[PATCH v2 3/3] media: subdev: Split v4l2_subdev_get_frame_desc_passthrough() into locked and unlocked

[Tomi Valkeinen]

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@xxxxxxxxxxxxxxxx>
---
 drivers/media/v4l2-core/v4l2-subdev.c | 48 ++++++++++++++++++++---------------
 include/media/v4l2-subdev.h           | 38 +++++++++++++++++++++++----
 2 files changed, 61 insertions(+), 25 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index 2757378c628a..b73ccd1c83d2 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -2545,21 +2545,21 @@ int v4l2_subdev_s_stream_helper(struct v4l2_subdev *sd, int enable)
 }
 EXPORT_SYMBOL_GPL(v4l2_subdev_s_stream_helper);
 
-int v4l2_subdev_get_frame_desc_passthrough(struct v4l2_subdev *sd,
-					   unsigned int pad,
-					   struct v4l2_mbus_frame_desc *fd)
+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)
 {
 	struct media_pad *local_sink_pad;
 	struct v4l2_subdev_route *route;
-	struct v4l2_subdev_state *state;
 	struct device *dev = sd->dev;
 	int ret = 0;
 
+	lockdep_assert_held(state->lock);
+
 	if (WARN_ON(!(sd->entity.pads[pad].flags & MEDIA_PAD_FL_SOURCE)))
 		return -EINVAL;
 
-	state = v4l2_subdev_lock_and_get_active_state(sd);
-
 	/* Iterate over sink pads */
 	media_entity_for_each_pad(&sd->entity, local_sink_pad) {
 		struct v4l2_mbus_frame_desc source_fd;
@@ -2586,15 +2586,12 @@ int v4l2_subdev_get_frame_desc_passthrough(struct v4l2_subdev *sd,
 				if (!remote_source_pad) {
 					dev_dbg(dev, "Failed to find remote pad for sink pad %u\n",
 						local_sink_pad->index);
-					ret = -EINVAL;
-					goto out_unlock;
+					return -EINVAL;
 				}
 
 				remote_sd = media_entity_to_v4l2_subdev(remote_source_pad->entity);
-				if (!remote_sd) {
-					ret = -EINVAL;
-					goto out_unlock;
-				}
+				if (!remote_sd)
+					return -EINVAL;
 
 				ret = v4l2_subdev_call(remote_sd, pad,
 						       get_frame_desc,
@@ -2604,7 +2601,7 @@ int v4l2_subdev_get_frame_desc_passthrough(struct v4l2_subdev *sd,
 					dev_err(dev,
 						"Failed to get frame desc from remote subdev %s\n",
 						remote_sd->name);
-					goto out_unlock;
+					return ret;
 				}
 
 				have_source_fd = true;
@@ -2615,8 +2612,7 @@ int v4l2_subdev_get_frame_desc_passthrough(struct v4l2_subdev *sd,
 					dev_err(dev,
 						"Frame desc type mismatch: %u != %u\n",
 						fd->type, source_fd.type);
-					ret = -EPIPE;
-					goto out_unlock;
+					return -EPIPE;
 				}
 			}
 
@@ -2631,14 +2627,12 @@ int v4l2_subdev_get_frame_desc_passthrough(struct v4l2_subdev *sd,
 				dev_dbg(dev,
 					"Failed to find stream %u from source frame desc\n",
 					route->sink_stream);
-				ret = -EPIPE;
-				goto out_unlock;
+				return -EPIPE;
 			}
 
 			if (fd->num_entries >= V4L2_FRAME_DESC_ENTRY_MAX) {
 				dev_dbg(dev, "Frame desc entry limit reached\n");
-				ret = -ENOSPC;
-				goto out_unlock;
+				return -ENOSPC;
 			}
 
 			fd->entry[fd->num_entries] = *source_entry;
@@ -2649,7 +2643,21 @@ int v4l2_subdev_get_frame_desc_passthrough(struct v4l2_subdev *sd,
 		}
 	}
 
-out_unlock:
+	return 0;
+}
+EXPORT_SYMBOL_GPL(__v4l2_subdev_get_frame_desc_passthrough);
+
+int v4l2_subdev_get_frame_desc_passthrough(struct v4l2_subdev *sd,
+					   unsigned int pad,
+					   struct v4l2_mbus_frame_desc *fd)
+{
+	struct v4l2_subdev_state *state;
+	int ret;
+
+	state = v4l2_subdev_lock_and_get_active_state(sd);
+
+	ret = __v4l2_subdev_get_frame_desc_passthrough(sd, state, pad, fd);
+
 	v4l2_subdev_unlock_state(state);
 
 	return ret;
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,

-- 
2.43.0