+ *
+ * See v4l2_m2m_mmap() documentation for details.
+ */
+int v4l2_m2m_querybuf(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
+                      struct v4l2_buffer *buf)
+{
+        struct videobuf_queue *vq;
+        int ret;
+
+        vq = v4l2_m2m_get_vq(m2m_ctx, buf->type);
+        ret = videobuf_querybuf(vq, buf);
+
+        if (buf->memory == V4L2_MEMORY_MMAP
+            && vq->type == V4L2_BUF_TYPE_VIDEO_CAPTURE) {
+                buf->m.offset += DST_QUEUE_OFF_BASE;
+        }
+
+        return ret;
+}
+EXPORT_SYMBOL_GPL(v4l2_m2m_querybuf);
+
+/**
+ * v4l2_m2m_qbuf() - enqueue a source or destination buffer, depending on
+ * the type
+ */
+int v4l2_m2m_qbuf(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
+                  struct v4l2_buffer *buf)
+{
+        struct videobuf_queue *vq;
+        int ret;
+
+        vq = v4l2_m2m_get_vq(m2m_ctx, buf->type);
+        ret = videobuf_qbuf(vq, buf);
+        if (!ret)
+                v4l2_m2m_try_schedule(m2m_ctx);
+
+        return ret;
+}
+EXPORT_SYMBOL_GPL(v4l2_m2m_qbuf);
+
+/**
+ * v4l2_m2m_dqbuf() - dequeue a source or destination buffer, depending on
+ * the type
+ */
+int v4l2_m2m_dqbuf(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
+                   struct v4l2_buffer *buf)
+{
+        struct videobuf_queue *vq;
+
+        vq = v4l2_m2m_get_vq(m2m_ctx, buf->type);
+        return videobuf_dqbuf(vq, buf, file->f_flags & O_NONBLOCK);
+}
+EXPORT_SYMBOL_GPL(v4l2_m2m_dqbuf);
+
+/**
+ * v4l2_m2m_streamon() - turn on streaming for a video queue
+ */
+int v4l2_m2m_streamon(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
+                      enum v4l2_buf_type type)
+{
+        struct videobuf_queue *vq;
+        int ret;
+
+        vq = v4l2_m2m_get_vq(m2m_ctx, type);
+        ret = videobuf_streamon(vq);
+        if (!ret)
+                v4l2_m2m_try_schedule(m2m_ctx);
+
+        return ret;
+}
+EXPORT_SYMBOL_GPL(v4l2_m2m_streamon);
+
+/**
+ * v4l2_m2m_streamoff() - turn off streaming for a video queue
+ */
+int v4l2_m2m_streamoff(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
+                       enum v4l2_buf_type type)
+{
+        struct videobuf_queue *vq;
+
+        vq = v4l2_m2m_get_vq(m2m_ctx, type);
+        return videobuf_streamoff(vq);
+}
+EXPORT_SYMBOL_GPL(v4l2_m2m_streamoff);
+
+/**
+ * v4l2_m2m_poll() - poll replacement, for destination buffers only
+ *
+ * Call from the driver's poll() function. Will poll both queues. If a buffer
+ * is available to dequeue (with dqbuf) from the source queue, this will
+ * indicate that a non-blocking write can be performed, while read will be
+ * returned in case of the destination queue.
