media: camss: Add files which handle the video device nodes

These files handle the video device nodes of the camss driver.
Signed-off-by: Todor Tomov <todor.tomov@linaro.org>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/platform/qcom/camss-8x16/camss-video.c

+/*
+ * camss-video.c
+ *
+ * Qualcomm MSM Camera Subsystem - V4L2 device node
+ *
+ * Copyright (c) 2013-2015, The Linux Foundation. All rights reserved.
+ * Copyright (C) 2015-2017 Linaro Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+#include <linux/slab.h>
+#include <media/media-entity.h>
+#include <media/v4l2-dev.h>
+#include <media/v4l2-device.h>
+#include <media/v4l2-ioctl.h>
+#include <media/v4l2-mc.h>
+#include <media/videobuf-core.h>
+#include <media/videobuf2-dma-sg.h>
+
+#include "camss-video.h"
+#include "camss.h"
+
+/*
+ * struct camss_format_info - ISP media bus format information
+ * @code: V4L2 media bus format code
+ * @pixelformat: V4L2 pixel format FCC identifier
+ * @bpp: Bits per pixel when stored in memory
+ */
+static const struct camss_format_info {
+	u32 code;
+	u32 pixelformat;
+	unsigned int bpp;
+} formats[] = {
+	{ MEDIA_BUS_FMT_UYVY8_2X8, V4L2_PIX_FMT_UYVY, 16 },
+	{ MEDIA_BUS_FMT_VYUY8_2X8, V4L2_PIX_FMT_VYUY, 16 },
+	{ MEDIA_BUS_FMT_YUYV8_2X8, V4L2_PIX_FMT_YUYV, 16 },
+	{ MEDIA_BUS_FMT_YVYU8_2X8, V4L2_PIX_FMT_YVYU, 16 },
+	{ MEDIA_BUS_FMT_SBGGR8_1X8, V4L2_PIX_FMT_SBGGR8, 8 },
+	{ MEDIA_BUS_FMT_SGBRG8_1X8, V4L2_PIX_FMT_SGBRG8, 8 },
+	{ MEDIA_BUS_FMT_SGRBG8_1X8, V4L2_PIX_FMT_SGRBG8, 8 },
+	{ MEDIA_BUS_FMT_SRGGB8_1X8, V4L2_PIX_FMT_SRGGB8, 8 },
+	{ MEDIA_BUS_FMT_SBGGR10_1X10, V4L2_PIX_FMT_SBGGR10P, 10 },
+	{ MEDIA_BUS_FMT_SGBRG10_1X10, V4L2_PIX_FMT_SGBRG10P, 10 },
+	{ MEDIA_BUS_FMT_SGRBG10_1X10, V4L2_PIX_FMT_SGRBG10P, 10 },
+	{ MEDIA_BUS_FMT_SRGGB10_1X10, V4L2_PIX_FMT_SRGGB10P, 10 },
+	{ MEDIA_BUS_FMT_SBGGR12_1X12, V4L2_PIX_FMT_SBGGR12P, 12 },
+	{ MEDIA_BUS_FMT_SGBRG12_1X12, V4L2_PIX_FMT_SGBRG12P, 12 },
+	{ MEDIA_BUS_FMT_SGRBG12_1X12, V4L2_PIX_FMT_SGRBG12P, 12 },
+	{ MEDIA_BUS_FMT_SRGGB12_1X12, V4L2_PIX_FMT_SRGGB12P, 12 }
+};
+
+/* -----------------------------------------------------------------------------
+ * Helper functions
+ */
+
+/*
+ * video_mbus_to_pix_mp - Convert v4l2_mbus_framefmt to v4l2_pix_format_mplane
+ * @mbus: v4l2_mbus_framefmt format (input)
+ * @pix: v4l2_pix_format_mplane format (output)
+ *
+ * Fill the output pix structure with information from the input mbus format.
