linux-kernel - [PATCH 4.2.y-ckt 053/211] [media] media/v4l2-ctrls: fix setting autocluster to manual with VIDIOC_S

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Message-Id: <1452023119-25647-54-git-send-email-kamal@canonical.com>
Date:	Tue,  5 Jan 2016 11:42:41 -0800
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Antonio Ospite <ao2@....it>, Hans Verkuil <hans.verkuil@...co.com>,
	Mauro Carvalho Chehab <mchehab@....samsung.com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 4.2.y-ckt 053/211] [media] media/v4l2-ctrls: fix setting autocluster to manual with VIDIOC_S_CTRL

4.2.8-ckt1 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Antonio Ospite <ao2@....it>

commit 759b26a1d916400a1a20948eb964dea6ad0bd9e9 upstream.

Since commit 5d0360a4f027576e5419d4a7c711c9ca0f1be8ca it's not possible
anymore to set auto clusters from auto to manual using VIDIOC_S_CTRL.

For example, setting autogain to manual with gspca/ov534 driver and this
sequence of commands does not work:

  v4l2-ctl --set-ctrl=gain_automatic=1
  v4l2-ctl --list-ctrls | grep gain_automatic
  # The following does not work
  v4l2-ctl --set-ctrl=gain_automatic=0
  v4l2-ctl --list-ctrls | grep gain_automatic

Changing the value using VIDIOC_S_EXT_CTRLS (like qv4l2 does) works
fine.

The apparent cause by looking at the changes in 5d0360a and comparing
with the code path for VIDIOC_S_EXT_CTRLS seems to be that the code in
v4l2-ctrls.c::set_ctrl() is not calling user_to_new() anymore after
calling update_from_auto_cluster(master).

However the root cause of the problem is that calling
update_from_auto_cluster(master) overrides also the _master_ control
state calling cur_to_new() while it was supposed to only update the
volatile controls.

Calling user_to_new() after update_from_auto_cluster(master) was just
masking the original bug by restoring the correct new value of the
master control before making the changes permanent.

Fix the original bug by making update_from_auto_cluster() not override
the new master control value.

Signed-off-by: Antonio Ospite <ao2@....it>
Signed-off-by: Hans Verkuil <hans.verkuil@...co.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@....samsung.com>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 drivers/media/v4l2-core/v4l2-ctrls.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
index 78e7ca7..b2483ae 100644
--- a/drivers/media/v4l2-core/v4l2-ctrls.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls.c
@@ -3058,7 +3058,7 @@ static void update_from_auto_cluster(struct v4l2_ctrl *master)
 {
 	int i;

-	for (i = 0; i < master->ncontrols; i++)
+	for (i = 1; i < master->ncontrols; i++)
 		cur_to_new(master->cluster[i]);
 	if (!call_op(master, g_volatile_ctrl))
 		for (i = 1; i < master->ncontrols; i++)
-- 
1.9.1

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