media: add tuner standby op, use where needed

The v4l2_subdev core s_power op was used for two different things: power on/off
sensors or video decoders/encoders and to put a tuner in standby (and only the
tuner!). There is no 'tuner wakeup' op, that's done automatically when the tuner
is accessed.

The danger with calling (s_power, 0) to put a tuner into standby is that it is
usually broadcast for all subdevs. So a video receiver subdev that supports
s_power will also be powered off, and since there is no corresponding (s_power, 1)
they will never be powered on again.

In addition, this is specifically meant for tuners only since they draw the most
current.

This patch adds a new tuner op called 'standby' and replaces all calls to
(core, s_power, 0) by (tuner, standby). This prevents confusion between the two
uses of s_power. Note that there is no overlap: bridge drivers either just want
to put the tuner into standby, or they deal with powering on/off sensors. Never
both.

This also makes it easier to replace s_power for the remaining bridge drivers
with some PM code later.

Whether we want something cleaner for tuners in the future is a separate topic.
There is a lot of legacy code surrounding tuners, and I am very hesitant about
making changes there.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index 2561222322d5..9102d6ca566e 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -224,6 +224,9 @@ struct v4l2_subdev_core_ops {
  * struct v4l2_subdev_tuner_ops - Callbacks used when v4l device was opened
  *	in radio mode.
  *
+ * @standby: puts the tuner in standby mode. It will be woken up
+ *	     automatically the next time it is used.
+ *
  * @s_radio: callback that switches the tuner to radio mode.
  *	     drivers should explicitly call it when a tuner ops should
  *	     operate on radio mode, before being able to handle it.
@@ -268,6 +271,7 @@ struct v4l2_subdev_core_ops {
  *	  }
  */
 struct v4l2_subdev_tuner_ops {
+	int (*standby)(struct v4l2_subdev *sd);
 	int (*s_radio)(struct v4l2_subdev *sd);
 	int (*s_frequency)(struct v4l2_subdev *sd, const struct v4l2_frequency *freq);
 	int (*g_frequency)(struct v4l2_subdev *sd, struct v4l2_frequency *freq);