V4L/DVB (3254): Don't reprogram the video standard if it is unchanged.

- Don't reprogram the video standard if the new standard
equals the old standard.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@brturbo.com.br>

1 files changed, 10 insertions, 0 deletions

diff --git a/drivers/media/video/saa7115.c b/drivers/media/video/saa7115.c
index 3e4e5584c5d0..5d33d0922e79 100644
--- a/drivers/media/video/saa7115.c
+++ b/drivers/media/video/saa7115.c
@@ -668,6 +668,16 @@ static void saa7115_set_v4lstd(struct i2c_client *client, v4l2_std_id std)
         struct saa7115_state *state = i2c_get_clientdata(client);
         int taskb = saa7115_read(client, 0x80) & 0x10;
 
+        /* Prevent unnecessary standard changes. During a standard
+           change the I-Port is temporarily disabled. Any devices
+           reading from that port can get confused.
+           Note that VIDIOC_S_STD is also used to switch from
+           radio to TV mode, so if a VIDIOC_S_STD is broadcast to
+           all I2C devices then you do not want to have an unwanted
+           side-effect here. */
+        if (std == state->std)
+                return;
+
         // This works for NTSC-M, SECAM-L and the 50Hz PAL variants.
         if (std & V4L2_STD_525_60) {
                 saa7115_dbg("decoder set standard 60 Hz\n");