[PATCH v3, 0/2] This patchset add read-only(Ro) request for capture queue

[PATCH v3, 0/2] This patchset add read-only(Ro) request for capture queue

[Yunfei Dong]

Hello,

User driver need to get HDR10+ information for each capture buffer;
For some encoder cases, user driver need to get encoded message for
each frame. So add support read-only(Ro) request for capture queue.

There is no upstream driver to use this feature at now, but we are
developing internal driver to use it. If it is ready, we will try to
upstream vdec/venc driver based on this feature.

==============
Introduction
==============

Ro request mean that user driver just can get ext ctrls, set ext ctrls
is not not allowed. Ro Request also can be used in output queue.

Add param ro_requests in struct v4l2_ctrl_handler mean that all CID ctrls
belong to this ctrl handler is read only. Add param ro_ctrl_handler in
struct v4l2_fh used for Ro request.

Add param supports_ro_requests in struct vb2_queue present that capture or
output queue use Ro request.

When set/get ext ctrls, will check whether current CID ctrls is ro ctrls
or not using function v4l2_check_ro_ext_ctrls().

================
Changes in v3
================
-change cover-letter message
-change commit message for patch 02/02
-add sanity check in vb2_core_queue_init()

Yunfei Dong (2):
  media: v4l UAPI: add V4L2_BUF_CAP_SUPPORTS_RO_REQUESTS
  media: v4l: Add Ro request api for capture queue

 .../media/v4l/vidioc-reqbufs.rst              |   4 +
 .../media/common/videobuf2/videobuf2-core.c   |   3 +
 .../media/common/videobuf2/videobuf2-v4l2.c   |   7 ++
 drivers/media/mc/mc-request.c                 |  10 +-
 drivers/media/v4l2-core/v4l2-ctrls.c          | 107 +++++++++++++++---
 drivers/media/v4l2-core/v4l2-ioctl.c          |  22 ++++
 drivers/media/v4l2-core/v4l2-mem2mem.c        |  19 ++--
 include/media/v4l2-ctrls.h                    |  22 +++-
 include/media/v4l2-fh.h                       |   2 +
 include/media/videobuf2-core.h                |   2 +
 include/uapi/linux/videodev2.h                |   1 +
 11 files changed, 161 insertions(+), 38 deletions(-)

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[PATCH v3, 1/2] media: v4l UAPI: add V4L2_BUF_CAP_SUPPORTS_RO_REQUESTS

[Yunfei Dong]

This patch adds support for the V4L2_BUF_CAP_SUPPORTS_RO_REQUESTS
flag. This flag is used for Read-only(Ro) Request.

Signed-off-by: Yunfei Dong <yunfei.dong@mediatek.com>
---
 Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
index b6d52083707b..7c7451773b8e 100644
--- a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
+++ b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
@@ -126,6 +126,7 @@ aborting or finishing any DMA in progress, an implicit
 .. _V4L2-BUF-CAP-SUPPORTS-REQUESTS:
 .. _V4L2-BUF-CAP-SUPPORTS-ORPHANED-BUFS:
 .. _V4L2-BUF-CAP-SUPPORTS-M2M-HOLD-CAPTURE-BUF:
+.. _V4L2-BUF-CAP-SUPPORTS-RO-REQUESTS:
 
 .. cssclass:: longtable
 
@@ -156,6 +157,9 @@ aborting or finishing any DMA in progress, an implicit
       - Only valid for stateless decoders. If set, then userspace can set the
         ``V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF`` flag to hold off on returning the
 	capture buffer until the OUTPUT timestamp changes.
+    * - ``V4L2_BUF_CAP_SUPPORTS_RO_REQUESTS``
+      - 0x00000040
+      - This buffer type supports :ref:`requests <media-request-api>`.
 
 Return Value
 ============
-- 
2.18.0
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Re: [PATCH v3,1/2] media: v4l UAPI: add V4L2_BUF_CAP_SUPPORTS_RO_REQUESTS

[Hans Verkuil]

On 01/07/2020 11:35, Yunfei Dong wrote:
> This patch adds support for the V4L2_BUF_CAP_SUPPORTS_RO_REQUESTS
> flag. This flag is used for Read-only(Ro) Request.
> 
> Signed-off-by: Yunfei Dong <yunfei.dong@mediatek.com>
> ---
>  Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
> index b6d52083707b..7c7451773b8e 100644
> --- a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
> +++ b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
> @@ -126,6 +126,7 @@ aborting or finishing any DMA in progress, an implicit
>  .. _V4L2-BUF-CAP-SUPPORTS-REQUESTS:
>  .. _V4L2-BUF-CAP-SUPPORTS-ORPHANED-BUFS:
>  .. _V4L2-BUF-CAP-SUPPORTS-M2M-HOLD-CAPTURE-BUF:
> +.. _V4L2-BUF-CAP-SUPPORTS-RO-REQUESTS:
>  
>  .. cssclass:: longtable
>  
> @@ -156,6 +157,9 @@ aborting or finishing any DMA in progress, an implicit
>        - Only valid for stateless decoders. If set, then userspace can set the
>          ``V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF`` flag to hold off on returning the
>  	capture buffer until the OUTPUT timestamp changes.
> +    * - ``V4L2_BUF_CAP_SUPPORTS_RO_REQUESTS``
> +      - 0x00000040
> +      - This buffer type supports :ref:`requests <media-request-api>`.

This is wrong, it supports *read-only* requests.

Also, Documentation/userspace-api/media/mediactl/request-api.rst should mention
read-only requests: I think a new section "Read-Only Requests" explaining the
purpose and use of such requests would be best. It can be inserted just before
the "Example for a Codec Device" at the end.

Regards,

	Hans

>  
>  Return Value
>  ============
> 


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[PATCH v3,2/2] media: v4l: Add Ro request api for capture queue

[Yunfei Dong]

Add Read-only(Ro) request for capture queue. Ro request mean that
user driver can get ext ctrls, buf set ext ctrls is not allowed.

Add param ro_requests in struct v4l2_ctrl_handler mean that all CID ctrls
belong to this ctrl handler is read only. Add param ro_ctrl_handler in
struct v4l2_fh used for ro request.

