[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>

1 files changed, 11 insertions, 6 deletions

diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
index e7e0beab7048..1b4d37ce4afe 100644
--- 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 */