[PATCH v5 0/3] media: subdev: Add v4l2_subdev_get_frame_desc_passthrough and use it

[PATCH v5 0/3] media: subdev: Add v4l2_subdev_get_frame_desc_passthrough and use it

[Tomi Valkeinen]

When writing the exact same code the third time for Renesas, I thought
we probably need a helper.

 Tomi

Signed-off-by: Tomi Valkeinen <tomi.valkeinen+renesas@ideasonboard.com>
---
Changes in v5:
- Minor code cleanups which do not change functionality
- Rewrote the kernel doc
- Fix mentions of 'v4l2_get_frame_desc' op, as it's 'get_frame_desc'
- Rebase on v7.0-rc2
- Link to v4: https://lore.kernel.org/r/20250324-frame-desc-passthrough-v4-0-dbe2412297cc@ideasonboard.com

Changes in v4:
- Update the helper name in commit descriptions too
- Link to v3: https://lore.kernel.org/r/20250324-frame-desc-passthrough-v3-0-993839a1f9b3@ideasonboard.com

Changes in v3:
- Rename the helper to v4l2_subdev_get_frame_desc_passthrough()
- Check for fd->entry[] array overflow
- Add error prints (with dev_dbg)
- Link to v2: https://lore.kernel.org/r/20250219-frame-desc-passthrough-v2-0-5135d57ecd6a@ideasonboard.com

Changes in v2:
- Fix "uninitialized symbol 'ret'"
- Reorder local variables
- Link to v1: https://lore.kernel.org/r/20250218-frame-desc-passthrough-v1-0-a32458f53714@ideasonboard.com

---
Tomi Valkeinen (3):
      media: subdev: Add v4l2_subdev_get_frame_desc_passthrough helper
      media: i2c: ds90ub953: Use v4l2_subdev_get_frame_desc_passthrough
      media: i2c: ds90ub913: Use v4l2_subdev_get_frame_desc_passthrough

 drivers/media/i2c/ds90ub913.c         |  59 +-----------------
 drivers/media/i2c/ds90ub953.c         |  61 +------------------
 drivers/media/v4l2-core/v4l2-subdev.c | 111 ++++++++++++++++++++++++++++++++++
 include/media/v4l2-subdev.h           |  28 +++++++++
 4 files changed, 141 insertions(+), 118 deletions(-)
---
base-commit: 11439c4635edd669ae435eec308f4ab8a0804808
change-id: 20250218-frame-desc-passthrough-66805e413974

Best regards,
-- 
Tomi Valkeinen <tomi.valkeinen+renesas@ideasonboard.com>

[PATCH v5 1/3] media: subdev: Add v4l2_subdev_get_frame_desc_passthrough helper

[Tomi Valkeinen]

Add a helper for v4l2_subdev_pad_ops.get_frame_desc operation. The
helper can be used when the subdevice directly passes through the
streams.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen+renesas@ideasonboard.com>
---
 drivers/media/v4l2-core/v4l2-subdev.c | 111 ++++++++++++++++++++++++++++++++++
 include/media/v4l2-subdev.h           |  28 +++++++++
 2 files changed, 139 insertions(+)

diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index 32e6f60e26c7..2757378c628a 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -2545,6 +2545,117 @@ 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)
+{
+	struct media_pad *local_sink_pad;
+	struct v4l2_subdev_route *route;
+	struct v4l2_subdev_state *state;
+	struct device *dev = sd->dev;
+	int ret = 0;
+
+	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;
+		bool have_source_fd = false;
+
+		if (!(local_sink_pad->flags & MEDIA_PAD_FL_SINK))
+			continue;
+
+		/*
+		 * Copy frame desc entries for the streams going from the sink
+		 * pad to the requested pad
+		 */
+		for_each_active_route(&state->routing, route) {
+			struct v4l2_mbus_frame_desc_entry *source_entry = NULL;
+			struct media_pad *remote_source_pad;
+			struct v4l2_subdev *remote_sd;
+
+			if (route->source_pad != pad ||
+			    route->sink_pad != local_sink_pad->index)
+				continue;
+
+			if (!have_source_fd) {
+				remote_source_pad = media_pad_remote_pad_unique(local_sink_pad);
+				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;
+				}
+
+				remote_sd = media_entity_to_v4l2_subdev(remote_source_pad->entity);
+				if (!remote_sd) {
+					ret = -EINVAL;
+					goto out_unlock;
+				}
+
+				ret = v4l2_subdev_call(remote_sd, pad,
+						       get_frame_desc,
+						       remote_source_pad->index,
+						       &source_fd);
+				if (ret) {
+					dev_err(dev,
+						"Failed to get frame desc from remote subdev %s\n",
+						remote_sd->name);
+					goto out_unlock;
+				}
+
+				have_source_fd = true;
+
+				if (fd->num_entries == 0) {
+					fd->type = source_fd.type;
+				} else if (fd->type != source_fd.type) {
+					dev_err(dev,
+						"Frame desc type mismatch: %u != %u\n",
+						fd->type, source_fd.type);
+					ret = -EPIPE;
+					goto out_unlock;
+				}
+			}
+
+			for (unsigned int i = 0; i < source_fd.num_entries; i++) {
+				if (source_fd.entry[i].stream == route->sink_stream) {
+					source_entry = &source_fd.entry[i];
+					break;
+				}
+			}
+
+			if (!source_entry) {
+				dev_dbg(dev,
+					"Failed to find stream %u from source frame desc\n",
+					route->sink_stream);
+				ret = -EPIPE;
+				goto out_unlock;
+			}
+
+			if (fd->num_entries >= V4L2_FRAME_DESC_ENTRY_MAX) {
+				dev_dbg(dev, "Frame desc entry limit reached\n");
+				ret = -ENOSPC;
+				goto out_unlock;
+			}
+
+			fd->entry[fd->num_entries] = *source_entry;
+
+			fd->entry[fd->num_entries].stream = route->source_stream;
+
+			fd->num_entries++;
+		}
+	}
+
+out_unlock:
+	v4l2_subdev_unlock_state(state);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(v4l2_subdev_get_frame_desc_passthrough);
+
 #endif /* CONFIG_VIDEO_V4L2_SUBDEV_API */
 
 #endif /* CONFIG_MEDIA_CONTROLLER */
diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index a37d9a847196..23c03ba7f84c 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -1722,6 +1722,34 @@ 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
+ * @sd: The subdevice
+ * @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.
+ *
+ * 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
+ * entries for streams that are routed to the given source pad according to the
+ * subdevice's routing table. Each entry is copied as-is from the upstream
+ * source, with the exception of the 'stream' field which is remapped to the
+ * source stream ID from the routing table.
+ *
+ * The frame desc type is taken from the first upstream source. If multiple
+ * sink pads are involved and the upstream sources report different frame desc
+ * types, -EPIPE is returned.
+ *
+ * Return: 0 on success, or a negative error code otherwise.
+ */
+int v4l2_subdev_get_frame_desc_passthrough(struct v4l2_subdev *sd,
+					   unsigned int pad,
+					   struct v4l2_mbus_frame_desc *fd);
+
 #endif /* CONFIG_VIDEO_V4L2_SUBDEV_API */
 
 #endif /* CONFIG_MEDIA_CONTROLLER */

-- 
2.43.0

[PATCH v5 2/3] media: i2c: ds90ub953: Use v4l2_subdev_get_frame_desc_passthrough

[Tomi Valkeinen]

Use the new v4l2_subdev_get_frame_desc_passthrough helper for
.get_frame_desc.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen+renesas@ideasonboard.com>
---
 drivers/media/i2c/ds90ub953.c | 61 +------------------------------------------
 1 file changed, 1 insertion(+), 60 deletions(-)

diff --git a/drivers/media/i2c/ds90ub953.c b/drivers/media/i2c/ds90ub953.c
index daefdb108fbf..a8ab67f4137f 100644
--- a/drivers/media/i2c/ds90ub953.c
+++ b/drivers/media/i2c/ds90ub953.c
@@ -424,65 +424,6 @@ static int ub953_set_routing(struct v4l2_subdev *sd,
 	return _ub953_set_routing(sd, state, routing);
 }
 