Add param supports_ro_requests in struct vb2_queue present that capture or
output queue use ro request.

When set/get ext ctrls, will check whether current CID ctrls is ro ctrls
or not using function v4l2_check_ro_ext_ctrls().

Signed-off-by: Yunfei Dong <yunfei.dong@mediatek.com>
---
 .../media/common/videobuf2/videobuf2-core.c   |   3 +
 .../media/common/videobuf2/videobuf2-v4l2.c   |   7 ++
 drivers/media/mc/mc-request.c                 |  10 +-
 drivers/media/v4l2-core/v4l2-ctrls.c          | 107 +++++++++++++++---
 drivers/media/v4l2-core/v4l2-ioctl.c          |  22 ++++
 drivers/media/v4l2-core/v4l2-mem2mem.c        |  19 ++--
 include/media/v4l2-ctrls.h                    |  22 +++-
 include/media/v4l2-fh.h                       |   2 +
 include/media/videobuf2-core.h                |   2 +
 include/uapi/linux/videodev2.h                |   1 +
 10 files changed, 157 insertions(+), 38 deletions(-)

diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
index 44d65f5be845..230b4909fe35 100644
--- a/drivers/media/common/videobuf2/videobuf2-core.c
+++ b/drivers/media/common/videobuf2/videobuf2-core.c
@@ -2275,6 +2275,9 @@ int vb2_core_queue_init(struct vb2_queue *q)
 	if (WARN_ON(q->requires_requests && !q->supports_requests))
 		return -EINVAL;
 
+	if (WARN_ON(q->supports_ro_requests && !q->supports_requests))
+		return -EINVAL;
+
 	INIT_LIST_HEAD(&q->queued_list);
 	INIT_LIST_HEAD(&q->done_list);
 	spin_lock_init(&q->done_lock);
diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
index eb5d5db96552..91a6f3a0c208 100644
--- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
+++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
@@ -402,6 +402,11 @@ static int vb2_queue_or_prepare_buf(struct vb2_queue *q, struct media_device *md
 			return -EBUSY;
 		}
 		return 0;
+	} else if (!V4L2_TYPE_IS_OUTPUT(q->type)) {
+		if (!q->supports_ro_requests || q->supports_requests) {
+			dprintk(1, "%s: cap queue use ro requests\n", opname);
+			return -EBADR;
+		}
 	} else if (!q->supports_requests) {
 		dprintk(1, "%s: queue does not support requests\n", opname);
 		return -EBADR;
@@ -665,6 +670,8 @@ static void fill_buf_caps(struct vb2_queue *q, u32 *caps)
 #ifdef CONFIG_MEDIA_CONTROLLER_REQUEST_API
 	if (q->supports_requests)
 		*caps |= V4L2_BUF_CAP_SUPPORTS_REQUESTS;
+	if (q->supports_ro_requests)
+		*caps |= V4L2_BUF_CAP_SUPPORTS_RO_REQUESTS;
 #endif
 }
 
diff --git a/drivers/media/mc/mc-request.c b/drivers/media/mc/mc-request.c
index e3fca436c75b..e50ae259c1ff 100644
--- a/drivers/media/mc/mc-request.c
+++ b/drivers/media/mc/mc-request.c
@@ -404,16 +404,12 @@ int media_request_object_bind(struct media_request *req,
 			      struct media_request_object *obj)
 {
 	unsigned long flags;
-	int ret = -EBUSY;
 
 	if (WARN_ON(!ops->release))
 		return -EBADR;
 
 	spin_lock_irqsave(&req->lock, flags);
 
-	if (WARN_ON(req->state != MEDIA_REQUEST_STATE_UPDATING))
-		goto unlock;
-
 	obj->req = req;
 	obj->ops = ops;
 	obj->priv = priv;
@@ -423,11 +419,9 @@ int media_request_object_bind(struct media_request *req,
 	else
 		list_add(&obj->list, &req->objects);
 	req->num_incomplete_objects++;
-	ret = 0;
-
-unlock:
 	spin_unlock_irqrestore(&req->lock, flags);
-	return ret;
+
+	return 0;
 }
 EXPORT_SYMBOL_GPL(media_request_object_bind);
 
diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
index 3f3fbcd60cc6..effc26f733de 100644
--- a/drivers/media/v4l2-core/v4l2-ctrls.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls.c
@@ -3386,22 +3386,6 @@ static const struct media_request_object_ops req_ops = {
 	.release = v4l2_ctrl_request_release,
 };
 
-struct v4l2_ctrl_handler *v4l2_ctrl_request_hdl_find(struct media_request *req,
-					struct v4l2_ctrl_handler *parent)
-{
-	struct media_request_object *obj;
-
-	if (WARN_ON(req->state != MEDIA_REQUEST_STATE_VALIDATING &&
-		    req->state != MEDIA_REQUEST_STATE_QUEUED))
-		return NULL;
-
-	obj = media_request_object_find(req, &req_ops, parent);
-	if (obj)
-		return container_of(obj, struct v4l2_ctrl_handler, req_obj);
-	return NULL;
-}
-EXPORT_SYMBOL_GPL(v4l2_ctrl_request_hdl_find);
-
 struct v4l2_ctrl *
 v4l2_ctrl_request_hdl_ctrl_find(struct v4l2_ctrl_handler *hdl, u32 id)
 {
@@ -3420,6 +3404,10 @@ static int v4l2_ctrl_request_bind(struct media_request *req,
 	ret = v4l2_ctrl_request_clone(hdl, from);
 
 	if (!ret) {
+		if (!hdl->ro_requests &&
+			WARN_ON(req->state != MEDIA_REQUEST_STATE_UPDATING))
+			return -EBUSY;
+
 		ret = media_request_object_bind(req, &req_ops,
 						from, false, &hdl->req_obj);
 		if (!ret)
@@ -3593,6 +3581,62 @@ static int class_check(struct v4l2_ctrl_handler *hdl, u32 which)
 	return find_ref_lock(hdl, which | 1) ? 0 : -EINVAL;
 }
 