+ */
+unsigned int v4l2_m2m_poll(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
+                           struct poll_table_struct *wait)
+{
+        struct videobuf_queue *src_q, *dst_q;
+        struct videobuf_buffer *src_vb = NULL, *dst_vb = NULL;
+        unsigned int rc = 0;
+
+        src_q = v4l2_m2m_get_src_vq(m2m_ctx);
+        dst_q = v4l2_m2m_get_dst_vq(m2m_ctx);
+
+        mutex_lock(&src_q->vb_lock);
+        mutex_lock(&dst_q->vb_lock);
+
+        if (src_q->streaming && !list_empty(&src_q->stream))
+                src_vb = list_first_entry(&src_q->stream,
+                                          struct videobuf_buffer, stream);
+        if (dst_q->streaming && !list_empty(&dst_q->stream))
+                dst_vb = list_first_entry(&dst_q->stream,
+                                          struct videobuf_buffer, stream);
+
+        if (!src_vb && !dst_vb) {
+                rc = POLLERR;
+                goto end;
+        }
+
+        if (src_vb) {
+                poll_wait(file, &src_vb->done, wait);
+                if (src_vb->state == VIDEOBUF_DONE
+                    || src_vb->state == VIDEOBUF_ERROR)
+                        rc |= POLLOUT | POLLWRNORM;
+        }
+        if (dst_vb) {
+                poll_wait(file, &dst_vb->done, wait);
+                if (dst_vb->state == VIDEOBUF_DONE
+                    || dst_vb->state == VIDEOBUF_ERROR)
+                        rc |= POLLIN | POLLRDNORM;
+        }
+
+end:
+        mutex_unlock(&dst_q->vb_lock);
+        mutex_unlock(&src_q->vb_lock);
+        return rc;
+}
+EXPORT_SYMBOL_GPL(v4l2_m2m_poll);
+
+/**
+ * v4l2_m2m_mmap() - source and destination queues-aware mmap multiplexer
+ *
+ * Call from driver's mmap() function. Will handle mmap() for both queues
+ * seamlessly for videobuffer, which will receive normal per-queue offsets and
+ * proper videobuf queue pointers. The differentiation is made outside videobuf
+ * by adding a predefined offset to buffers from one of the queues and
+ * subtracting it before passing it back to videobuf. Only drivers (and
+ * thus applications) receive modified offsets.
+ */
+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 videobuf_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 videobuf_mmap_mapper(vq, vma);
+}
+EXPORT_SYMBOL(v4l2_m2m_mmap);
+
+/**
+ * v4l2_m2m_init() - initialize per-driver m2m data
+ *
+ * Usually called from driver's probe() function.
+ */
+struct v4l2_m2m_dev *v4l2_m2m_init(struct v4l2_m2m_ops *m2m_ops)
+{
+        struct v4l2_m2m_dev *m2m_dev;
+
+        if (!m2m_ops)
+                return ERR_PTR(-EINVAL);
+
+        BUG_ON(!m2m_ops->device_run);
+        BUG_ON(!m2m_ops->job_abort);
+
+        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);
+
+        return m2m_dev;
+}
+EXPORT_SYMBOL_GPL(v4l2_m2m_init);
+
+/**
+ * v4l2_m2m_release() - cleans up and frees a m2m_dev structure
+ *
+ * Usually called from driver's remove() function.
+ */
+void v4l2_m2m_release(struct v4l2_m2m_dev *m2m_dev)
+{
+        kfree(m2m_dev);
+}
+EXPORT_SYMBOL_GPL(v4l2_m2m_release);
+
+/**
+ * v4l2_m2m_ctx_init() - allocate and initialize a m2m context
+ * @priv - driver's instance private data
+ * @m2m_dev - a previously initialized m2m_dev struct
+ * @vq_init - a callback for queue type-specific initialization function to be
+ * used for initializing videobuf_queues
+ *
+ * Usually called from driver's open() function.
