[RFC,v8,13/13] media: vim2m_audio: add virtual driver for audio memory to memory

Audio memory to memory virtual driver use video memory to memory
virtual driver vim2m.c as example. The main difference is
device type is VFL_TYPE_AUDIO and device cap type is V4L2_CAP_AUDIO_M2M.

The device_run function is a dummy function, which is simply
copy the data from input buffer to output buffer.

Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
---
 drivers/media/test-drivers/Kconfig       |   9 +
 drivers/media/test-drivers/Makefile      |   1 +
 drivers/media/test-drivers/vim2m_audio.c | 680 +++++++++++++++++++++++
 3 files changed, 690 insertions(+)
 create mode 100644 drivers/media/test-drivers/vim2m_audio.c

On 27/10/2023 12:35, Shengjiu Wang wrote:
> Audio memory to memory virtual driver use video memory to memory
> virtual driver vim2m.c as example. The main difference is
> device type is VFL_TYPE_AUDIO and device cap type is V4L2_CAP_AUDIO_M2M.
> 
> The device_run function is a dummy function, which is simply
> copy the data from input buffer to output buffer.

I started work on the v4l-utils part of this, using this driver.

I noticed that this driver doesn't expose the V4L2_CID_M2M_AUDIO_SOURCE/SINK_RATE
controls, and it really should, otherwise it is not representative of this
type of device.

It is enough to start with just a single fixed rate listed for each control.

It would be even nicer if you can have two rates such as 24000 and 48000 and
do the actual rate conversion, i.e. dropping every other sample or duplicating
each sample depending on whether you're halving or doubling the rate. That
should be easy to implement, and it makes this driver much more realistic.

Regards,

	Hans

> 
> Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
> ---
>  drivers/media/test-drivers/Kconfig       |   9 +
>  drivers/media/test-drivers/Makefile      |   1 +
>  drivers/media/test-drivers/vim2m_audio.c | 680 +++++++++++++++++++++++
>  3 files changed, 690 insertions(+)
>  create mode 100644 drivers/media/test-drivers/vim2m_audio.c
> 
> diff --git a/drivers/media/test-drivers/Kconfig b/drivers/media/test-drivers/Kconfig
> index 459b433e9fae..c280e192d43a 100644
> --- a/drivers/media/test-drivers/Kconfig
> +++ b/drivers/media/test-drivers/Kconfig
> @@ -17,6 +17,15 @@ config VIDEO_VIM2M
>  	  This is a virtual test device for the memory-to-memory driver
>  	  framework.
>  
> +config VIDEO_VIM2M_AUDIO
> +	tristate "Virtual Memory-to-Memory Driver For Audio"
> +	depends on VIDEO_DEV
> +	select VIDEOBUF2_VMALLOC
> +	select V4L2_MEM2MEM_DEV
> +	help
> +	  This is a virtual audio test device for the memory-to-memory driver
> +	  framework.