+int v4l2_check_ro_ext_ctrls(struct v4l2_ctrl_handler *hdl,
+		   struct video_device *vdev, struct media_device *mdev,
+		   struct v4l2_ext_controls *cs)
+{
+	struct v4l2_ctrl_ref *ref;
+	u32 i;
+
+	if (cs->which == V4L2_CTRL_WHICH_REQUEST_VAL) {
+		if (!mdev || cs->request_fd < 0)
+			return -EINVAL;
+	}
+
+	cs->error_idx = cs->count;
+	cs->which = V4L2_CTRL_ID2WHICH(cs->which);
+
+	if (hdl == NULL)
+		return -EINVAL;
+
+	if (cs->count == 0)
+		return class_check(hdl, cs->which);
+
+	for (i = 0; i < cs->count; i++) {
+		struct v4l2_ext_control *c = &cs->controls[i];
+		u32 id = c->id & V4L2_CTRL_ID_MASK;
+
+		cs->error_idx = i;
+
+		if (cs->which &&
+			cs->which != V4L2_CTRL_WHICH_DEF_VAL &&
+			cs->which != V4L2_CTRL_WHICH_REQUEST_VAL &&
+			V4L2_CTRL_ID2WHICH(id) != cs->which) {
+			dprintk(vdev,
+					"invalid which 0x%x or control id 0x%x\n",
+					cs->which, id);
+			return -EINVAL;
+		}
+
+		/* Old-style private controls are not allowed for
+		 *extended controls
+		 */
+		if (id >= V4L2_CID_PRIVATE_BASE) {
+			dprintk(vdev,
+					"old-style private controls not allowed\n");
+			return -EINVAL;
+		}
+
+		ref = find_ref_lock(hdl, id);
+		if (ref == NULL) {
+			dprintk(vdev, "cannot find control id 0x%x\n", id);
+			return -EINVAL;
+		}
+	}
+	return 0;
+}
+EXPORT_SYMBOL(v4l2_check_ro_ext_ctrls);
+
 /* Get extended controls. Allocates the helpers array if needed. */
 static int v4l2_g_ext_ctrls_common(struct v4l2_ctrl_handler *hdl,
 				   struct v4l2_ext_controls *cs,
@@ -3694,7 +3738,7 @@ v4l2_ctrls_find_req_obj(struct v4l2_ctrl_handler *hdl,
 	obj = media_request_object_find(req, &req_ops, hdl);
 	if (obj)
 		return obj;
-	if (!set)
+	if (!set && !hdl->ro_requests)
 		return ERR_PTR(-ENOENT);
 
 	new_hdl = kzalloc(sizeof(*new_hdl), GFP_KERNEL);
@@ -3702,6 +3746,7 @@ v4l2_ctrls_find_req_obj(struct v4l2_ctrl_handler *hdl,
 		return ERR_PTR(-ENOMEM);
 
 	obj = &new_hdl->req_obj;
+	new_hdl->ro_requests = hdl->ro_requests;
 	ret = v4l2_ctrl_handler_init(new_hdl, (hdl->nr_of_buckets - 1) * 8);
 	if (!ret)
 		ret = v4l2_ctrl_request_bind(req, new_hdl, hdl);
@@ -3763,6 +3808,28 @@ int v4l2_g_ext_ctrls(struct v4l2_ctrl_handler *hdl, struct video_device *vdev,
 }
 EXPORT_SYMBOL(v4l2_g_ext_ctrls);
 
+struct v4l2_ctrl_handler *v4l2_ctrl_request_hdl_find(struct media_request *req,
+					struct v4l2_ctrl_handler *parent)
+{
+	struct media_request_object *obj;
+
+	if (WARN_ON(req->state != MEDIA_REQUEST_STATE_VALIDATING &&
+		    req->state != MEDIA_REQUEST_STATE_QUEUED))
+		return NULL;
+
+	obj = media_request_object_find(req, &req_ops, parent);
+	if (!obj) {
+		if (parent->ro_requests) {
+			obj = v4l2_ctrls_find_req_obj(parent, req, false);
+			if (IS_ERR(obj))
+				return NULL;
+		} else
+			return NULL;
+	}
+	return container_of(obj, struct v4l2_ctrl_handler, req_obj);
+}
+EXPORT_SYMBOL_GPL(v4l2_ctrl_request_hdl_find);
+
 /* Helper function to get a single control */
 static int get_ctrl(struct v4l2_ctrl *ctrl, struct v4l2_ext_control *c)
 {
@@ -4094,6 +4161,12 @@ static int try_set_ext_ctrls(struct v4l2_fh *fh,
 	int ret;
 
 	if (cs->which == V4L2_CTRL_WHICH_REQUEST_VAL) {
+		if (hdl->ro_requests) {
+			dprintk(vdev, "%s: ro requests can`t set ext ctrls\n",
+				video_device_node_name(vdev));
+			return -EINVAL;
+		}
+
 		if (!mdev) {
 			dprintk(vdev, "%s: missing media device\n",
 				video_device_node_name(vdev));
diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
index 2322f08a98be..b9e1058a5067 100644
--- a/drivers/media/v4l2-core/v4l2-ioctl.c
+++ b/drivers/media/v4l2-core/v4l2-ioctl.c
@@ -2270,6 +2270,13 @@ static int v4l_g_ext_ctrls(const struct v4l2_ioctl_ops *ops,
 		test_bit(V4L2_FL_USES_V4L2_FH, &vfd->flags) ? fh : NULL;
 
 	p->error_idx = p->count;
+	if (vfh && vfh->ro_ctrl_handler) {
+		if (!v4l2_check_ro_ext_ctrls(vfh->ro_ctrl_handler, vfd,
+						vfd->v4l2_dev->mdev, p)) {
+			return v4l2_g_ext_ctrls(vfh->ro_ctrl_handler, vfd,
+						vfd->v4l2_dev->mdev, p);
+		}
+	}
 	if (vfh && vfh->ctrl_handler)
 		return v4l2_g_ext_ctrls(vfh->ctrl_handler,
 					vfd, vfd->v4l2_dev->mdev, p);
@@ -2291,6 +2298,14 @@ static int v4l_s_ext_ctrls(const struct v4l2_ioctl_ops *ops,
 		test_bit(V4L2_FL_USES_V4L2_FH, &vfd->flags) ? fh : NULL;
 