+ *
+ * Return 0 on success or a negative error code otherwise
+ */
+static unsigned int video_mbus_to_pix_mp(const struct v4l2_mbus_framefmt *mbus,
+					 struct v4l2_pix_format_mplane *pix)
+{
+	unsigned int i;
+	u32 bytesperline;
+
+	memset(pix, 0, sizeof(*pix));
+	v4l2_fill_pix_format_mplane(pix, mbus);
+
+	for (i = 0; i < ARRAY_SIZE(formats); ++i) {
+		if (formats[i].code == mbus->code)
+			break;
+	}
+
+	if (WARN_ON(i == ARRAY_SIZE(formats)))
+		return -EINVAL;
+
+	pix->pixelformat = formats[i].pixelformat;
+	pix->num_planes = 1;
+	bytesperline = pix->width * formats[i].bpp / 8;
+	bytesperline = ALIGN(bytesperline, 8);
+	pix->plane_fmt[0].bytesperline = bytesperline;
+	pix->plane_fmt[0].sizeimage = bytesperline * pix->height;
+
+	return 0;
+}
+
+static struct v4l2_subdev *video_remote_subdev(struct camss_video *video,
+					       u32 *pad)
+{
+	struct media_pad *remote;
+
+	remote = media_entity_remote_pad(&video->pad);
+
+	if (!remote || !is_media_entity_v4l2_subdev(remote->entity))
+		return NULL;
+
+	if (pad)
+		*pad = remote->index;
+
+	return media_entity_to_v4l2_subdev(remote->entity);
+}
+
+static int video_get_subdev_format(struct camss_video *video,
+				   struct v4l2_format *format)
+{
+	struct v4l2_subdev_format fmt;
+	struct v4l2_subdev *subdev;
+	u32 pad;
+	int ret;
+
+	subdev = video_remote_subdev(video, &pad);
+	if (subdev == NULL)
+		return -EPIPE;
+
+	fmt.pad = pad;
+	fmt.which = V4L2_SUBDEV_FORMAT_ACTIVE;
+
+	ret = v4l2_subdev_call(subdev, pad, get_fmt, NULL, &fmt);
+	if (ret)
+		return ret;
+
+	format->type = video->type;
+	return video_mbus_to_pix_mp(&fmt.format, &format->fmt.pix_mp);
+}
+
+/* -----------------------------------------------------------------------------
+ * Video queue operations
+ */
+
+static int video_queue_setup(struct vb2_queue *q,
+	unsigned int *num_buffers, unsigned int *num_planes,
+	unsigned int sizes[], struct device *alloc_devs[])
+{
+	struct camss_video *video = vb2_get_drv_priv(q);
+
+	if (*num_planes) {
+		if (*num_planes != 1)
+			return -EINVAL;
+
+		if (sizes[0] < video->active_fmt.fmt.pix_mp.plane_fmt[0].sizeimage)
+			return -EINVAL;
+
+		return 0;
+	}
+
+	*num_planes = 1;
+
+	sizes[0] = video->active_fmt.fmt.pix_mp.plane_fmt[0].sizeimage;
+
+	return 0;
+}
+
+static int video_buf_prepare(struct vb2_buffer *vb)
+{
+	struct vb2_v4l2_buffer *vbuf = to_vb2_v4l2_buffer(vb);
+	struct camss_video *video = vb2_get_drv_priv(vb->vb2_queue);
+	struct camss_buffer *buffer = container_of(vbuf, struct camss_buffer,
+						   vb);
+	struct sg_table *sgt;
+
+	if (video->active_fmt.fmt.pix_mp.plane_fmt[0].sizeimage >
+							vb2_plane_size(vb, 0))
+		return -EINVAL;
+
+	vb2_set_plane_payload(vb, 0,
+			video->active_fmt.fmt.pix_mp.plane_fmt[0].sizeimage);
+
+	sgt = vb2_dma_sg_plane_desc(vb, 0);
+	if (!sgt)
+		return -EFAULT;
+
+	buffer->addr = sg_dma_address(sgt->sgl);
+
+	vbuf->field = V4L2_FIELD_NONE;
+
+	return 0;
+}
+
+static void video_buf_queue(struct vb2_buffer *vb)
+{
+	struct vb2_v4l2_buffer *vbuf = to_vb2_v4l2_buffer(vb);
+	struct camss_video *video = vb2_get_drv_priv(vb->vb2_queue);
+	struct camss_buffer *buffer = container_of(vbuf, struct camss_buffer,
+						   vb);
+
+	video->ops->queue_buffer(video, buffer);
