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Date: Fri, 19 Mar 2021 10:10:03 +0100
From: Hans Verkuil <hverkuil-cisco@...all.nl>
To: Ricardo Ribalda <ribalda@...omium.org>,
Laurent Pinchart <laurent.pinchart@...asonboard.com>,
Mauro Carvalho Chehab <mchehab@...nel.org>,
Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
tfiga@...omium.org
Subject: Re: [PATCH v7 13/17] media: uvcvideo: Return -EACCES to inactive
controls
On 18/03/2021 21:29, Ricardo Ribalda wrote:
> If a control is inactive return -EACCES to let the userspace know that
> the value will not be applied automatically when the control is active
> again.
>
> Reviewed-by: Hans Verkuil <hverkuil-cisco@...all.nl>
> Suggested-by: Hans Verkuil <hverkuil-cisco@...all.nl>
> Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
> ---
> drivers/media/usb/uvc/uvc_ctrl.c | 68 ++++++++++++++++++++++----------
> drivers/media/usb/uvc/uvc_v4l2.c | 11 +++++-
> drivers/media/usb/uvc/uvcvideo.h | 2 +-
> 3 files changed, 58 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> index 24fd5afc4e4f..1ec8333811bc 100644
> --- a/drivers/media/usb/uvc/uvc_ctrl.c
> +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> @@ -1046,8 +1046,33 @@ static int uvc_query_v4l2_class(struct uvc_video_chain *chain, u32 req_id,
> return 0;
> }
>
> +static bool uvc_ctrl_is_inactive(struct uvc_video_chain *chain,
> + struct uvc_control *ctrl,
> + struct uvc_control_mapping *mapping)
> +{
> + struct uvc_control_mapping *master_map = NULL;
> + struct uvc_control *master_ctrl = NULL;
> + s32 val;
> + int ret;
> +
> + if (!mapping->master_id)
> + return false;
> +
> + __uvc_find_control(ctrl->entity, mapping->master_id, &master_map,
> + &master_ctrl, 0);
> +
> + if (!master_ctrl || !(master_ctrl->info.flags & UVC_CTRL_FLAG_GET_CUR))
> + return false;
> +
> + ret = __uvc_ctrl_get(chain, master_ctrl, master_map, &val);
> + if (ret < 0 || val == mapping->master_manual)
> + return false;
> +
> + return true;
> +}
This doesn't work. The problem is that you need to test the new value for the
master control against master_manual, and you are testing against the old value.
So for my uvc camera I have this situation after boot:
auto_exposure 0x009a0901 (menu) : min=0 max=3 default=3 value=3 (Aperture Priority Mode)
1: Manual Mode
3: Aperture Priority Mode
exposure_time_absolute 0x009a0902 (int) : min=3 max=2047 step=1 default=250 value=250 flags=inactive
But trying to change both auto_exposure to manual AND set the new exposure_time_absolute
will fail:
$ v4l2-ctl -c auto_exposure=1,exposure_time_absolute=251
VIDIOC_S_EXT_CTRLS: failed: Permission denied
Error setting controls: Permission denied
This works though with the uvc driver as is currently in the kernel.
Unfortunately, this is not something that is explicitly tested in v4l2-compliance.