> +
>  source "drivers/media/test-drivers/vicodec/Kconfig"
>  source "drivers/media/test-drivers/vimc/Kconfig"
>  source "drivers/media/test-drivers/vivid/Kconfig"
> diff --git a/drivers/media/test-drivers/Makefile b/drivers/media/test-drivers/Makefile
> index 740714a4584d..c2c33282bf96 100644
> --- a/drivers/media/test-drivers/Makefile
> +++ b/drivers/media/test-drivers/Makefile
> @@ -10,6 +10,7 @@ obj-$(CONFIG_DVB_VIDTV) += vidtv/
>  
>  obj-$(CONFIG_VIDEO_VICODEC) += vicodec/
>  obj-$(CONFIG_VIDEO_VIM2M) += vim2m.o
> +obj-$(CONFIG_VIDEO_VIM2M_AUDIO) += vim2m_audio.o
>  obj-$(CONFIG_VIDEO_VIMC) += vimc/
>  obj-$(CONFIG_VIDEO_VIVID) += vivid/
>  obj-$(CONFIG_VIDEO_VISL) += visl/
> diff --git a/drivers/media/test-drivers/vim2m_audio.c b/drivers/media/test-drivers/vim2m_audio.c
> new file mode 100644
> index 000000000000..2134e8338417
> --- /dev/null
> +++ b/drivers/media/test-drivers/vim2m_audio.c
> @@ -0,0 +1,680 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * A virtual v4l2-mem2mem example for audio device.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/delay.h>
> +#include <linux/fs.h>
> +#include <linux/sched.h>
> +#include <linux/slab.h>
> +
> +#include <linux/platform_device.h>
> +#include <media/v4l2-mem2mem.h>
> +#include <media/v4l2-device.h>
> +#include <media/v4l2-ioctl.h>
> +#include <media/v4l2-ctrls.h>
> +#include <media/v4l2-event.h>
> +#include <media/videobuf2-vmalloc.h>
> +#include <sound/dmaengine_pcm.h>
> +
> +MODULE_DESCRIPTION("Virtual device for audio mem2mem testing");
> +MODULE_LICENSE("GPL");
> +
> +static unsigned int debug;
> +module_param(debug, uint, 0644);
> +MODULE_PARM_DESC(debug, "debug level");
> +
> +#define MEM2MEM_NAME "vim2m-audio"
> +
> +#define dprintk(dev, lvl, fmt, arg...) \
> +	v4l2_dbg(lvl, debug, &(dev)->v4l2_dev, "%s: " fmt, __func__, ## arg)
> +
> +#define SAMPLE_NUM 4096
> +
> +static void audm2m_dev_release(struct device *dev)
> +{}
> +
> +static struct platform_device audm2m_pdev = {
> +	.name		= MEM2MEM_NAME,
> +	.dev.release	= audm2m_dev_release,
> +};
> +
> +static u32 formats[] = {
> +	V4L2_AUDIO_FMT_S8,
> +	V4L2_AUDIO_FMT_S16_LE,
> +	V4L2_AUDIO_FMT_U16_LE,
> +	V4L2_AUDIO_FMT_S24_LE,
> +	V4L2_AUDIO_FMT_S24_3LE,
> +	V4L2_AUDIO_FMT_U24_LE,
> +	V4L2_AUDIO_FMT_U24_3LE,
> +	V4L2_AUDIO_FMT_S32_LE,
> +	V4L2_AUDIO_FMT_U32_LE,
> +	V4L2_AUDIO_FMT_S20_3LE,
> +	V4L2_AUDIO_FMT_U20_3LE,
> +};
> +
> +#define NUM_FORMATS ARRAY_SIZE(formats)
> +
> +/* Per-queue, driver-specific private data */
> +struct audm2m_q_data {
> +	unsigned int		rate;
> +	unsigned int		channels;
> +	unsigned int		buffersize;
> +	u32			fourcc;
> +};
> +
> +enum {