 	p->error_idx = p->count;
+	if (vfh && vfh->ro_ctrl_handler) {
+		if (!v4l2_check_ro_ext_ctrls(vfh->ro_ctrl_handler, vfd,
+						vfd->v4l2_dev->mdev, p)) {
+			return v4l2_s_ext_ctrls(vfh, vfh->ro_ctrl_handler, vfd,
+						vfd->v4l2_dev->mdev, p);
+		}
+	}
+
 	if (vfh && vfh->ctrl_handler)
 		return v4l2_s_ext_ctrls(vfh, vfh->ctrl_handler,
 					vfd, vfd->v4l2_dev->mdev, p);
@@ -2312,6 +2327,13 @@ static int v4l_try_ext_ctrls(const struct v4l2_ioctl_ops *ops,
 		test_bit(V4L2_FL_USES_V4L2_FH, &vfd->flags) ? fh : NULL;
 
 	p->error_idx = p->count;
+	if (vfh && vfh->ro_ctrl_handler) {
+		if (!v4l2_check_ro_ext_ctrls(vfh->ro_ctrl_handler, vfd,
+						vfd->v4l2_dev->mdev, p)) {
+			return v4l2_try_ext_ctrls(vfh->ro_ctrl_handler, vfd,
+						vfd->v4l2_dev->mdev, p);
+		}
+	}
 	if (vfh && vfh->ctrl_handler)
 		return v4l2_try_ext_ctrls(vfh->ctrl_handler,
 					  vfd, vfd->v4l2_dev->mdev, p);
diff --git a/drivers/media/v4l2-core/v4l2-mem2mem.c b/drivers/media/v4l2-core/v4l2-mem2mem.c
index 62ac9424c92a..166e94ee18a7 100644
--- a/drivers/media/v4l2-core/v4l2-mem2mem.c
+++ b/drivers/media/v4l2-core/v4l2-mem2mem.c
@@ -712,13 +712,6 @@ int v4l2_m2m_qbuf(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
 	int ret;
 
 	vq = v4l2_m2m_get_vq(m2m_ctx, buf->type);
-	if (!V4L2_TYPE_IS_OUTPUT(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;
@@ -1252,10 +1245,14 @@ void v4l2_m2m_request_queue(struct media_request *req)
 		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);
+			if (V4L2_TYPE_IS_OUTPUT(vb->vb2_queue->type))
+				m2m_ctx_obj = container_of(vb->vb2_queue,
+							struct v4l2_m2m_ctx,
+							out_q_ctx.q);
+			else
+				m2m_ctx_obj = container_of(vb->vb2_queue,
+							struct v4l2_m2m_ctx,
+							cap_q_ctx.q);
 			WARN_ON(m2m_ctx && m2m_ctx_obj != m2m_ctx);
 			m2m_ctx = m2m_ctx_obj;
 		}
diff --git a/include/media/v4l2-ctrls.h b/include/media/v4l2-ctrls.h
index f40e2cbb21d3..5b10c2e8a402 100644
--- a/include/media/v4l2-ctrls.h
+++ b/include/media/v4l2-ctrls.h
@@ -345,6 +345,7 @@ struct v4l2_ctrl_ref {
  * @nr_of_buckets: Total number of buckets in the array.
  * @error:	The error code of the first failed control addition.
  * @request_is_queued: True if the request was queued.
+ * @ro_requests: True if the queue support ro request.
  * @requests:	List to keep track of open control handler request objects.
  *		For the parent control handler (@req_obj.req == NULL) this
  *		is the list header. When the parent control handler is
@@ -368,6 +369,7 @@ struct v4l2_ctrl_handler {
 	u16 nr_of_buckets;
 	int error;
 	bool request_is_queued;
+	bool ro_requests;
 	struct list_head requests;
 	struct list_head requests_queued;
 	struct media_request_object req_obj;
@@ -1261,8 +1263,10 @@ void v4l2_ctrl_request_complete(struct media_request *req,
  * @parent: The parent control handler ('priv' in media_request_object_find())
  *
  * This function finds the control handler in the request. It may return
- * NULL if not found. When done, you must call v4l2_ctrl_request_put_hdl()
- * with the returned handler pointer.
+ * NULL if not found. But for Ro Request, the request object maybe
+ * NULL, need to call v4l2_ctrls_find_req_obj() to check whether the
+ * request has request object. When done, you must call
+ * v4l2_ctrl_request_put_hdl() with the returned handler pointer.
  *
  * If the request is not in state VALIDATING or QUEUED, then this function
  * will always return NULL.
@@ -1454,4 +1458,18 @@ int v4l2_ctrl_subdev_log_status(struct v4l2_subdev *sd);
 int v4l2_ctrl_new_fwnode_properties(struct v4l2_ctrl_handler *hdl,
 				    const struct v4l2_ctrl_ops *ctrl_ops,
 				    const struct v4l2_fwnode_device_properties *p);
+/**
+ * v4l2_check_ro_ext_ctrls - Check whether the ext controls are ro request
+ *
+ * @hdl: pointer to &struct v4l2_ctrl_handler
+ * @vdev: pointer to &struct video_device
+ * @mdev: pointer to &struct media_device
+ * @cs: pointer to &struct v4l2_ext_controls
+ *
+ * If hdl == NULL then they will all return -EINVAL.
+ */
+int v4l2_check_ro_ext_ctrls(struct v4l2_ctrl_handler *hdl,
+			    struct video_device *vdev,
+			    struct media_device *mdev,
+			    struct v4l2_ext_controls *cs);
 #endif
diff --git a/include/media/v4l2-fh.h b/include/media/v4l2-fh.h
index b5b3e00c8e6a..479abef6c910 100644
--- a/include/media/v4l2-fh.h
+++ b/include/media/v4l2-fh.h
@@ -27,6 +27,7 @@ struct v4l2_ctrl_handler;
  * @list: list of file handlers
  * @vdev: pointer to &struct video_device
  * @ctrl_handler: pointer to &struct v4l2_ctrl_handler
+ * @ro_ctrl_handler: pointer to &struct v4l2_ctrl_handler used for ro ctrls
  * @prio: priority of the file handler, as defined by &enum v4l2_priority
  *
  * @wait: event' s wait queue
@@ -43,6 +44,7 @@ struct v4l2_fh {
 	struct list_head	list;
 	struct video_device	*vdev;
 	struct v4l2_ctrl_handler *ctrl_handler;
+	struct v4l2_ctrl_handler *ro_ctrl_handler;
 	enum v4l2_priority	prio;
 