+ */
+struct v4l2_m2m_ctx *v4l2_m2m_ctx_init(void *priv, struct v4l2_m2m_dev *m2m_dev,
+                        void (*vq_init)(void *priv, struct videobuf_queue *,
+                                        enum v4l2_buf_type))
+{
+        struct v4l2_m2m_ctx *m2m_ctx;
+        struct v4l2_m2m_queue_ctx *out_q_ctx, *cap_q_ctx;
+
+        if (!vq_init)
+                return ERR_PTR(-EINVAL);
+
+        m2m_ctx = kzalloc(sizeof *m2m_ctx, GFP_KERNEL);
+        if (!m2m_ctx)
+                return ERR_PTR(-ENOMEM);
+
+        m2m_ctx->priv = priv;
+        m2m_ctx->m2m_dev = m2m_dev;
+
+        out_q_ctx = get_queue_ctx(m2m_ctx, V4L2_BUF_TYPE_VIDEO_OUTPUT);
+        cap_q_ctx = get_queue_ctx(m2m_ctx, V4L2_BUF_TYPE_VIDEO_CAPTURE);
+
+        INIT_LIST_HEAD(&out_q_ctx->rdy_queue);
+        INIT_LIST_HEAD(&cap_q_ctx->rdy_queue);
+
+        INIT_LIST_HEAD(&m2m_ctx->queue);
+
+        vq_init(priv, &out_q_ctx->q, V4L2_BUF_TYPE_VIDEO_OUTPUT);
+        vq_init(priv, &cap_q_ctx->q, V4L2_BUF_TYPE_VIDEO_CAPTURE);
+        out_q_ctx->q.priv_data = cap_q_ctx->q.priv_data = priv;
+
+        return m2m_ctx;
+}
+EXPORT_SYMBOL_GPL(v4l2_m2m_ctx_init);
+
+/**
+ * v4l2_m2m_ctx_release() - release m2m context
+ *
+ * Usually called from driver's release() function.
+ */
+void v4l2_m2m_ctx_release(struct v4l2_m2m_ctx *m2m_ctx)
+{
+        struct v4l2_m2m_dev *m2m_dev;
+        struct videobuf_buffer *vb;
+        unsigned long flags;
+
+        m2m_dev = m2m_ctx->m2m_dev;
+
+        spin_lock_irqsave(&m2m_dev->job_spinlock, flags);
+        if (m2m_ctx->job_flags & TRANS_RUNNING) {
+                spin_unlock_irqrestore(&m2m_dev->job_spinlock, flags);
+                m2m_dev->m2m_ops->job_abort(m2m_ctx->priv);
+                dprintk("m2m_ctx %p running, will wait to complete", m2m_ctx);
+                vb = v4l2_m2m_next_dst_buf(m2m_ctx);
+                BUG_ON(NULL == vb);
+                wait_event(vb->done, vb->state != VIDEOBUF_ACTIVE
+                                     && vb->state != VIDEOBUF_QUEUED);
+        } 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);
+        }
+
+        videobuf_stop(&m2m_ctx->cap_q_ctx.q);
+        videobuf_stop(&m2m_ctx->out_q_ctx.q);
+
+        videobuf_mmap_free(&m2m_ctx->cap_q_ctx.q);
+        videobuf_mmap_free(&m2m_ctx->out_q_ctx.q);
+
+        kfree(m2m_ctx);
+}
+EXPORT_SYMBOL_GPL(v4l2_m2m_ctx_release);
+
+/**
+ * v4l2_m2m_buf_queue() - add a buffer to the proper ready buffers list.
+ *
+ * Call from buf_queue(), videobuf_queue_ops callback.
+ *
+ * Locking: Caller holds q->irqlock (taken by videobuf before calling buf_queue
+ * callback in the driver).
+ */
+void v4l2_m2m_buf_queue(struct v4l2_m2m_ctx *m2m_ctx, struct videobuf_queue *vq,
+                        struct videobuf_buffer *vb)
+{
+        struct v4l2_m2m_queue_ctx *q_ctx;
+
+        q_ctx = get_queue_ctx(m2m_ctx, vq->type);
+        if (!q_ctx)
+                return;
+
+        list_add_tail(&vb->queue, &q_ctx->rdy_queue);
+        q_ctx->num_rdy++;
+
+        vb->state = VIDEOBUF_QUEUED;
+}
+EXPORT_SYMBOL_GPL(v4l2_m2m_buf_queue);
+