-static int ub953_get_frame_desc(struct v4l2_subdev *sd, unsigned int pad,
-				struct v4l2_mbus_frame_desc *fd)
-{
-	struct ub953_data *priv = sd_to_ub953(sd);
-	struct v4l2_mbus_frame_desc source_fd;
-	struct v4l2_subdev_route *route;
-	struct v4l2_subdev_state *state;
-	int ret;
-
-	if (pad != UB953_PAD_SOURCE)
-		return -EINVAL;
-
-	ret = v4l2_subdev_call(priv->source_sd, pad, get_frame_desc,
-			       priv->source_sd_pad, &source_fd);
-	if (ret)
-		return ret;
-
-	fd->type = V4L2_MBUS_FRAME_DESC_TYPE_CSI2;
-
-	state = v4l2_subdev_lock_and_get_active_state(sd);
-
-	for_each_active_route(&state->routing, route) {
-		struct v4l2_mbus_frame_desc_entry *source_entry = NULL;
-		unsigned int i;
-
-		if (route->source_pad != pad)
-			continue;
-
-		for (i = 0; i < source_fd.num_entries; i++) {
-			if (source_fd.entry[i].stream == route->sink_stream) {
-				source_entry = &source_fd.entry[i];
-				break;
-			}
-		}
-
-		if (!source_entry) {
-			dev_err(&priv->client->dev,
-				"Failed to find stream from source frame desc\n");
-			ret = -EPIPE;
-			goto out_unlock;
-		}
-
-		fd->entry[fd->num_entries].stream = route->source_stream;
-		fd->entry[fd->num_entries].flags = source_entry->flags;
-		fd->entry[fd->num_entries].length = source_entry->length;
-		fd->entry[fd->num_entries].pixelcode = source_entry->pixelcode;
-		fd->entry[fd->num_entries].bus.csi2.vc =
-			source_entry->bus.csi2.vc;
-		fd->entry[fd->num_entries].bus.csi2.dt =
-			source_entry->bus.csi2.dt;
-
-		fd->num_entries++;
-	}
-
-out_unlock:
-	v4l2_subdev_unlock_state(state);
-
-	return ret;
-}
 
 static int ub953_set_fmt(struct v4l2_subdev *sd,
 			 struct v4l2_subdev_state *state,
@@ -694,7 +635,7 @@ static const struct v4l2_subdev_pad_ops ub953_pad_ops = {
 	.enable_streams = ub953_enable_streams,
 	.disable_streams = ub953_disable_streams,
 	.set_routing = ub953_set_routing,
-	.get_frame_desc = ub953_get_frame_desc,
+	.get_frame_desc = v4l2_subdev_get_frame_desc_passthrough,
 	.get_fmt = v4l2_subdev_get_fmt,
 	.set_fmt = ub953_set_fmt,
 };

-- 
2.43.0

[PATCH v5 3/3] media: i2c: ds90ub913: Use v4l2_subdev_get_frame_desc_passthrough

[Tomi Valkeinen]

Use the new v4l2_subdev_get_frame_desc_passthrough helper for
.get_frame_desc.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen+renesas@ideasonboard.com>
---
 drivers/media/i2c/ds90ub913.c | 59 +------------------------------------------
 1 file changed, 1 insertion(+), 58 deletions(-)

diff --git a/drivers/media/i2c/ds90ub913.c b/drivers/media/i2c/ds90ub913.c
index e97e499b04e6..49aa5f4a172c 100644
--- a/drivers/media/i2c/ds90ub913.c
+++ b/drivers/media/i2c/ds90ub913.c
@@ -372,63 +372,6 @@ static int ub913_set_routing(struct v4l2_subdev *sd,
 	return _ub913_set_routing(sd, state, routing);
 }
 