 	/* Events */
diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index f11b96514cf7..dce5c6781be9 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -483,6 +483,7 @@ struct vb2_buf_ops {
  *              has not been called. This is a vb1 idiom that has been adopted
  *              also by vb2.
  * @supports_requests: this queue supports the Request API.
+ * @supports_ro_requests: this queue supports the RO Request API.
  * @requires_requests: this queue requires the Request API. If this is set to 1,
  *		then supports_requests must be set to 1 as well.
  * @uses_qbuf:	qbuf was used directly for this queue. Set to 1 the first
@@ -564,6 +565,7 @@ struct vb2_queue {
 	unsigned			allow_zero_bytesused:1;
 	unsigned		   quirk_poll_must_check_waiting_for_buffers:1;
 	unsigned			supports_requests:1;
+	unsigned			supports_ro_requests:1;
 	unsigned			requires_requests:1;
 	unsigned			uses_qbuf:1;
 	unsigned			uses_requests:1;
diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index c3a1cf1c507f..25793c737eab 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -954,6 +954,7 @@ struct v4l2_requestbuffers {
 #define V4L2_BUF_CAP_SUPPORTS_REQUESTS			(1 << 3)
 #define V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS		(1 << 4)
 #define V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF	(1 << 5)
+#define V4L2_BUF_CAP_SUPPORTS_RO_REQUESTS		(1 << 6)
 
 /**
  * struct v4l2_plane - plane info for multi-planar buffers
-- 
2.18.0
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Re: [PATCH v3,2/2] media: v4l: Add Ro request api for capture queue

[Hans Verkuil]

Hi Yunfei,

On 01/07/2020 11:35, Yunfei Dong wrote:
> Add Read-only(Ro) request for capture queue. Ro request mean that
> user driver can get ext ctrls, buf set ext ctrls is not allowed.
> 
> Add param ro_requests in struct v4l2_ctrl_handler mean that all CID ctrls
> belong to this ctrl handler is read only. Add param ro_ctrl_handler in
> struct v4l2_fh used for ro request.
> 
> Add param supports_ro_requests in struct vb2_queue present that capture or
> output queue use ro request.
> 
> When set/get ext ctrls, will check whether current CID ctrls is ro ctrls
> or not using function v4l2_check_ro_ext_ctrls().

I've been looking at this patch, but I don't like it, esp. the v4l2-ctls changes.

I plan to look into this in more detail next week and see if I can come up
with a better way of doing this.

The core problem from what I can see is not actually RO requests (that's just
a regular request, except userspace can't set controls in the request), but
instead it is that there is some code missing to have a driver add a new control
to an existing request. That's a problem even with 'regular' requests, and this
requires some work.

Hopefully I will have something by the end of next week.

