[media] v4l2-ctrls: compare values only once

When setting a control the control's new value is compared to the current
value twice: once by new_to_cur(), once by cluster_changed(). Not a big
deal when dealing with simple values, but it can be a problem when dealing
with compound types or arrays. So fix this: cluster_changed() sets the
has_changed flag, which is used by new_to_cur() instead of having to do
another compare.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Reviewed-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
index e7e0bea..1b4d37c 100644 (file)
--- a/drivers/media/v4l2-core/v4l2-ctrls.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls.c
@@ -1424,8 +1424,11 @@ static void new_to_cur(struct v4l2_fh *fh, struct v4l2_ctrl *ctrl, u32 ch_flags)
 
        if (ctrl == NULL)
                return;
-       changed = !ctrl->type_ops->equal(ctrl, ctrl->p_cur, ctrl->p_new);
-       ptr_to_ptr(ctrl, ctrl->p_new, ctrl->p_cur);
+
+       /* has_changed is set by cluster_changed */
+       changed = ctrl->has_changed;
+       if (changed)
+               ptr_to_ptr(ctrl, ctrl->p_new, ctrl->p_cur);
 
        if (ch_flags & V4L2_EVENT_CTRL_CH_FLAGS) {
                /* Note: CH_FLAGS is only set for auto clusters. */
@@ -1462,17 +1465,19 @@ static void cur_to_new(struct v4l2_ctrl *ctrl)
    value that differs from the current value. */
 static int cluster_changed(struct v4l2_ctrl *master)
 {
-       int diff = 0;
+       bool changed = false;
        int i;
 
-       for (i = 0; !diff && i < master->ncontrols; i++) {
+       for (i = 0; i < master->ncontrols; i++) {
                struct v4l2_ctrl *ctrl = master->cluster[i];
 
                if (ctrl == NULL)
                        continue;
-               diff = !ctrl->type_ops->equal(ctrl, ctrl->p_cur, ctrl->p_new);
+               ctrl->has_changed = !ctrl->type_ops->equal(ctrl,
+                                               ctrl->p_cur, ctrl->p_new);
+               changed |= ctrl->has_changed;
        }
-       return diff;
+       return changed;
 }
 
 /* Control range checking */

diff --git a/include/media/v4l2-ctrls.h b/include/media/v4l2-ctrls.h
index ddd9fdf..a38bd55 100644 (file)
--- a/include/media/v4l2-ctrls.h
+++ b/include/media/v4l2-ctrls.h
@@ -96,6 +96,8 @@ typedef void (*v4l2_ctrl_notify_fnc)(struct v4l2_ctrl *ctrl, void *priv);
   * @is_new:   Set when the user specified a new value for this control. It
   *            is also set when called from v4l2_ctrl_handler_setup. Drivers
   *            should never set this flag.
+  * @has_changed: Set when the current value differs from the new value. Drivers
+  *            should never use this flag.
   * @is_private: If set, then this control is private to its handler and it
   *            will not be added to any other handlers. Drivers can set
   *            this flag.
@@ -158,6 +160,7 @@ struct v4l2_ctrl {
        unsigned int done:1;
 
        unsigned int is_new:1;
+       unsigned int has_changed:1;
        unsigned int is_private:1;
        unsigned int is_auto:1;
        unsigned int is_int:1;