+}
+
+static int video_check_format(struct camss_video *video)
+{
+	struct v4l2_pix_format_mplane *pix = &video->active_fmt.fmt.pix_mp;
+	struct v4l2_format format;
+	struct v4l2_pix_format_mplane *sd_pix = &format.fmt.pix_mp;
+	int ret;
+
+	ret = video_get_subdev_format(video, &format);
+	if (ret < 0)
+		return ret;
+
+	if (pix->pixelformat != sd_pix->pixelformat ||
+	    pix->height != sd_pix->height ||
+	    pix->width != sd_pix->width ||
+	    pix->num_planes != sd_pix->num_planes ||
+	    pix->num_planes != 1 ||
+	    pix->plane_fmt[0].bytesperline != sd_pix->plane_fmt[0].bytesperline ||
+	    pix->plane_fmt[0].sizeimage != sd_pix->plane_fmt[0].sizeimage ||
+	    pix->field != format.fmt.pix_mp.field)
+		return -EPIPE;
+
+	return 0;
+}
+
+static int video_start_streaming(struct vb2_queue *q, unsigned int count)
+{
+	struct camss_video *video = vb2_get_drv_priv(q);
+	struct video_device *vdev = &video->vdev;
+	struct media_entity *entity;
+	struct media_pad *pad;
+	struct v4l2_subdev *subdev;
+	int ret;
+
+	ret = media_pipeline_start(&vdev->entity, &video->pipe);
+	if (ret < 0)
+		return ret;
+
+	ret = video_check_format(video);
+	if (ret < 0)
+		goto error;
+
+	entity = &vdev->entity;
+	while (1) {
+		pad = &entity->pads[0];
+		if (!(pad->flags & MEDIA_PAD_FL_SINK))
+			break;
+
+		pad = media_entity_remote_pad(pad);
+		if (!pad || !is_media_entity_v4l2_subdev(pad->entity))
+			break;
+
+		entity = pad->entity;
+		subdev = media_entity_to_v4l2_subdev(entity);
+
+		ret = v4l2_subdev_call(subdev, video, s_stream, 1);
+		if (ret < 0 && ret != -ENOIOCTLCMD)
+			goto error;
+	}
+
+	return 0;
+
+error:
+	media_pipeline_stop(&vdev->entity);
+
+	video->ops->flush_buffers(video, VB2_BUF_STATE_QUEUED);
+
+	return ret;
+}
+
+static void video_stop_streaming(struct vb2_queue *q)
+{
+	struct camss_video *video = vb2_get_drv_priv(q);
+	struct video_device *vdev = &video->vdev;
+	struct media_entity *entity;
+	struct media_pad *pad;
+	struct v4l2_subdev *subdev;
+	struct v4l2_subdev *subdev_vfe = NULL;
+
+	entity = &vdev->entity;
+	while (1) {
+		pad = &entity->pads[0];
+		if (!(pad->flags & MEDIA_PAD_FL_SINK))
+			break;
+
+		pad = media_entity_remote_pad(pad);
+		if (!pad || !is_media_entity_v4l2_subdev(pad->entity))
+			break;
+
+		entity = pad->entity;
+		subdev = media_entity_to_v4l2_subdev(entity);
+
+		if (strstr(subdev->name, "vfe")) {
+			subdev_vfe = subdev;
+		} else if (strstr(subdev->name, "ispif")) {
+			v4l2_subdev_call(subdev, video, s_stream, 0);
+			v4l2_subdev_call(subdev_vfe, video, s_stream, 0);
+		} else {
+			v4l2_subdev_call(subdev, video, s_stream, 0);
+		}
+	}
+
+	media_pipeline_stop(&vdev->entity);
+
+	video->ops->flush_buffers(video, VB2_BUF_STATE_ERROR);
+}
+
+static const struct vb2_ops msm_video_vb2_q_ops = {
+	.queue_setup     = video_queue_setup,
+	.wait_prepare    = vb2_ops_wait_prepare,
+	.wait_finish     = vb2_ops_wait_finish,
+	.buf_prepare     = video_buf_prepare,
+	.buf_queue       = video_buf_queue,
+	.start_streaming = video_start_streaming,
+	.stop_streaming  = video_stop_streaming,
+};
+
+/* -----------------------------------------------------------------------------
+ * V4L2 ioctls
+ */
+
+static int video_querycap(struct file *file, void *fh,
