Hi Hans,
Thanks for the patch.
On Friday 14 September 2012 13:15:34 Hans Verkuil wrote:
> Sometimes platform/bridge drivers need to be notified when a control from
> a subdevice changes value. In order to support this a notify callback was
> added.
>
> Signed-off-by: Hans Verkuil <hans.verk...@cisco.com>
> ---
> Documentation/video4linux/v4l2-controls.txt | 22 ++++++++++++++--------
> drivers/media/v4l2-core/v4l2-ctrls.c | 25 ++++++++++++++++++++++++
> include/media/v4l2-ctrls.h | 25 ++++++++++++++++++++++++
> 3 files changed, 64 insertions(+), 8 deletions(-)
>
> diff --git a/Documentation/video4linux/v4l2-controls.txt
> b/Documentation/video4linux/v4l2-controls.txt index 43da22b..cecaff8 100644
> --- a/Documentation/video4linux/v4l2-controls.txt
> +++ b/Documentation/video4linux/v4l2-controls.txt
> @@ -687,14 +687,20 @@ a control of this type whenever the first control
> belonging to a new control class is added.
>
>
> -Proposals for Extensions
> -========================
> +Adding Notify Callbacks
> +=======================
> +
> +Sometimes the platform or bridge driver needs to be notified when a control
> +from a sub-device driver changes. You can set a notify callback by calling
> +this function:
>
> -Some ideas for future extensions to the spec:
> +void v4l2_ctrl_notify(struct v4l2_ctrl *ctrl,
> + void (*notify)(struct v4l2_ctrl *ctrl, void *priv), void *priv);
>
> -1) Add a V4L2_CTRL_FLAG_HEX to have values shown as hexadecimal instead of
> -decimal. Useful for e.g. video_mute_yuv.
> +Whenever the give control changes value the notify callback will be called
> +with a pointer to the control and the priv pointer that was passed with
> +v4l2_ctrl_notify. Note that the control's handler lock is held when the
> +notify function is called.
>
> -2) It is possible to mark in the controls array which controls have been
> -successfully written and which failed by for example adding a bit to the
> -control ID. Not sure if it is worth the effort, though.
> +There can be only one notify function per control handler. Any attempt
> +to set another notify function will cause a WARN_ON.
> diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c
> b/drivers/media/v4l2-core/v4l2-ctrls.c index f400035..43061e1 100644
> --- a/drivers/media/v4l2-core/v4l2-ctrls.c
> +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
> @@ -1160,6 +1160,8 @@ static void new_to_cur(struct v4l2_fh *fh, struct
> v4l2_ctrl *ctrl, send_event(fh, ctrl,
> (changed ? V4L2_EVENT_CTRL_CH_VALUE : 0) |
> (update_inactive ? V4L2_EVENT_CTRL_CH_FLAGS : 0));
> + if (ctrl->call_notify && changed && ctrl->handler->notify)
> + ctrl->handler->notify(ctrl, ctrl->handler->notify_priv);
> }
> }
>
> @@ -2628,6 +2630,29 @@ int v4l2_ctrl_s_ctrl_int64(struct v4l2_ctrl *ctrl,
> s64 val) }
> EXPORT_SYMBOL(v4l2_ctrl_s_ctrl_int64);
>
> +void v4l2_ctrl_notify(struct v4l2_ctrl *ctrl, v4l2_ctrl_notify_fnc notify,
> void *priv)
> +{
> + if (ctrl == NULL)
> + return;
Isn't the caller supposed not to set ctrl to NULL ? A crash is easier to
notice than a silent failure during development.
> + if (notify == NULL) {
> + ctrl->call_notify = 0;
> + return;
> + }
> + /* Only one notifier is allowed. Should we ever need to support
> + multiple notifiers, then some sort of linked list of notifiers
> + should be implemented. But I don't see any real reason to implement
> + that now. If you think you need multiple notifiers, then contact
> + the linux-media mailinglist. */
> + if (WARN_ON(ctrl->handler->notify &&
> + (ctrl->handler->notify != notify ||
> + ctrl->handler->notify_priv != priv)))
> + return;
I'm not sure whether I like that. It feels a bit hackish. Wouldn't it be
better to register the notifier with the handler explictly just once and then
enable/disable notifications on a per-control basis ?
