On Sunday, November 21, 2010 22:45:48 Laurent Pinchart wrote:
> Hi Hans,
>
> Thanks for the comment.
>
> On Sunday 21 November 2010 22:18:41 Hans Verkuil wrote:
> > On Sunday, November 21, 2010 21:32:49 Laurent Pinchart wrote:
> > > uvc_find_control() must be called with the controls mutex locked. Fix
> > > uvc_query_v4l2_menu() accordingly.
> > >
> > > Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> > > ---
> > >
> > > drivers/media/video/uvc/uvc_ctrl.c | 48
> > > +++++++++++++++++++++++++++++++++++- drivers/media/video/uvc/uvc_v4l2.c
> > > | 36 +-------------------------- drivers/media/video/uvc/uvcvideo.h |
> > > 4 +-
> > > 3 files changed, 50 insertions(+), 38 deletions(-)
> > >
> > > diff --git a/drivers/media/video/uvc/uvc_ctrl.c
> > > b/drivers/media/video/uvc/uvc_ctrl.c index f169f77..59f8a9a 100644
> > > --- a/drivers/media/video/uvc/uvc_ctrl.c
> > > +++ b/drivers/media/video/uvc/uvc_ctrl.c
> > > @@ -785,7 +785,7 @@ static void __uvc_find_control(struct uvc_entity
> > > *entity, __u32 v4l2_id,
> > >
> > > }
> > >
> > > }
> > >
> > > -struct uvc_control *uvc_find_control(struct uvc_video_chain *chain,
> > > +static struct uvc_control *uvc_find_control(struct uvc_video_chain
> > > *chain,
> > >
> > > __u32 v4l2_id, struct uvc_control_mapping **mapping)
> > >
> > > {
> > >
> > > struct uvc_control *ctrl = NULL;
> > >
> > > @@ -944,6 +944,52 @@ done:
> > > return ret;
> > >
> > > }
> > >
> > > +/*
> > > + * Mapping V4L2 controls to UVC controls can be straighforward if done
> > > well. + * Most of the UVC controls exist in V4L2, and can be mapped
> > > directly. Some + * must be grouped (for instance the Red Balance, Blue
> > > Balance and Do White + * Balance V4L2 controls use the White Balance
> > > Component UVC control) or + * otherwise translated. The approach we take
> > > here is to use a translation + * table for the controls that can be
> > > mapped directly, and handle the others + * manually.
> > > + */
> > > +int uvc_query_v4l2_menu(struct uvc_video_chain *chain,
> > > + struct v4l2_querymenu *query_menu)
> > > +{
> > > + struct uvc_menu_info *menu_info;
> > > + struct uvc_control_mapping *mapping;
> > > + struct uvc_control *ctrl;
> > > + u32 index = query_menu->index;
> > > + u32 id = query_menu->id;
> > > + int ret;
> > > +
> > > + memset(query_menu, 0, sizeof(*query_menu));
> > > + query_menu->id = id;
> > > + query_menu->index = index;
> > > +
> > > + ret = mutex_lock_interruptible(&chain->ctrl_mutex);
> > > + if (ret < 0)
> > > + return -ERESTARTSYS;
> >
> > Just return 'ret' here (which is -EINTR).
>
> Hmmm... The uvcvideo driver uses -ERESTARTSYS extensively. What's the
> rationale behind using -EINTR instead ? Allowing users to interrupt the ioctl
> with ctrl-C ?
> If so, I wonder if it's worth it in this case, as the controls
> mutex will not be locked by another thread for an extensive period of time
> anyway.
I don't think it is worth it here. It's perfectly fine to switch to mutex_lock.
>
> ERESTARTSYS is meant to be used to deliver signals to application right away
> and then restart the system call. With EINTR applications would see an error
> in response to a VIDIOC_QUERYMENU call if SIGALRM arrives at the same time. I
> don't think that's something we want.
Good point. I never realized that. I will have to modify my patch series for
that. BTW, a quick scan in the kernel sources once again shows random behavior
regarding EINTR vs ERESTARTSYS.
Regards,
Hans
--
Hans Verkuil - video4linux developer - sponsored by Cisco
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