> +	V4L2_M2M_SRC = 0,
> +	V4L2_M2M_DST = 1,
> +};
> +
> +static snd_pcm_format_t find_format(u32 fourcc)
> +{
> +	snd_pcm_format_t fmt;
> +	unsigned int k;
> +
> +	for (k = 0; k < NUM_FORMATS; k++) {
> +		if (formats[k] == fourcc)
> +			break;
> +	}
> +
> +	if (k == NUM_FORMATS)
> +		return 0;
> +
> +	fmt = v4l2_fourcc_to_audfmt(formats[k]);
> +
> +	return fmt;
> +}
> +
> +struct audm2m_dev {
> +	struct v4l2_device	v4l2_dev;
> +	struct video_device	vfd;
> +
> +	struct mutex		dev_mutex;
> +
> +	struct v4l2_m2m_dev	*m2m_dev;
> +};
> +
> +struct audm2m_ctx {
> +	struct v4l2_fh		fh;
> +	struct audm2m_dev	*dev;
> +
> +	struct mutex		vb_mutex;
> +
> +	/* Source and destination queue data */
> +	struct audm2m_q_data   q_data[2];
> +};
> +
> +static inline struct audm2m_ctx *file2ctx(struct file *file)
> +{
> +	return container_of(file->private_data, struct audm2m_ctx, fh);
> +}
> +
> +static struct audm2m_q_data *get_q_data(struct audm2m_ctx *ctx,
> +					enum v4l2_buf_type type)
> +{
> +	if (type == V4L2_BUF_TYPE_AUDIO_OUTPUT)
> +		return &ctx->q_data[V4L2_M2M_SRC];
> +	return &ctx->q_data[V4L2_M2M_DST];
> +}
> +
> +static const char *type_name(enum v4l2_buf_type type)
> +{
> +	if (type == V4L2_BUF_TYPE_AUDIO_OUTPUT)
> +		return "Output";
> +	return "Capture";
> +}
> +
> +/*
> + * mem2mem callbacks
> + */
> +
> +/*
> + * device_run() - prepares and starts the device
> + */
> +static void device_run(void *priv)
> +{
> +	struct audm2m_ctx *ctx = priv;
> +	struct audm2m_dev *audm2m_dev;
> +	struct vb2_v4l2_buffer *src_buf, *dst_buf;
> +	struct audm2m_q_data *q_data_src, *q_data_dst;
> +	int src_size, dst_size;
> +
> +	audm2m_dev = ctx->dev;
> +
> +	q_data_src = get_q_data(ctx, V4L2_BUF_TYPE_AUDIO_OUTPUT);
> +	if (!q_data_src)
> +		return;
> +
> +	q_data_dst = get_q_data(ctx, V4L2_BUF_TYPE_AUDIO_CAPTURE);
> +	if (!q_data_dst)
> +		return;
> +
> +	src_buf = v4l2_m2m_next_src_buf(ctx->fh.m2m_ctx);
> +	dst_buf = v4l2_m2m_next_dst_buf(ctx->fh.m2m_ctx);
> +
> +	/* Process the conversion */
> +	src_size = vb2_get_plane_payload(&src_buf->vb2_buf, 0);
> +
> +	if (src_size > q_data_dst->buffersize)
> +		dst_size = q_data_dst->buffersize;
> +	else
> +		dst_size = src_size;
> +
> +	memcpy(vb2_plane_vaddr(&dst_buf->vb2_buf, 0),
> +	       vb2_plane_vaddr(&src_buf->vb2_buf, 0),
> +	       dst_size);
> +
> +	vb2_set_plane_payload(&dst_buf->vb2_buf, 0, dst_size);
> +
> +	src_buf = v4l2_m2m_src_buf_remove(ctx->fh.m2m_ctx);
> +	dst_buf = v4l2_m2m_dst_buf_remove(ctx->fh.m2m_ctx);
> +
> +	v4l2_m2m_buf_done(src_buf, VB2_BUF_STATE_DONE);
> +	v4l2_m2m_buf_done(dst_buf, VB2_BUF_STATE_DONE);
> +	v4l2_m2m_job_finish(audm2m_dev->m2m_dev, ctx->fh.m2m_ctx);