+			  struct v4l2_capability *cap)
+{
+	struct camss_video *video = video_drvdata(file);
+
+	strlcpy(cap->driver, "qcom-camss", sizeof(cap->driver));
+	strlcpy(cap->card, "Qualcomm Camera Subsystem", sizeof(cap->card));
+	snprintf(cap->bus_info, sizeof(cap->bus_info), "platform:%s",
+		 dev_name(video->camss->dev));
+
+	return 0;
+}
+
+static int video_enum_fmt(struct file *file, void *fh, struct v4l2_fmtdesc *f)
+{
+	struct camss_video *video = video_drvdata(file);
+
+	if (f->type != video->type)
+		return -EINVAL;
+
+	if (f->index >= ARRAY_SIZE(formats))
+		return -EINVAL;
+
+	f->pixelformat = formats[f->index].pixelformat;
+
+	return 0;
+}
+
+static int video_g_fmt(struct file *file, void *fh, struct v4l2_format *f)
+{
+	struct camss_video *video = video_drvdata(file);
+
+	*f = video->active_fmt;
+
+	return 0;
+}
+
+static int __video_try_fmt(struct camss_video *video, struct v4l2_format *f)
+{
+	struct v4l2_pix_format_mplane *pix_mp;
+	u32 width, height;
+	u32 bpl;
+	int j;
+
+	pix_mp = &f->fmt.pix_mp;
+
+	for (j = 0; j < ARRAY_SIZE(formats); j++)
+		if (pix_mp->pixelformat == formats[j].pixelformat)
+			break;
+
+	if (j == ARRAY_SIZE(formats))
+		j = 0; /* default format */
+
+	width = pix_mp->width;
+	height = pix_mp->height;
+
+	memset(pix_mp, 0, sizeof(*pix_mp));
+
+	pix_mp->pixelformat = formats[j].pixelformat;
+	pix_mp->width = clamp_t(u32, width, 1, 8191);
+	pix_mp->height = clamp_t(u32, height, 1, 8191);
+	pix_mp->num_planes = 1;
+	bpl = pix_mp->width * formats[j].bpp / 8;
+	bpl = ALIGN(bpl, 8);
+	pix_mp->plane_fmt[0].bytesperline = bpl;
+	pix_mp->plane_fmt[0].sizeimage = bpl * pix_mp->height;
+
+	pix_mp->field = V4L2_FIELD_NONE;
+	pix_mp->colorspace = V4L2_COLORSPACE_SRGB;
+	pix_mp->flags = 0;
+	pix_mp->ycbcr_enc = V4L2_MAP_YCBCR_ENC_DEFAULT(pix_mp->colorspace);
+	pix_mp->quantization = V4L2_MAP_QUANTIZATION_DEFAULT(true,
+					pix_mp->colorspace, pix_mp->ycbcr_enc);
+	pix_mp->xfer_func = V4L2_MAP_XFER_FUNC_DEFAULT(pix_mp->colorspace);
+
+	return 0;
+}
+
+static int video_try_fmt(struct file *file, void *fh, struct v4l2_format *f)
+{
+	struct camss_video *video = video_drvdata(file);
+
+	return __video_try_fmt(video, f);
+}
+
+static int video_s_fmt(struct file *file, void *fh, struct v4l2_format *f)
+{
+	struct camss_video *video = video_drvdata(file);
+	int ret;
+
+	if (vb2_is_busy(&video->vb2_q))
+		return -EBUSY;
+
+	ret = __video_try_fmt(video, f);
+	if (ret < 0)
+		return ret;
+
+	video->active_fmt = *f;
+
+	return 0;
+}
+
+static int video_enum_input(struct file *file, void *fh,
+			    struct v4l2_input *input)
+{
+	if (input->index > 0)
+		return -EINVAL;
+
+	strlcpy(input->name, "camera", sizeof(input->name));
+	input->type = V4L2_INPUT_TYPE_CAMERA;
+
+	return 0;
+}
+
+static int video_g_input(struct file *file, void *fh, unsigned int *input)
+{
+	*input = 0;
+
+	return 0;
+}
+
+static int video_s_input(struct file *file, void *fh, unsigned int input)
+{
+	return input == 0 ? 0 : -EINVAL;
+}
+
+static const struct v4l2_ioctl_ops msm_vid_ioctl_ops = {
+	.vidioc_querycap		= video_querycap,
+	.vidioc_enum_fmt_vid_cap_mplane	= video_enum_fmt,
+	.vidioc_g_fmt_vid_cap_mplane	= video_g_fmt,
+	.vidioc_s_fmt_vid_cap_mplane	= video_s_fmt,