Regards,
Hans
> +
> int uvc_ctrl_is_accessible(struct uvc_video_chain *chain, u32 v4l2_id,
> - bool read)
> + unsigned long ioctl)
> {
> struct uvc_control_mapping *mapping;
> struct uvc_control *ctrl;
> @@ -1059,11 +1084,26 @@ int uvc_ctrl_is_accessible(struct uvc_video_chain *chain, u32 v4l2_id,
> if (!ctrl)
> return -EINVAL;
>
> - if (!(ctrl->info.flags & UVC_CTRL_FLAG_GET_CUR) && read)
> - return -EACCES;
> -
> - if (!(ctrl->info.flags & UVC_CTRL_FLAG_SET_CUR) && !read)
> - return -EACCES;
> + switch (ioctl) {
> + case VIDIOC_G_CTRL:
> + case VIDIOC_G_EXT_CTRLS:
> + if (!(ctrl->info.flags & UVC_CTRL_FLAG_GET_CUR))
> + return -EACCES;
> + break;
> + case VIDIOC_S_EXT_CTRLS:
> + case VIDIOC_S_CTRL:
> + if (!(ctrl->info.flags & UVC_CTRL_FLAG_SET_CUR))
> + return -EACCES;
> + if (uvc_ctrl_is_inactive(chain, ctrl, mapping))
> + return -EACCES;
> + break;
> + case VIDIOC_TRY_EXT_CTRLS:
> + if (!(ctrl->info.flags & UVC_CTRL_FLAG_SET_CUR))
> + return -EACCES;
> + break;
> + default:
> + return -EINVAL;
> + }
>
> return 0;
> }
> @@ -1087,8 +1127,6 @@ static int __uvc_query_v4l2_ctrl(struct uvc_video_chain *chain,
> struct uvc_control_mapping *mapping,
> struct v4l2_queryctrl *v4l2_ctrl)
> {
> - struct uvc_control_mapping *master_map = NULL;
> - struct uvc_control *master_ctrl = NULL;
> const struct uvc_menu_info *menu;
> unsigned int i;
>
> @@ -1104,18 +1142,8 @@ static int __uvc_query_v4l2_ctrl(struct uvc_video_chain *chain,
> if (!(ctrl->info.flags & UVC_CTRL_FLAG_SET_CUR))
> v4l2_ctrl->flags |= V4L2_CTRL_FLAG_READ_ONLY;
>
> - if (mapping->master_id)
> - __uvc_find_control(ctrl->entity, mapping->master_id,
> - &master_map, &master_ctrl, 0);
> - if (master_ctrl && (master_ctrl->info.flags & UVC_CTRL_FLAG_GET_CUR)) {
> - s32 val;
> - int ret = __uvc_ctrl_get(chain, master_ctrl, master_map, &val);
> - if (ret < 0)
> - return ret;
> -
> - if (val != mapping->master_manual)
> - v4l2_ctrl->flags |= V4L2_CTRL_FLAG_INACTIVE;
> - }
> + if (uvc_ctrl_is_inactive(chain, ctrl, mapping))
> + v4l2_ctrl->flags |= V4L2_CTRL_FLAG_INACTIVE;
>
> if (!ctrl->cached) {
> int ret = uvc_ctrl_populate_cache(chain, ctrl);
> diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
> index fbb99f3c2fb4..ddebdeb5a81b 100644
> --- a/drivers/media/usb/uvc/uvc_v4l2.c
> +++ b/drivers/media/usb/uvc/uvc_v4l2.c
> @@ -999,6 +999,10 @@ static int uvc_ioctl_g_ctrl(struct file *file, void *fh,
> struct v4l2_ext_control xctrl;
> int ret;
>
> + ret = uvc_ctrl_is_accessible(chain, ctrl->id, VIDIOC_G_CTRL);
> + if (ret)
> + return ret;
> +
> memset(&xctrl, 0, sizeof(xctrl));
> xctrl.id = ctrl->id;
>
> @@ -1023,6 +1027,10 @@ static int uvc_ioctl_s_ctrl(struct file *file, void *fh,
> struct v4l2_ext_control xctrl;
> int ret;
>
> + ret = uvc_ctrl_is_accessible(chain, ctrl->id, VIDIOC_S_CTRL);
> + if (ret)
> + return ret;
> +
> memset(&xctrl, 0, sizeof(xctrl));
> xctrl.id = ctrl->id;
> xctrl.value = ctrl->value;
> @@ -1054,8 +1062,7 @@ static int uvc_ctrl_check_access(struct uvc_video_chain *chain,
> int ret = 0;
>
> for (i = 0; i < ctrls->count; ++ctrl, ++i) {
> - ret = uvc_ctrl_is_accessible(chain, ctrl->id,
> - ioctl == VIDIOC_G_EXT_CTRLS);
> + ret = uvc_ctrl_is_accessible(chain, ctrl->id, ioctl);
> if (ret)
> break;
> }
> diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
> index 9471c342a310..a93aeedb5499 100644
> --- a/drivers/media/usb/uvc/uvcvideo.h
> +++ b/drivers/media/usb/uvc/uvcvideo.h
> @@ -903,7 +903,7 @@ static inline int uvc_ctrl_rollback(struct uvc_fh *handle)
> int uvc_ctrl_get(struct uvc_video_chain *chain, struct v4l2_ext_control *xctrl);
> int uvc_ctrl_set(struct uvc_fh *handle, struct v4l2_ext_control *xctrl);
> int uvc_ctrl_is_accessible(struct uvc_video_chain *chain, u32 v4l2_id,
> - bool read);
> + unsigned long ioctl);
>
> int uvc_xu_ctrl_query(struct uvc_video_chain *chain,
> struct uvc_xu_control_query *xqry);
>
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