> +}
> +
> +static int audm2m_querycap(struct file *file, void *priv,
> +			   struct v4l2_capability *cap)
> +{
> +	strscpy(cap->driver, MEM2MEM_NAME, sizeof(cap->driver));
> +	strscpy(cap->card, MEM2MEM_NAME, sizeof(cap->card));
> +	snprintf(cap->bus_info, sizeof(cap->bus_info),
> +		 "platform:%s", MEM2MEM_NAME);
> +
> +	return 0;
> +}
> +
> +static int enum_fmt(struct v4l2_fmtdesc *f)
> +{
> +	int i, num;
> +
> +	num = 0;
> +
> +	for (i = 0; i < NUM_FORMATS; ++i) {
> +		if (num == f->index)
> +			break;
> +		/*
> +		 * Correct type but haven't reached our index yet,
> +		 * just increment per-type index
> +		 */
> +		++num;
> +	}
> +
> +	if (i < NUM_FORMATS) {
> +		/* Format found */
> +		f->pixelformat = formats[i];
> +		return 0;
> +	}
> +
> +	/* Format not found */
> +	return -EINVAL;
> +}
> +
> +static int audm2m_enum_fmt_audio_cap(struct file *file, void *priv,
> +				     struct v4l2_fmtdesc *f)
> +{
> +	return enum_fmt(f);
> +}
> +
> +static int audm2m_enum_fmt_audio_out(struct file *file, void *priv,
> +				     struct v4l2_fmtdesc *f)
> +{
> +	return enum_fmt(f);
> +}
> +
> +static int audm2m_g_fmt(struct audm2m_ctx *ctx, struct v4l2_format *f)
> +{
> +	struct vb2_queue *vq;
> +	struct audm2m_q_data *q_data;
> +
> +	vq = v4l2_m2m_get_vq(ctx->fh.m2m_ctx, f->type);
> +	if (!vq)
> +		return -EINVAL;
> +
> +	q_data = get_q_data(ctx, f->type);
> +	if (!q_data)
> +		return -EINVAL;
> +
> +	f->fmt.audio.audioformat = q_data->fourcc;
> +	f->fmt.audio.channels	= q_data->channels;
> +	f->fmt.audio.buffersize = q_data->buffersize;
> +
> +	return 0;
> +}
> +
> +static int audm2m_g_fmt_audio_out(struct file *file, void *priv,
> +				  struct v4l2_format *f)
> +{
> +	return audm2m_g_fmt(file2ctx(file), f);
> +}
> +
> +static int audm2m_g_fmt_audio_cap(struct file *file, void *priv,
> +				  struct v4l2_format *f)
> +{
> +	return audm2m_g_fmt(file2ctx(file), f);
> +}
> +
> +static int audm2m_try_fmt(struct v4l2_format *f, snd_pcm_format_t fmt)
> +{
> +	if (f->fmt.audio.channels < 1)
> +		f->fmt.audio.channels = 1;
> +	else if (f->fmt.audio.channels > 8)
> +		f->fmt.audio.channels = 8;
> +
> +	f->fmt.audio.buffersize = f->fmt.audio.channels *
> +				  snd_pcm_format_physical_width(fmt) *
> +				  SAMPLE_NUM;
> +	return 0;
> +}
> +
> +static int audm2m_try_fmt_audio_cap(struct file *file, void *priv,
> +				    struct v4l2_format *f)
> +{
> +	snd_pcm_format_t fmt;
> +
> +	fmt = find_format(f->fmt.audio.audioformat);
> +	if (!fmt) {
> +		f->fmt.audio.audioformat = formats[0];
> +		fmt = find_format(f->fmt.audio.audioformat);
> +	}
> +
> +	return audm2m_try_fmt(f, fmt);
> +}
> +
