media: subdev: Split v4l2_subdev_get_frame_desc_passthrough() into locked and unlocked

The recently added v4l2_subdev_get_frame_desc_passthrough() can be used
directly as an implementation for .get_frame_desc subdev op. However, in
some cases the drivers may want to add some customizations, while the
bulk of the work is still identical to what
v4l2_subdev_get_frame_desc_passthrough() does. Current locking scheme
makes this impossible to do properly.

Split v4l2_subdev_get_frame_desc_passthrough() into two functions:

__v4l2_subdev_get_frame_desc_passthrough(), which takes a locked subdev
state as a parameter, instead of locking and getting the active state
internally. Other than that, it does the same as
v4l2_subdev_get_frame_desc_passthrough() used to do.

v4l2_subdev_get_frame_desc_passthrough(), which locks the active state
and calls __v4l2_subdev_get_frame_desc_passthrough().

In other words, v4l2_subdev_get_frame_desc_passthrough() works as
before, but drivers can now alternatively add custom .get_frame_desc
code and call v4l2_subdev_get_frame_desc_passthrough().

An example use case is with DS90UB953 serializer: in normal use the
serializer passes through everything, but when test-pattern-generator
(TPG) is used, an internal TPG source is used. After this commit, the
UB953 get_frame_desc() can lock the state, look at the routing table to
see if we're in normal or TPG mode, then either call
__v4l2_subdev_get_frame_desc_passthrough() if in normal mode, or
construct a TPG frame desc if in TPG mode.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen+renesas@ideasonboard.com>
[Sakari Ailus: Rebase on an earlier remote source pad error code fix.]
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>

1 files changed, 33 insertions, 5 deletions

diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index 23c03ba7f84c..d256b7ec8f84 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -1723,15 +1723,15 @@ int v4l2_subdev_disable_streams(struct v4l2_subdev *sd, u32 pad,
 int v4l2_subdev_s_stream_helper(struct v4l2_subdev *sd, int enable);
 
 /**
- * v4l2_subdev_get_frame_desc_passthrough() - Helper to implement the subdev
- *	get_frame_desc operation in simple passthrough cases
+ * __v4l2_subdev_get_frame_desc_passthrough - Helper to implement the
+ *	subdev get_frame_desc operation in simple passthrough cases
  * @sd: The subdevice
+ * @state: The locked subdevice active state
  * @pad: The source pad index
  * @fd: The mbus frame desc
  *
- * This helper implements get_frame_desc operation for subdevices that pass
- * streams through without modification. It can be assigned directly as the
- * .get_frame_desc callback in &v4l2_subdev_pad_ops.
+ * This helper implements the get_frame_desc operation for subdevices that pass
+ * streams through without modification.
  *
  * The helper iterates over the subdevice's sink pads, calls get_frame_desc on
  * the remote subdevice connected to each sink pad, and collects the frame desc
@@ -1744,6 +1744,34 @@ int v4l2_subdev_s_stream_helper(struct v4l2_subdev *sd, int enable);
  * sink pads are involved and the upstream sources report different frame desc
  * types, -EPIPE is returned.
  *
+ * The caller must hold the subdevice's active state lock. This variant is
+ * intended for drivers that need to perform additional work around the
+ * passthrough frame descriptor collection. Drivers that do not need any
+ * customization should use v4l2_subdev_get_frame_desc_passthrough() instead.
+ *
+ * Return: 0 on success, or a negative error code otherwise.
+ */
+int __v4l2_subdev_get_frame_desc_passthrough(struct v4l2_subdev *sd,
+					     struct v4l2_subdev_state *state,
+					     unsigned int pad,
+					     struct v4l2_mbus_frame_desc *fd);
+
+/**
+ * v4l2_subdev_get_frame_desc_passthrough() - Helper to implement the subdev
+ *	get_frame_desc operation in simple passthrough cases
+ * @sd: The subdevice
+ * @pad: The source pad index
+ * @fd: The mbus frame desc
+ *
+ * This function locks the subdevice's active state, calls
+ * __v4l2_subdev_get_frame_desc_passthrough(), and unlocks the state.
+ *
+ * This function can be assigned directly as the .get_frame_desc callback in
+ * &v4l2_subdev_pad_ops for subdevices that pass streams through without
+ * modification. Drivers that need to perform additional work should use
+ * __v4l2_subdev_get_frame_desc_passthrough() in their custom
+ * .get_frame_desc implementation instead.
+ *
  * Return: 0 on success, or a negative error code otherwise.
  */
 int v4l2_subdev_get_frame_desc_passthrough(struct v4l2_subdev *sd,