From 1e42d384aa19e06410be52bd05cfc159722c0b7f Mon Sep 17 00:00:00 2001 From: Paul Kocialkowski Date: Thu, 25 Jul 2019 14:55:59 -0400 Subject: [PATCH] media: v4l2-ctrl: Add a comment on why we zero out compound controls fields Since it's not necessarily very explicit why we need to zero some fields in std_validate_compound, add a comment before the function to explain why, which should help as a reminder. Signed-off-by: Paul Kocialkowski Signed-off-by: Hans Verkuil Signed-off-by: Mauro Carvalho Chehab --- drivers/media/v4l2-core/v4l2-ctrls.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c index 76fa2db..cd1ae01 100644 --- a/drivers/media/v4l2-core/v4l2-ctrls.c +++ b/drivers/media/v4l2-core/v4l2-ctrls.c @@ -1645,6 +1645,10 @@ static void std_log(const struct v4l2_ctrl *ctrl) #define zero_padding(s) \ memset(&(s).padding, 0, sizeof((s).padding)) +/* + * Compound controls validation requires setting unused fields/flags to zero + * in order to properly detect unchanged controls with std_equal's memcmp. + */ static int std_validate_compound(const struct v4l2_ctrl *ctrl, u32 idx, union v4l2_ctrl_ptr ptr) { -- 2.7.4