> +static int audm2m_try_fmt_audio_out(struct file *file, void *priv,
> +				    struct v4l2_format *f)
> +{
> +	snd_pcm_format_t fmt;
> +
> +	fmt = find_format(f->fmt.audio.audioformat);
> +	if (!fmt) {
> +		f->fmt.audio.audioformat = formats[0];
> +		fmt = find_format(f->fmt.audio.audioformat);
> +	}
> +
> +	return audm2m_try_fmt(f, fmt);
> +}
> +
> +static int audm2m_s_fmt(struct audm2m_ctx *ctx, struct v4l2_format *f)
> +{
> +	struct audm2m_q_data *q_data;
> +	struct vb2_queue *vq;
> +	snd_pcm_format_t fmt;
> +
> +	vq = v4l2_m2m_get_vq(ctx->fh.m2m_ctx, f->type);
> +	if (!vq)
> +		return -EINVAL;
> +
> +	q_data = get_q_data(ctx, f->type);
> +	if (!q_data)
> +		return -EINVAL;
> +
> +	if (vb2_is_busy(vq)) {
> +		v4l2_err(&ctx->dev->v4l2_dev, "%s queue busy\n", __func__);
> +		return -EBUSY;
> +	}
> +
> +	q_data->fourcc	= f->fmt.audio.audioformat;
> +	q_data->channels = f->fmt.audio.channels;
> +
> +	fmt = find_format(f->fmt.audio.audioformat);
> +	q_data->buffersize = q_data->channels *
> +			     snd_pcm_format_physical_width(fmt) *
> +			     SAMPLE_NUM;
> +
> +	dprintk(ctx->dev, 1,
> +		"Format for type %s: %d/%d, fmt: %c%c%c%c\n",
> +		type_name(f->type), q_data->rate,
> +		q_data->channels,
> +		(q_data->fourcc & 0xff),
> +		(q_data->fourcc >>  8) & 0xff,
> +		(q_data->fourcc >> 16) & 0xff,
> +		(q_data->fourcc >> 24) & 0xff);
> +
> +	return 0;
> +}
> +
> +static int audm2m_s_fmt_audio_cap(struct file *file, void *priv,
> +				  struct v4l2_format *f)
> +{
> +	int ret;
> +
> +	ret = audm2m_try_fmt_audio_cap(file, priv, f);
> +	if (ret)
> +		return ret;
> +
> +	return audm2m_s_fmt(file2ctx(file), f);
> +}
> +
> +static int audm2m_s_fmt_audio_out(struct file *file, void *priv,
> +				  struct v4l2_format *f)
> +{
> +	int ret;
> +
> +	ret = audm2m_try_fmt_audio_out(file, priv, f);
> +	if (ret)
> +		return ret;
> +
> +	return audm2m_s_fmt(file2ctx(file), f);
> +}
> +
> +static const struct v4l2_ioctl_ops audm2m_ioctl_ops = {
> +	.vidioc_querycap		= audm2m_querycap,
> +
> +	.vidioc_enum_fmt_audio_cap	= audm2m_enum_fmt_audio_cap,
> +	.vidioc_g_fmt_audio_cap		= audm2m_g_fmt_audio_cap,
> +	.vidioc_try_fmt_audio_cap	= audm2m_try_fmt_audio_cap,
> +	.vidioc_s_fmt_audio_cap		= audm2m_s_fmt_audio_cap,
> +
> +	.vidioc_enum_fmt_audio_out	= audm2m_enum_fmt_audio_out,
> +	.vidioc_g_fmt_audio_out		= audm2m_g_fmt_audio_out,
> +	.vidioc_try_fmt_audio_out	= audm2m_try_fmt_audio_out,
> +	.vidioc_s_fmt_audio_out		= audm2m_s_fmt_audio_out,
> +
> +	.vidioc_reqbufs			= v4l2_m2m_ioctl_reqbufs,
> +	.vidioc_querybuf		= v4l2_m2m_ioctl_querybuf,
> +	.vidioc_qbuf			= v4l2_m2m_ioctl_qbuf,
> +	.vidioc_dqbuf			= v4l2_m2m_ioctl_dqbuf,