-static int ub913_get_frame_desc(struct v4l2_subdev *sd, unsigned int pad,
-				struct v4l2_mbus_frame_desc *fd)
-{
-	struct ub913_data *priv = sd_to_ub913(sd);
-	const struct v4l2_subdev_krouting *routing;
-	struct v4l2_mbus_frame_desc source_fd;
-	struct v4l2_subdev_route *route;
-	struct v4l2_subdev_state *state;
-	int ret;
-
-	if (pad != UB913_PAD_SOURCE)
-		return -EINVAL;
-
-	ret = v4l2_subdev_call(priv->source_sd, pad, get_frame_desc,
-			       priv->source_sd_pad, &source_fd);
-	if (ret)
-		return ret;
-
-	fd->type = V4L2_MBUS_FRAME_DESC_TYPE_PARALLEL;
-
-	state = v4l2_subdev_lock_and_get_active_state(sd);
-
-	routing = &state->routing;
-
-	for_each_active_route(routing, route) {
-		unsigned int i;
-
-		if (route->source_pad != pad)
-			continue;
-
-		for (i = 0; i < source_fd.num_entries; i++) {
-			if (source_fd.entry[i].stream == route->sink_stream)
-				break;
-		}
-
-		if (i == source_fd.num_entries) {
-			dev_err(&priv->client->dev,
-				"Failed to find stream from source frame desc\n");
-			ret = -EPIPE;
-			goto out_unlock;
-		}
-
-		fd->entry[fd->num_entries].stream = route->source_stream;
-		fd->entry[fd->num_entries].flags = source_fd.entry[i].flags;
-		fd->entry[fd->num_entries].length = source_fd.entry[i].length;
-		fd->entry[fd->num_entries].pixelcode =
-			source_fd.entry[i].pixelcode;
-
-		fd->num_entries++;
-	}
-
-out_unlock:
-	v4l2_subdev_unlock_state(state);
-
-	return ret;
-}
-
 static int ub913_set_fmt(struct v4l2_subdev *sd,
 			 struct v4l2_subdev_state *state,
 			 struct v4l2_subdev_format *format)
@@ -544,7 +487,7 @@ static const struct v4l2_subdev_pad_ops ub913_pad_ops = {
 	.enable_streams = ub913_enable_streams,
 	.disable_streams = ub913_disable_streams,
 	.set_routing = ub913_set_routing,
-	.get_frame_desc = ub913_get_frame_desc,
+	.get_frame_desc = v4l2_subdev_get_frame_desc_passthrough,
 	.get_fmt = v4l2_subdev_get_fmt,
 	.set_fmt = ub913_set_fmt,
 };

-- 
2.43.0

Re: [v5,0/3] media: subdev: Add v4l2_subdev_get_frame_desc_passthrough and use it

[Tomi Valkeinen]

Hi,

On 11/03/2026 17:45, Patchwork Integration wrote:
> Dear Tomi Valkeinen:
> 
> Thanks for your patches! Unfortunately the Media CI robot detected some
> issues:
> 
> 
> 
> Please fix your series, and upload a new version. If you have a patchwork
> account, do not forget to mark the current series as Superseded.
> 
> For more details, check the full report at:
> https://linux-media.pages.freedesktop.org/-/users/patchwork/-/jobs/94963445/artifacts/report.htm .

I'm having trouble parsing this. Is it a CI issue?

 Tomi

Re: [v5,0/3] media: subdev: Add v4l2_subdev_get_frame_desc_passthrough and use it

[Sakari Ailus]

Moi,

On Wed, Mar 11, 2026 at 06:33:47PM +0200, Tomi Valkeinen wrote:
> Hi,
> 
> On 11/03/2026 17:45, Patchwork Integration wrote:
> > Dear Tomi Valkeinen:
> > 
> > Thanks for your patches! Unfortunately the Media CI robot detected some
> > issues:
> > 
> > 
> > 
> > Please fix your series, and upload a new version. If you have a patchwork
> > account, do not forget to mark the current series as Superseded.
> > 
> > For more details, check the full report at:
> > https://linux-media.pages.freedesktop.org/-/users/patchwork/-/jobs/94963445/artifacts/report.htm .
> 
> I'm having trouble parsing this. Is it a CI issue?

There are issues in that reporting part. Look at the raw output instead.

-- 
Sakari Ailus

Re: [PATCH v5 0/3] media: subdev: Add v4l2_subdev_get_frame_desc_passthrough and use it

[Sakari Ailus]

Moi,

On Wed, Mar 11, 2026 at 02:17:18PM +0200, Tomi Valkeinen wrote:
> When writing the exact same code the third time for Renesas, I thought
> we probably need a helper.
> 
>  Tomi
> 
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen+renesas@ideasonboard.com>

Can you send follow-ups to v4? V4 is already in my PR to Hans.

-- 
Terveisin,

Sakari Ailus

Re: [PATCH v5 0/3] media: subdev: Add v4l2_subdev_get_frame_desc_passthrough and use it

[Tomi Valkeinen]

Hi,

On 11/03/2026 20:11, Sakari Ailus wrote:
> Moi,
> 
> On Wed, Mar 11, 2026 at 02:17:18PM +0200, Tomi Valkeinen wrote:
>> When writing the exact same code the third time for Renesas, I thought
>> we probably need a helper.
>>
>>  Tomi
>>
>> Signed-off-by: Tomi Valkeinen <tomi.valkeinen+renesas@ideasonboard.com>
> 
> Can you send follow-ups to v4? V4 is already in my PR to Hans.
> 

I have sent
https://lore.kernel.org/all/20260312-frame-desc-passthrough-impro-v1-0-30f64d637a3a%40ideasonboard.com/

 Tomi