Re: [PATCH v3 3/9] media: subdev: Add checks for subdev features

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Hi Tomi,

On 10/04/24 6:05 pm, Tomi Valkeinen wrote:
Add some checks to verify that the subdev driver implements required

A subdevice that supports streams (V4L2_SUBDEV_FL_STREAMS) must do one
of the following:

- Implement neither .enable/disable_streams() nor .s_stream(), if the
   subdev is part of a video driver that uses an internal method to
   enable the subdev.
- Implement only .enable/disable_streams(), if support for legacy
   sink-side subdevices is not needed.
- Implement .enable/disable_streams() and .s_stream(), if support for
   legacy sink-side subdevices is needed.

At the moment the framework doesn't check this requirement. Add the

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@xxxxxxxxxxxxxxxx>

The code looks aligned with the restrictions mentioned in the commit message.

Only one question in case 3), does the .s_stream() needs to be helper function I think, can we (or do we) need to check that as well?

Reviewed-by: Umang Jain <umang.jain@xxxxxxxxxxxxxxxx>

  drivers/media/v4l2-core/v4l2-subdev.c | 27 +++++++++++++++++++++++++++
  1 file changed, 27 insertions(+)

diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index 4a531c2b16c4..606a909cd778 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -1533,6 +1533,33 @@ int __v4l2_subdev_init_finalize(struct v4l2_subdev *sd, const char *name,
  				struct lock_class_key *key)
  	struct v4l2_subdev_state *state;
+	struct device *dev = sd->dev;
+	bool has_disable_streams;
+	bool has_enable_streams;
+	bool has_s_stream;
+	/* Check that the subdevice implements the required features */
+	has_s_stream = v4l2_subdev_has_op(sd, video, s_stream);
+	has_enable_streams = v4l2_subdev_has_op(sd, pad, enable_streams);
+	has_disable_streams = v4l2_subdev_has_op(sd, pad, disable_streams);
+	if (has_enable_streams != has_disable_streams) {
+		dev_err(dev,
+			"subdev '%s' must implement both or neither of .enable_streams() and .disable_streams()\n",
+			sd->name);
+		return -EINVAL;
+	}
+	if (sd->flags & V4L2_SUBDEV_FL_STREAMS) {
+		if (has_s_stream && !has_enable_streams) {
+			dev_err(dev,
+				"subdev '%s' must implement .enable/disable_streams()\n",
+				sd->name);
+			return -EINVAL;
+		}
+	}
state = __v4l2_subdev_state_alloc(sd, name, key);
  	if (IS_ERR(state))

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