> +	.vidioc_prepare_buf		= v4l2_m2m_ioctl_prepare_buf,
> +	.vidioc_create_bufs		= v4l2_m2m_ioctl_create_bufs,
> +	.vidioc_expbuf			= v4l2_m2m_ioctl_expbuf,
> +
> +	.vidioc_streamon		= v4l2_m2m_ioctl_streamon,
> +	.vidioc_streamoff		= v4l2_m2m_ioctl_streamoff,
> +
> +	.vidioc_subscribe_event		= v4l2_ctrl_subscribe_event,
> +	.vidioc_unsubscribe_event	= v4l2_event_unsubscribe,
> +};
> +
> +/*
> + * Queue operations
> + */
> +static int audm2m_queue_setup(struct vb2_queue *vq,
> +			      unsigned int *nbuffers,
> +			      unsigned int *nplanes,
> +			      unsigned int sizes[],
> +			      struct device *alloc_devs[])
> +{
> +	struct audm2m_ctx *ctx = vb2_get_drv_priv(vq);
> +	struct audm2m_q_data *q_data;
> +
> +	q_data = get_q_data(ctx, vq->type);
> +
> +	if (*nplanes)
> +		return sizes[0] < q_data->buffersize ? -EINVAL : 0;
> +
> +	*nplanes = 1;
> +	sizes[0] = q_data->buffersize;
> +
> +	dprintk(ctx->dev, 1, "%s: get %d buffer(s) of size %d each.\n",
> +		type_name(vq->type), *nplanes, sizes[0]);
> +
> +	return 0;
> +}
> +
> +static void audm2m_buf_queue(struct vb2_buffer *vb)
> +{
> +	struct vb2_v4l2_buffer *vbuf = to_vb2_v4l2_buffer(vb);
> +	struct audm2m_ctx *ctx = vb2_get_drv_priv(vb->vb2_queue);
> +
> +	v4l2_m2m_buf_queue(ctx->fh.m2m_ctx, vbuf);
> +}
> +
> +static void audm2m_stop_streaming(struct vb2_queue *q)
> +{
> +	struct audm2m_ctx *ctx = vb2_get_drv_priv(q);
> +	struct vb2_v4l2_buffer *vbuf;
> +
> +	for (;;) {
> +		if (V4L2_TYPE_IS_OUTPUT(q->type))
> +			vbuf = v4l2_m2m_src_buf_remove(ctx->fh.m2m_ctx);
> +		else
> +			vbuf = v4l2_m2m_dst_buf_remove(ctx->fh.m2m_ctx);
> +		if (!vbuf)
> +			return;
> +		v4l2_m2m_buf_done(vbuf, VB2_BUF_STATE_ERROR);
> +	}
> +}
> +
> +static const struct vb2_ops audm2m_qops = {
> +	.queue_setup	 = audm2m_queue_setup,
> +	.buf_queue	 = audm2m_buf_queue,
> +	.stop_streaming  = audm2m_stop_streaming,
> +	.wait_prepare	 = vb2_ops_wait_prepare,
> +	.wait_finish	 = vb2_ops_wait_finish,
> +};
> +
> +static int queue_init(void *priv, struct vb2_queue *src_vq,
> +		      struct vb2_queue *dst_vq)
> +{
> +	struct audm2m_ctx *ctx = priv;
> +	int ret;
> +
> +	src_vq->type = V4L2_BUF_TYPE_AUDIO_OUTPUT;
> +	src_vq->io_modes = VB2_MMAP | VB2_DMABUF;
> +	src_vq->drv_priv = ctx;
> +	src_vq->buf_struct_size = sizeof(struct v4l2_m2m_buffer);
> +	src_vq->ops = &audm2m_qops;
> +	src_vq->mem_ops = &vb2_vmalloc_memops;
> +	src_vq->timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_COPY;
> +	src_vq->lock = &ctx->vb_mutex;
> +	src_vq->min_buffers_needed = 1;
> +
> +	ret = vb2_queue_init(src_vq);
> +	if (ret)
> +		return ret;
> +
> +	dst_vq->type = V4L2_BUF_TYPE_AUDIO_CAPTURE;