+	.vidioc_try_fmt_vid_cap_mplane	= video_try_fmt,
+	.vidioc_reqbufs			= vb2_ioctl_reqbufs,
+	.vidioc_querybuf		= vb2_ioctl_querybuf,
+	.vidioc_qbuf			= vb2_ioctl_qbuf,
+	.vidioc_expbuf			= vb2_ioctl_expbuf,
+	.vidioc_dqbuf			= vb2_ioctl_dqbuf,
+	.vidioc_create_bufs		= vb2_ioctl_create_bufs,
+	.vidioc_prepare_buf		= vb2_ioctl_prepare_buf,
+	.vidioc_streamon		= vb2_ioctl_streamon,
+	.vidioc_streamoff		= vb2_ioctl_streamoff,
+	.vidioc_enum_input		= video_enum_input,
+	.vidioc_g_input			= video_g_input,
+	.vidioc_s_input			= video_s_input,
+};
+
+/* -----------------------------------------------------------------------------
+ * V4L2 file operations
+ */
+
+static int video_open(struct file *file)
+{
+	struct video_device *vdev = video_devdata(file);
+	struct camss_video *video = video_drvdata(file);
+	struct v4l2_fh *vfh;
+	int ret;
+
+	mutex_lock(&video->lock);
+
+	vfh = kzalloc(sizeof(*vfh), GFP_KERNEL);
+	if (vfh == NULL) {
+		ret = -ENOMEM;
+		goto error_alloc;
+	}
+
+	v4l2_fh_init(vfh, vdev);
+	v4l2_fh_add(vfh);
+
+	file->private_data = vfh;
+
+	ret = v4l2_pipeline_pm_use(&vdev->entity, 1);
+	if (ret < 0) {
+		dev_err(video->camss->dev, "Failed to power up pipeline: %d\n",
+			ret);
+		goto error_pm_use;
+	}
+
+	mutex_unlock(&video->lock);
+
+	return 0;
+
+error_pm_use:
+	v4l2_fh_release(file);
+
+error_alloc:
+	mutex_unlock(&video->lock);
+
+	return ret;
+}
+
+static int video_release(struct file *file)
+{
+	struct video_device *vdev = video_devdata(file);
+
+	vb2_fop_release(file);
+
+	v4l2_pipeline_pm_use(&vdev->entity, 0);
+
+	file->private_data = NULL;
+
+	return 0;
+}
+
+static const struct v4l2_file_operations msm_vid_fops = {
+	.owner          = THIS_MODULE,
+	.unlocked_ioctl = video_ioctl2,
+	.open           = video_open,
+	.release        = video_release,
+	.poll           = vb2_fop_poll,
+	.mmap		= vb2_fop_mmap,
+	.read		= vb2_fop_read,
+};
+
+/* -----------------------------------------------------------------------------
+ * CAMSS video core
+ */
+
+static void msm_video_release(struct video_device *vdev)
+{
+	struct camss_video *video = video_get_drvdata(vdev);
+
+	media_entity_cleanup(&vdev->entity);
+
+	mutex_destroy(&video->q_lock);
+	mutex_destroy(&video->lock);
+
+	if (atomic_dec_and_test(&video->camss->ref_count))
+		camss_delete(video->camss);
+}
+
+/*
+ * msm_video_init_format - Helper function to initialize format
+ * @video: struct camss_video
+ *
+ * Initialize pad format with default value.
+ *
+ * Return 0 on success or a negative error code otherwise
+ */
+static int msm_video_init_format(struct camss_video *video)
+{
+	int ret;
+	struct v4l2_format format = {
+		.type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE,
+		.fmt.pix_mp = {
+			.width = 1920,
+			.height = 1080,
+			.pixelformat = formats[0].pixelformat,
+		},
+	};
+
+	ret = __video_try_fmt(video, &format);
+	if (ret < 0)
+		return ret;
+
+	video->active_fmt = format;
+
+	return 0;
+}
+
+/*
+ * msm_video_register - Register a video device node
+ * @video: struct camss_video
+ * @v4l2_dev: V4L2 device
+ * @name: name to be used for the video device node
+ *
+ * Initialize and register a video device node to a V4L2 device. Also
+ * initialize the vb2 queue.