Regards,

	Hans

> 
> Signed-off-by: Yunfei Dong <yunfei.dong@mediatek.com>
> ---
>  .../media/common/videobuf2/videobuf2-core.c   |   3 +
>  .../media/common/videobuf2/videobuf2-v4l2.c   |   7 ++
>  drivers/media/mc/mc-request.c                 |  10 +-
>  drivers/media/v4l2-core/v4l2-ctrls.c          | 107 +++++++++++++++---
>  drivers/media/v4l2-core/v4l2-ioctl.c          |  22 ++++
>  drivers/media/v4l2-core/v4l2-mem2mem.c        |  19 ++--
>  include/media/v4l2-ctrls.h                    |  22 +++-
>  include/media/v4l2-fh.h                       |   2 +
>  include/media/videobuf2-core.h                |   2 +
>  include/uapi/linux/videodev2.h                |   1 +
>  10 files changed, 157 insertions(+), 38 deletions(-)
> 
> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
> index 44d65f5be845..230b4909fe35 100644
> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> @@ -2275,6 +2275,9 @@ int vb2_core_queue_init(struct vb2_queue *q)
>  	if (WARN_ON(q->requires_requests && !q->supports_requests))
>  		return -EINVAL;
>  
> +	if (WARN_ON(q->supports_ro_requests && !q->supports_requests))
> +		return -EINVAL;
> +
>  	INIT_LIST_HEAD(&q->queued_list);
>  	INIT_LIST_HEAD(&q->done_list);
>  	spin_lock_init(&q->done_lock);
> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> index eb5d5db96552..91a6f3a0c208 100644
> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> @@ -402,6 +402,11 @@ static int vb2_queue_or_prepare_buf(struct vb2_queue *q, struct media_device *md
>  			return -EBUSY;
>  		}
>  		return 0;
> +	} else if (!V4L2_TYPE_IS_OUTPUT(q->type)) {
> +		if (!q->supports_ro_requests || q->supports_requests) {
> +			dprintk(1, "%s: cap queue use ro requests\n", opname);
> +			return -EBADR;
> +		}
>  	} else if (!q->supports_requests) {
>  		dprintk(1, "%s: queue does not support requests\n", opname);
>  		return -EBADR;
> @@ -665,6 +670,8 @@ static void fill_buf_caps(struct vb2_queue *q, u32 *caps)
>  #ifdef CONFIG_MEDIA_CONTROLLER_REQUEST_API
>  	if (q->supports_requests)
>  		*caps |= V4L2_BUF_CAP_SUPPORTS_REQUESTS;
> +	if (q->supports_ro_requests)
> +		*caps |= V4L2_BUF_CAP_SUPPORTS_RO_REQUESTS;
>  #endif
>  }
>  
> diff --git a/drivers/media/mc/mc-request.c b/drivers/media/mc/mc-request.c
> index e3fca436c75b..e50ae259c1ff 100644
> --- a/drivers/media/mc/mc-request.c
> +++ b/drivers/media/mc/mc-request.c
> @@ -404,16 +404,12 @@ int media_request_object_bind(struct media_request *req,
>  			      struct media_request_object *obj)
>  {
>  	unsigned long flags;
> -	int ret = -EBUSY;
>  
>  	if (WARN_ON(!ops->release))
>  		return -EBADR;
>  
>  	spin_lock_irqsave(&req->lock, flags);
>  
> -	if (WARN_ON(req->state != MEDIA_REQUEST_STATE_UPDATING))
> -		goto unlock;
> -
>  	obj->req = req;
>  	obj->ops = ops;
>  	obj->priv = priv;
> @@ -423,11 +419,9 @@ int media_request_object_bind(struct media_request *req,
>  	else
>  		list_add(&obj->list, &req->objects);
>  	req->num_incomplete_objects++;
> -	ret = 0;
> -
> -unlock:
>  	spin_unlock_irqrestore(&req->lock, flags);
> -	return ret;
> +
> +	return 0;
>  }
>  EXPORT_SYMBOL_GPL(media_request_object_bind);
>  
> diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
> index 3f3fbcd60cc6..effc26f733de 100644
> --- a/drivers/media/v4l2-core/v4l2-ctrls.c
> +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
> @@ -3386,22 +3386,6 @@ static const struct media_request_object_ops req_ops = {
>  	.release = v4l2_ctrl_request_release,
>  };
>  
> -struct v4l2_ctrl_handler *v4l2_ctrl_request_hdl_find(struct media_request *req,
> -					struct v4l2_ctrl_handler *parent)
> -{
> -	struct media_request_object *obj;
> -
> -	if (WARN_ON(req->state != MEDIA_REQUEST_STATE_VALIDATING &&
> -		    req->state != MEDIA_REQUEST_STATE_QUEUED))
> -		return NULL;
> -
> -	obj = media_request_object_find(req, &req_ops, parent);
> -	if (obj)
> -		return container_of(obj, struct v4l2_ctrl_handler, req_obj);
> -	return NULL;
> -}
> -EXPORT_SYMBOL_GPL(v4l2_ctrl_request_hdl_find);
> -
>  struct v4l2_ctrl *
>  v4l2_ctrl_request_hdl_ctrl_find(struct v4l2_ctrl_handler *hdl, u32 id)
>  {
> @@ -3420,6 +3404,10 @@ static int v4l2_ctrl_request_bind(struct media_request *req,
>  	ret = v4l2_ctrl_request_clone(hdl, from);
>  
>  	if (!ret) {
> +		if (!hdl->ro_requests &&
> +			WARN_ON(req->state != MEDIA_REQUEST_STATE_UPDATING))
> +			return -EBUSY;
> +
>  		ret = media_request_object_bind(req, &req_ops,
>  						from, false, &hdl->req_obj);
>  		if (!ret)
> @@ -3593,6 +3581,62 @@ static int class_check(struct v4l2_ctrl_handler *hdl, u32 which)
>  	return find_ref_lock(hdl, which | 1) ? 0 : -EINVAL;
>  }
>  
> +int v4l2_check_ro_ext_ctrls(struct v4l2_ctrl_handler *hdl,
> +		   struct video_device *vdev, struct media_device *mdev,
> +		   struct v4l2_ext_controls *cs)
> +{
> +	struct v4l2_ctrl_ref *ref;
> +	u32 i;
> +
> +	if (cs->which == V4L2_CTRL_WHICH_REQUEST_VAL) {
> +		if (!mdev || cs->request_fd < 0)
> +			return -EINVAL;
> +	}
> +
> +	cs->error_idx = cs->count;
> +	cs->which = V4L2_CTRL_ID2WHICH(cs->which);
> +
> +	if (hdl == NULL)
> +		return -EINVAL;
> +
> +	if (cs->count == 0)
> +		return class_check(hdl, cs->which);
> +
> +	for (i = 0; i < cs->count; i++) {
> +		struct v4l2_ext_control *c = &cs->controls[i];
> +		u32 id = c->id & V4L2_CTRL_ID_MASK;