> +	dst_vq->io_modes = VB2_MMAP | VB2_DMABUF;
> +	dst_vq->drv_priv = ctx;
> +	dst_vq->buf_struct_size = sizeof(struct v4l2_m2m_buffer);
> +	dst_vq->ops = &audm2m_qops;
> +	dst_vq->mem_ops = &vb2_vmalloc_memops;
> +	dst_vq->timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_COPY;
> +	dst_vq->lock = &ctx->vb_mutex;
> +	dst_vq->min_buffers_needed = 1;
> +
> +	return vb2_queue_init(dst_vq);
> +}
> +
> +/*
> + * File operations
> + */
> +static int audm2m_open(struct file *file)
> +{
> +	struct audm2m_dev *dev = video_drvdata(file);
> +	struct audm2m_ctx *ctx = NULL;
> +	snd_pcm_format_t fmt;
> +	int width;
> +	int rc = 0;
> +
> +	if (mutex_lock_interruptible(&dev->dev_mutex))
> +		return -ERESTARTSYS;
> +	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
> +	if (!ctx) {
> +		rc = -ENOMEM;
> +		goto open_unlock;
> +	}
> +
> +	v4l2_fh_init(&ctx->fh, video_devdata(file));
> +	file->private_data = &ctx->fh;
> +	ctx->dev = dev;
> +
> +	ctx->q_data[V4L2_M2M_SRC].fourcc = formats[0];
> +	ctx->q_data[V4L2_M2M_SRC].rate = 8000;
> +	ctx->q_data[V4L2_M2M_SRC].channels = 2;
> +
> +	/* Fix to 4096 samples */
> +	fmt = find_format(formats[0]);
> +	width = snd_pcm_format_physical_width(fmt);
> +	ctx->q_data[V4L2_M2M_SRC].buffersize = SAMPLE_NUM * 2 * width;
> +	ctx->q_data[V4L2_M2M_DST] = ctx->q_data[V4L2_M2M_SRC];
> +
> +	ctx->fh.m2m_ctx = v4l2_m2m_ctx_init(dev->m2m_dev, ctx, &queue_init);
> +
> +	mutex_init(&ctx->vb_mutex);
> +
> +	if (IS_ERR(ctx->fh.m2m_ctx)) {
> +		rc = PTR_ERR(ctx->fh.m2m_ctx);
> +
> +		v4l2_fh_exit(&ctx->fh);
> +		kfree(ctx);
> +		goto open_unlock;
> +	}
> +
> +	v4l2_fh_add(&ctx->fh);
> +
> +	dprintk(dev, 1, "Created instance: %p, m2m_ctx: %p\n",
> +		ctx, ctx->fh.m2m_ctx);
> +
> +open_unlock:
> +	mutex_unlock(&dev->dev_mutex);
> +	return rc;
> +}
> +
> +static int audm2m_release(struct file *file)
> +{
> +	struct audm2m_dev *dev = video_drvdata(file);
> +	struct audm2m_ctx *ctx = file2ctx(file);
> +
> +	dprintk(dev, 1, "Releasing instance %p\n", ctx);
> +
> +	v4l2_fh_del(&ctx->fh);
> +	v4l2_fh_exit(&ctx->fh);
> +	mutex_lock(&dev->dev_mutex);
> +	v4l2_m2m_ctx_release(ctx->fh.m2m_ctx);
> +	mutex_unlock(&dev->dev_mutex);
> +	kfree(ctx);
> +
> +	return 0;
> +}
> +
> +static void audm2m_device_release(struct video_device *vdev)
> +{
> +	struct audm2m_dev *dev = container_of(vdev, struct audm2m_dev, vfd);
> +
> +	v4l2_device_unregister(&dev->v4l2_dev);
> +	v4l2_m2m_release(dev->m2m_dev);
> +
> +	kfree(dev);
> +}
> +
> +static const struct v4l2_file_operations audm2m_fops = {
> +	.owner		= THIS_MODULE,
> +	.open		= audm2m_open,
> +	.release	= audm2m_release,