+ *
+ * Return 0 on success or a negative error code otherwise
+ */
+
+int msm_video_register(struct camss_video *video, struct v4l2_device *v4l2_dev,
+		       const char *name)
+{
+	struct media_pad *pad = &video->pad;
+	struct video_device *vdev;
+	struct vb2_queue *q;
+	int ret;
+
+	vdev = &video->vdev;
+
+	mutex_init(&video->q_lock);
+
+	q = &video->vb2_q;
+	q->drv_priv = video;
+	q->mem_ops = &vb2_dma_sg_memops;
+	q->ops = &msm_video_vb2_q_ops;
+	q->type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;
+	q->io_modes = VB2_DMABUF | VB2_MMAP | VB2_READ;
+	q->timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC;
+	q->buf_struct_size = sizeof(struct camss_buffer);
+	q->dev = video->camss->dev;
+	q->lock = &video->q_lock;
+	ret = vb2_queue_init(q);
+	if (ret < 0) {
+		dev_err(v4l2_dev->dev, "Failed to init vb2 queue: %d\n", ret);
+		goto error_vb2_init;
+	}
+
+	pad->flags = MEDIA_PAD_FL_SINK;
+	ret = media_entity_pads_init(&vdev->entity, 1, pad);
+	if (ret < 0) {
+		dev_err(v4l2_dev->dev, "Failed to init video entity: %d\n",
+			ret);
+		goto error_media_init;
+	}
+
+	mutex_init(&video->lock);
+
+	ret = msm_video_init_format(video);
+	if (ret < 0) {
+		dev_err(v4l2_dev->dev, "Failed to init format: %d\n", ret);
+		goto error_video_register;
+	}
+
+	vdev->fops = &msm_vid_fops;
+	vdev->device_caps = V4L2_CAP_VIDEO_CAPTURE_MPLANE | V4L2_CAP_STREAMING |
+							V4L2_CAP_READWRITE;
+	vdev->ioctl_ops = &msm_vid_ioctl_ops;
+	vdev->release = msm_video_release;
+	vdev->v4l2_dev = v4l2_dev;
+	vdev->vfl_dir = VFL_DIR_RX;
+	vdev->queue = &video->vb2_q;
+	vdev->lock = &video->lock;
+	strlcpy(vdev->name, name, sizeof(vdev->name));
+
+	ret = video_register_device(vdev, VFL_TYPE_GRABBER, -1);
+	if (ret < 0) {
+		dev_err(v4l2_dev->dev, "Failed to register video device: %d\n",
+			ret);
+		goto error_video_register;
+	}
+
+	video_set_drvdata(vdev, video);
+	atomic_inc(&video->camss->ref_count);
+
+	return 0;
+
+error_video_register:
+	media_entity_cleanup(&vdev->entity);
+	mutex_destroy(&video->lock);
+error_media_init:
+	vb2_queue_release(&video->vb2_q);
+error_vb2_init:
+	mutex_destroy(&video->q_lock);
+
+	return ret;
+}
+
+void msm_video_stop_streaming(struct camss_video *video)
+{
+	if (vb2_is_streaming(&video->vb2_q))
+		vb2_queue_release(&video->vb2_q);
+}
+
+void msm_video_unregister(struct camss_video *video)
+{
+	atomic_inc(&video->camss->ref_count);
+	video_unregister_device(&video->vdev);
+	atomic_dec(&video->camss->ref_count);
+}

drivers/media/platform/qcom/camss-8x16/camss-video.h

+/*
+ * camss-video.h
+ *
+ * Qualcomm MSM Camera Subsystem - V4L2 device node
+ *
+ * Copyright (c) 2013-2015, The Linux Foundation. All rights reserved.
+ * Copyright (C) 2015-2017 Linaro Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+#ifndef QC_MSM_CAMSS_VIDEO_H
+#define QC_MSM_CAMSS_VIDEO_H
+
+#include <linux/mutex.h>
+#include <linux/videodev2.h>
+#include <media/media-entity.h>
+#include <media/v4l2-dev.h>
+#include <media/v4l2-device.h>
+#include <media/v4l2-fh.h>
+#include <media/v4l2-mediabus.h>
+#include <media/videobuf2-v4l2.h>
+
+struct camss_buffer {
+	struct vb2_v4l2_buffer vb;
+	dma_addr_t addr;
+	struct list_head queue;
+};
+
+struct camss_video;
+
+struct camss_video_ops {
+	int (*queue_buffer)(struct camss_video *vid, struct camss_buffer *buf);
+	int (*flush_buffers)(struct camss_video *vid,
+			     enum vb2_buffer_state state);
+};
+
+struct camss_video {
+	struct camss *camss;
+	struct vb2_queue vb2_q;
+	struct video_device vdev;
+	struct media_pad pad;
+	struct v4l2_format active_fmt;
+	enum v4l2_buf_type type;
+	struct media_pipeline pipe;
+	const struct camss_video_ops *ops;
+	struct mutex lock;
+	struct mutex q_lock;
+};
+
+void msm_video_stop_streaming(struct camss_video *video);
+
+int msm_video_register(struct camss_video *video, struct v4l2_device *v4l2_dev,
+		       const char *name);
+
+void msm_video_unregister(struct camss_video *video);
+
+#endif /* QC_MSM_CAMSS_VIDEO_H */