> +
> +		cs->error_idx = i;
> +
> +		if (cs->which &&
> +			cs->which != V4L2_CTRL_WHICH_DEF_VAL &&
> +			cs->which != V4L2_CTRL_WHICH_REQUEST_VAL &&
> +			V4L2_CTRL_ID2WHICH(id) != cs->which) {
> +			dprintk(vdev,
> +					"invalid which 0x%x or control id 0x%x\n",
> +					cs->which, id);
> +			return -EINVAL;
> +		}
> +
> +		/* Old-style private controls are not allowed for
> +		 *extended controls
> +		 */
> +		if (id >= V4L2_CID_PRIVATE_BASE) {
> +			dprintk(vdev,
> +					"old-style private controls not allowed\n");
> +			return -EINVAL;
> +		}
> +
> +		ref = find_ref_lock(hdl, id);
> +		if (ref == NULL) {
> +			dprintk(vdev, "cannot find control id 0x%x\n", id);
> +			return -EINVAL;
> +		}
> +	}
> +	return 0;
> +}
> +EXPORT_SYMBOL(v4l2_check_ro_ext_ctrls);
> +
>  /* Get extended controls. Allocates the helpers array if needed. */
>  static int v4l2_g_ext_ctrls_common(struct v4l2_ctrl_handler *hdl,
>  				   struct v4l2_ext_controls *cs,
> @@ -3694,7 +3738,7 @@ v4l2_ctrls_find_req_obj(struct v4l2_ctrl_handler *hdl,
>  	obj = media_request_object_find(req, &req_ops, hdl);
>  	if (obj)
>  		return obj;
> -	if (!set)
> +	if (!set && !hdl->ro_requests)
>  		return ERR_PTR(-ENOENT);
>  
>  	new_hdl = kzalloc(sizeof(*new_hdl), GFP_KERNEL);
> @@ -3702,6 +3746,7 @@ v4l2_ctrls_find_req_obj(struct v4l2_ctrl_handler *hdl,
>  		return ERR_PTR(-ENOMEM);
>  
>  	obj = &new_hdl->req_obj;
> +	new_hdl->ro_requests = hdl->ro_requests;
>  	ret = v4l2_ctrl_handler_init(new_hdl, (hdl->nr_of_buckets - 1) * 8);
>  	if (!ret)
>  		ret = v4l2_ctrl_request_bind(req, new_hdl, hdl);
> @@ -3763,6 +3808,28 @@ int v4l2_g_ext_ctrls(struct v4l2_ctrl_handler *hdl, struct video_device *vdev,
>  }
>  EXPORT_SYMBOL(v4l2_g_ext_ctrls);
>  
> +struct v4l2_ctrl_handler *v4l2_ctrl_request_hdl_find(struct media_request *req,
> +					struct v4l2_ctrl_handler *parent)
> +{
> +	struct media_request_object *obj;
> +
> +	if (WARN_ON(req->state != MEDIA_REQUEST_STATE_VALIDATING &&
> +		    req->state != MEDIA_REQUEST_STATE_QUEUED))
> +		return NULL;
> +
> +	obj = media_request_object_find(req, &req_ops, parent);
> +	if (!obj) {
> +		if (parent->ro_requests) {
> +			obj = v4l2_ctrls_find_req_obj(parent, req, false);
> +			if (IS_ERR(obj))
> +				return NULL;
> +		} else
> +			return NULL;
> +	}
> +	return container_of(obj, struct v4l2_ctrl_handler, req_obj);
> +}
> +EXPORT_SYMBOL_GPL(v4l2_ctrl_request_hdl_find);
> +
>  /* Helper function to get a single control */
>  static int get_ctrl(struct v4l2_ctrl *ctrl, struct v4l2_ext_control *c)
>  {
> @@ -4094,6 +4161,12 @@ static int try_set_ext_ctrls(struct v4l2_fh *fh,
>  	int ret;
>  
>  	if (cs->which == V4L2_CTRL_WHICH_REQUEST_VAL) {
> +		if (hdl->ro_requests) {
> +			dprintk(vdev, "%s: ro requests can`t set ext ctrls\n",
> +				video_device_node_name(vdev));
> +			return -EINVAL;
> +		}
> +
>  		if (!mdev) {
>  			dprintk(vdev, "%s: missing media device\n",
>  				video_device_node_name(vdev));
> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> index 2322f08a98be..b9e1058a5067 100644
> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> @@ -2270,6 +2270,13 @@ static int v4l_g_ext_ctrls(const struct v4l2_ioctl_ops *ops,
>  		test_bit(V4L2_FL_USES_V4L2_FH, &vfd->flags) ? fh : NULL;
>  
>  	p->error_idx = p->count;
> +	if (vfh && vfh->ro_ctrl_handler) {
> +		if (!v4l2_check_ro_ext_ctrls(vfh->ro_ctrl_handler, vfd,
> +						vfd->v4l2_dev->mdev, p)) {
> +			return v4l2_g_ext_ctrls(vfh->ro_ctrl_handler, vfd,
> +						vfd->v4l2_dev->mdev, p);
> +		}
> +	}
>  	if (vfh && vfh->ctrl_handler)
>  		return v4l2_g_ext_ctrls(vfh->ctrl_handler,
>  					vfd, vfd->v4l2_dev->mdev, p);
> @@ -2291,6 +2298,14 @@ static int v4l_s_ext_ctrls(const struct v4l2_ioctl_ops *ops,
>  		test_bit(V4L2_FL_USES_V4L2_FH, &vfd->flags) ? fh : NULL;
>  
>  	p->error_idx = p->count;
> +	if (vfh && vfh->ro_ctrl_handler) {
> +		if (!v4l2_check_ro_ext_ctrls(vfh->ro_ctrl_handler, vfd,
> +						vfd->v4l2_dev->mdev, p)) {
> +			return v4l2_s_ext_ctrls(vfh, vfh->ro_ctrl_handler, vfd,
> +						vfd->v4l2_dev->mdev, p);
> +		}
> +	}
> +
>  	if (vfh && vfh->ctrl_handler)
>  		return v4l2_s_ext_ctrls(vfh, vfh->ctrl_handler,
>  					vfd, vfd->v4l2_dev->mdev, p);
> @@ -2312,6 +2327,13 @@ static int v4l_try_ext_ctrls(const struct v4l2_ioctl_ops *ops,
>  		test_bit(V4L2_FL_USES_V4L2_FH, &vfd->flags) ? fh : NULL;
>  
>  	p->error_idx = p->count;
> +	if (vfh && vfh->ro_ctrl_handler) {
> +		if (!v4l2_check_ro_ext_ctrls(vfh->ro_ctrl_handler, vfd,
> +						vfd->v4l2_dev->mdev, p)) {
> +			return v4l2_try_ext_ctrls(vfh->ro_ctrl_handler, vfd,
> +						vfd->v4l2_dev->mdev, p);
> +		}
> +	}
>  	if (vfh && vfh->ctrl_handler)
>  		return v4l2_try_ext_ctrls(vfh->ctrl_handler,
>  					  vfd, vfd->v4l2_dev->mdev, p);
> diff --git a/drivers/media/v4l2-core/v4l2-mem2mem.c b/drivers/media/v4l2-core/v4l2-mem2mem.c
> index 62ac9424c92a..166e94ee18a7 100644
> --- a/drivers/media/v4l2-core/v4l2-mem2mem.c
> +++ b/drivers/media/v4l2-core/v4l2-mem2mem.c
> @@ -712,13 +712,6 @@ int v4l2_m2m_qbuf(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
>  	int ret;
>  
>  	vq = v4l2_m2m_get_vq(m2m_ctx, buf->type);
> -	if (!V4L2_TYPE_IS_OUTPUT(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;
> @@ -1252,10 +1245,14 @@ void v4l2_m2m_request_queue(struct media_request *req)