> +	.poll		= v4l2_m2m_fop_poll,
> +	.unlocked_ioctl	= video_ioctl2,
> +	.mmap		= v4l2_m2m_fop_mmap,
> +};
> +
> +static const struct video_device audm2m_videodev = {
> +	.name		= MEM2MEM_NAME,
> +	.vfl_dir	= VFL_DIR_M2M,
> +	.fops		= &audm2m_fops,
> +	.ioctl_ops	= &audm2m_ioctl_ops,
> +	.minor		= -1,
> +	.release	= audm2m_device_release,
> +	.device_caps	= V4L2_CAP_AUDIO_M2M | V4L2_CAP_STREAMING,
> +};
> +
> +static const struct v4l2_m2m_ops m2m_ops = {
> +	.device_run	= device_run,
> +};
> +
> +static int audm2m_probe(struct platform_device *pdev)
> +{
> +	struct audm2m_dev *dev;
> +	struct video_device *vfd;
> +	int ret;
> +
> +	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
> +	if (!dev)
> +		return -ENOMEM;
> +
> +	ret = v4l2_device_register(&pdev->dev, &dev->v4l2_dev);
> +	if (ret)
> +		goto error_free;
> +
> +	mutex_init(&dev->dev_mutex);
> +
> +	dev->vfd = audm2m_videodev;
> +	vfd = &dev->vfd;
> +	vfd->lock = &dev->dev_mutex;
> +	vfd->v4l2_dev = &dev->v4l2_dev;
> +
> +	video_set_drvdata(vfd, dev);
> +	platform_set_drvdata(pdev, dev);
> +
> +	dev->m2m_dev = v4l2_m2m_init(&m2m_ops);
> +	if (IS_ERR(dev->m2m_dev)) {
> +		v4l2_err(&dev->v4l2_dev, "Failed to init mem2mem device\n");
> +		ret = PTR_ERR(dev->m2m_dev);
> +		dev->m2m_dev = NULL;
> +		goto error_dev;
> +	}
> +
> +	ret = video_register_device(vfd, VFL_TYPE_AUDIO, 0);
> +	if (ret) {
> +		v4l2_err(&dev->v4l2_dev, "Failed to register video device\n");
> +		goto error_m2m;
> +	}
> +
> +	v4l2_info(&dev->v4l2_dev,
> +		  "Device registered as /dev/v4l-audio%d\n", vfd->num);
> +
> +	return 0;
> +
> +error_m2m:
> +	v4l2_m2m_release(dev->m2m_dev);
> +error_dev:
> +	v4l2_device_unregister(&dev->v4l2_dev);
> +error_free:
> +	kfree(dev);
> +
> +	return ret;
> +}
> +
> +static void audm2m_remove(struct platform_device *pdev)
> +{
> +	struct audm2m_dev *dev = platform_get_drvdata(pdev);
> +
> +	v4l2_info(&dev->v4l2_dev, "Removing " MEM2MEM_NAME);
> +
> +	video_unregister_device(&dev->vfd);
> +}
> +
> +static struct platform_driver audm2m_pdrv = {
> +	.probe		= audm2m_probe,
> +	.remove_new	= audm2m_remove,
> +	.driver		= {
> +		.name	= MEM2MEM_NAME,
> +	},
> +};
> +
> +static void __exit audm2m_exit(void)
> +{
> +	platform_driver_unregister(&audm2m_pdrv);
> +	platform_device_unregister(&audm2m_pdev);
> +}
> +
> +static int __init audm2m_init(void)
> +{
> +	int ret;
> +
> +	ret = platform_device_register(&audm2m_pdev);
> +	if (ret)
> +		return ret;
> +
> +	ret = platform_driver_register(&audm2m_pdrv);
> +	if (ret)
> +		platform_device_unregister(&audm2m_pdev);
> +
> +	return ret;
> +}
> +
> +module_init(audm2m_init);
> +module_exit(audm2m_exit);