> + ctrl->handler->notify = notify;
> + ctrl->handler->notify_priv = priv;
> + ctrl->call_notify = 1;
> +}
> +EXPORT_SYMBOL(v4l2_ctrl_notify);
> +
> static int v4l2_ctrl_add_event(struct v4l2_subscribed_event *sev, unsigned
> elems) {
> struct v4l2_ctrl *ctrl = v4l2_ctrl_find(sev->fh->ctrl_handler, sev->id);
> diff --git a/include/media/v4l2-ctrls.h b/include/media/v4l2-ctrls.h
> index 6890f5e..4484fd3 100644
> --- a/include/media/v4l2-ctrls.h
> +++ b/include/media/v4l2-ctrls.h
> @@ -53,6 +53,8 @@ struct v4l2_ctrl_ops {
> int (*s_ctrl)(struct v4l2_ctrl *ctrl);
> };
>
> +typedef void (*v4l2_ctrl_notify_fnc)(struct v4l2_ctrl *ctrl, void *priv);
> +
> /** struct v4l2_ctrl - The control structure.
> * @node: The list node.
> * @ev_subs: The list of control event subscriptions.
> @@ -72,6 +74,8 @@ struct v4l2_ctrl_ops {
> * set this flag directly.
> * @has_volatiles: If set, then one or more members of the cluster are
> volatile. * Drivers should never touch this flag.
> + * @call_notify: If set, then call the handler's notify function whenever
> the + * control's value changes.
> * @manual_mode_value: If the is_auto flag is set, then this is the value
> * of the auto control that determines if that control is in
> * manual mode. So if the value of the auto control equals this
> @@ -119,6 +123,7 @@ struct v4l2_ctrl {
> unsigned int is_private:1;
> unsigned int is_auto:1;
> unsigned int has_volatiles:1;
> + unsigned int call_notify:1;
> unsigned int manual_mode_value:8;
>
> const struct v4l2_ctrl_ops *ops;
> @@ -177,6 +182,10 @@ struct v4l2_ctrl_ref {
> * control is needed multiple times, so this is a simple
> * optimization.
> * @buckets: Buckets for the hashing. Allows for quick control
> lookup.
> + * @notify: A notify callback that is called whenever the control
changes
> value. + * Note that the handler's lock is held when the notify
function
> + * is called!
> + * @notify_priv: Passed as argument to the v4l2_ctrl notify callback.
> * @nr_of_buckets: Total number of buckets in the array.
> * @error: The error code of the first failed control addition.
> */
> @@ -187,6 +196,8 @@ struct v4l2_ctrl_handler {
> struct list_head ctrl_refs;
> struct v4l2_ctrl_ref *cached;
> struct v4l2_ctrl_ref **buckets;
> + v4l2_ctrl_notify_fnc notify;
> + void *notify_priv;
> u16 nr_of_buckets;
> int error;
> };
> @@ -488,6 +499,20 @@ static inline void v4l2_ctrl_unlock(struct v4l2_ctrl
> *ctrl) mutex_unlock(ctrl->handler->lock);
> }
>
> +/** v4l2_ctrl_notify() - Function to set a notify callback for a control.
> + * @ctrl: The control.
> + * @notify: The callback function.
> + * @priv: The callback private handle, passed as argument to the callback.
> + *
> + * This function sets a callback function for the control. If @ctrl is
> NULL, + * then it will do nothing. If @notify is NULL, then the notify
> callback will + * be removed.
> + *
> + * There can be only one notify. If another already exists, then a WARN_ON
> + * will be issued and the function will do nothing.
> + */
> +void v4l2_ctrl_notify(struct v4l2_ctrl *ctrl, v4l2_ctrl_notify_fnc notify,
> void *priv); +
> /** v4l2_ctrl_g_ctrl() - Helper function to get the control's value from
> within a driver. * @ctrl: The control.
> *
--
Regards,
Laurent Pinchart
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