>  		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);
> +			if (V4L2_TYPE_IS_OUTPUT(vb->vb2_queue->type))
> +				m2m_ctx_obj = container_of(vb->vb2_queue,
> +							struct v4l2_m2m_ctx,
> +							out_q_ctx.q);
> +			else
> +				m2m_ctx_obj = container_of(vb->vb2_queue,
> +							struct v4l2_m2m_ctx,
> +							cap_q_ctx.q);
>  			WARN_ON(m2m_ctx && m2m_ctx_obj != m2m_ctx);
>  			m2m_ctx = m2m_ctx_obj;
>  		}
> diff --git a/include/media/v4l2-ctrls.h b/include/media/v4l2-ctrls.h
> index f40e2cbb21d3..5b10c2e8a402 100644
> --- a/include/media/v4l2-ctrls.h
> +++ b/include/media/v4l2-ctrls.h
> @@ -345,6 +345,7 @@ struct v4l2_ctrl_ref {
>   * @nr_of_buckets: Total number of buckets in the array.
>   * @error:	The error code of the first failed control addition.
>   * @request_is_queued: True if the request was queued.
> + * @ro_requests: True if the queue support ro request.
>   * @requests:	List to keep track of open control handler request objects.
>   *		For the parent control handler (@req_obj.req == NULL) this
>   *		is the list header. When the parent control handler is
> @@ -368,6 +369,7 @@ struct v4l2_ctrl_handler {
>  	u16 nr_of_buckets;
>  	int error;
>  	bool request_is_queued;
> +	bool ro_requests;
>  	struct list_head requests;
>  	struct list_head requests_queued;
>  	struct media_request_object req_obj;
> @@ -1261,8 +1263,10 @@ void v4l2_ctrl_request_complete(struct media_request *req,
>   * @parent: The parent control handler ('priv' in media_request_object_find())
>   *
>   * This function finds the control handler in the request. It may return
> - * NULL if not found. When done, you must call v4l2_ctrl_request_put_hdl()
> - * with the returned handler pointer.
> + * NULL if not found. But for Ro Request, the request object maybe
> + * NULL, need to call v4l2_ctrls_find_req_obj() to check whether the
> + * request has request object. When done, you must call
> + * v4l2_ctrl_request_put_hdl() with the returned handler pointer.
>   *
>   * If the request is not in state VALIDATING or QUEUED, then this function
>   * will always return NULL.
> @@ -1454,4 +1458,18 @@ int v4l2_ctrl_subdev_log_status(struct v4l2_subdev *sd);
>  int v4l2_ctrl_new_fwnode_properties(struct v4l2_ctrl_handler *hdl,
>  				    const struct v4l2_ctrl_ops *ctrl_ops,
>  				    const struct v4l2_fwnode_device_properties *p);
> +/**
> + * v4l2_check_ro_ext_ctrls - Check whether the ext controls are ro request
> + *
> + * @hdl: pointer to &struct v4l2_ctrl_handler
> + * @vdev: pointer to &struct video_device
> + * @mdev: pointer to &struct media_device
> + * @cs: pointer to &struct v4l2_ext_controls
> + *
> + * If hdl == NULL then they will all return -EINVAL.
> + */
> +int v4l2_check_ro_ext_ctrls(struct v4l2_ctrl_handler *hdl,
> +			    struct video_device *vdev,
> +			    struct media_device *mdev,
> +			    struct v4l2_ext_controls *cs);
>  #endif
> diff --git a/include/media/v4l2-fh.h b/include/media/v4l2-fh.h
> index b5b3e00c8e6a..479abef6c910 100644
> --- a/include/media/v4l2-fh.h
> +++ b/include/media/v4l2-fh.h
> @@ -27,6 +27,7 @@ struct v4l2_ctrl_handler;
>   * @list: list of file handlers
>   * @vdev: pointer to &struct video_device
>   * @ctrl_handler: pointer to &struct v4l2_ctrl_handler
> + * @ro_ctrl_handler: pointer to &struct v4l2_ctrl_handler used for ro ctrls
>   * @prio: priority of the file handler, as defined by &enum v4l2_priority
>   *
>   * @wait: event' s wait queue
> @@ -43,6 +44,7 @@ struct v4l2_fh {
>  	struct list_head	list;
>  	struct video_device	*vdev;
>  	struct v4l2_ctrl_handler *ctrl_handler;
> +	struct v4l2_ctrl_handler *ro_ctrl_handler;
>  	enum v4l2_priority	prio;
>  
>  	/* Events */
> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> index f11b96514cf7..dce5c6781be9 100644
> --- a/include/media/videobuf2-core.h
> +++ b/include/media/videobuf2-core.h
> @@ -483,6 +483,7 @@ struct vb2_buf_ops {
>   *              has not been called. This is a vb1 idiom that has been adopted
>   *              also by vb2.
>   * @supports_requests: this queue supports the Request API.
> + * @supports_ro_requests: this queue supports the RO Request API.
>   * @requires_requests: this queue requires the Request API. If this is set to 1,
>   *		then supports_requests must be set to 1 as well.
>   * @uses_qbuf:	qbuf was used directly for this queue. Set to 1 the first
> @@ -564,6 +565,7 @@ struct vb2_queue {
>  	unsigned			allow_zero_bytesused:1;
>  	unsigned		   quirk_poll_must_check_waiting_for_buffers:1;
>  	unsigned			supports_requests:1;
> +	unsigned			supports_ro_requests:1;
>  	unsigned			requires_requests:1;
>  	unsigned			uses_qbuf:1;
>  	unsigned			uses_requests:1;
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index c3a1cf1c507f..25793c737eab 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -954,6 +954,7 @@ struct v4l2_requestbuffers {
>  #define V4L2_BUF_CAP_SUPPORTS_REQUESTS			(1 << 3)
>  #define V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS		(1 << 4)
>  #define V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF	(1 << 5)
> +#define V4L2_BUF_CAP_SUPPORTS_RO_REQUESTS		(1 << 6)
>  
>  /**
>   * struct v4l2_plane - plane info for multi-planar buffers
> 


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