From: "Guoniu.zhou" <guoniu.zhou@nxp.com>

Implement the get_frame_desc pad operation for the crossbar subdevice
to propagate frame descriptor information from the source subdevice to
downstream ISI channels.

This allows the ISI driver to retrieve virtual channel information and
other stream parameters from the connected upstream, which is required
for proper virtual channel routing on platforms supporting multiple VCs.

Signed-off-by: Guoniu.zhou <guoniu.zhou@nxp.com>
---
Changes in v3:
- New patch added based on feedback from Laurent Pinchart
---
 .../platform/nxp/imx8-isi/imx8-isi-crossbar.c      | 97 ++++++++++++++++++++++
 1 file changed, 97 insertions(+)

diff --git a/drivers/media/platform/nxp/imx8-isi/imx8-isi-crossbar.c b/drivers/media/platform/nxp/imx8-isi/imx8-isi-crossbar.c
index 605a45124103..2e98fedbabc2 100644
--- a/drivers/media/platform/nxp/imx8-isi/imx8-isi-crossbar.c
+++ b/drivers/media/platform/nxp/imx8-isi/imx8-isi-crossbar.c
@@ -306,6 +306,102 @@ static int mxc_isi_crossbar_set_fmt(struct v4l2_subdev *sd,
 	return 0;
 }
 
+static int mxc_isi_get_frame_desc(struct v4l2_subdev *sd, unsigned int pad,
+				  struct v4l2_mbus_frame_desc *fd)
+{
+	struct mxc_isi_crossbar *xbar = to_isi_crossbar(sd);
+	struct device *dev = xbar->isi->dev;
+	struct v4l2_subdev_route *route;
+	struct v4l2_subdev_state *state;
+	int ret = 0;
+
+	if (pad < xbar->num_sinks)
+		return -EINVAL;
+
+	memset(fd, 0, sizeof(*fd));
+
+	state = v4l2_subdev_lock_and_get_active_state(sd);
+
+	/*
+	 * Iterate over all active routes. For each route going through the
+	 * requested source pad, get the frame descriptor from the connected
+	 * source subdev, find the corresponding stream entry, and add it to
+	 * the output frame descriptor with the routed stream ID.
+	 */
+	for_each_active_route(&state->routing, route) {
+		struct v4l2_mbus_frame_desc source_fd;
+		struct v4l2_subdev *remote_sd;
+		struct media_pad *remote_pad;
+		unsigned int i;
+
+		if (route->source_pad != pad)
+			continue;
+
+		/* Find the remote subdev connected to this sink pad */
+		remote_pad = media_pad_remote_pad_first(&xbar->pads[route->sink_pad]);
+		if (!remote_pad) {
+			dev_dbg(dev, "no remote pad connected to crossbar input %u\n",
+				route->sink_pad);
+			continue;
+		}
+
+		remote_sd = media_entity_to_v4l2_subdev(remote_pad->entity);
+		if (!remote_sd) {
+			dev_err(dev, "no subdev connected to crossbar input %u\n",
+				route->sink_pad);
+			ret = -EPIPE;
+			goto out_unlock;
+		}
+
+		/* Get frame descriptor from the remote subdev */
+		ret = v4l2_subdev_call(remote_sd, pad, get_frame_desc,
+				       remote_pad->index, &source_fd);
+		if (ret == -ENOIOCTLCMD) {
+			dev_dbg(dev, "%s:%u does not support frame descriptors\n",
+				remote_sd->entity.name, remote_pad->index);
+			continue;
+		}
+		if (ret < 0) {
+			dev_err(dev, "failed to get frame desc from %s:%u: %u\n",
+				remote_sd->entity.name, remote_pad->index, ret);
+			goto out_unlock;
+		}
+
+		if (fd->num_entries == 0)
+			fd->type = source_fd.type;
+
+		/* Find the source frame descriptor entry matching the sink stream */
+		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(dev, "stream %u not found in frame desc from %s:%u\n",
+				route->sink_stream, remote_sd->entity.name,
+				remote_pad->index);
+			ret = -EPIPE;
+			goto out_unlock;
+		}
+
+		if (fd->num_entries >= ARRAY_SIZE(fd->entry)) {
+			dev_err(dev, "frame descriptor is full\n");
+			ret = -ENOSPC;
+			goto out_unlock;
+		}
+
+		/* Copy the entry and update the stream ID */
+		fd->entry[fd->num_entries] = source_fd.entry[i];
+		fd->entry[fd->num_entries].stream = route->source_stream;
+		fd->num_entries++;
+	}
+
+out_unlock:
+	v4l2_subdev_unlock_state(state);
+
+	return ret;
+}
+
 static int mxc_isi_crossbar_set_routing(struct v4l2_subdev *sd,
 					struct v4l2_subdev_state *state,
 					enum v4l2_subdev_format_whence which,
@@ -404,6 +500,7 @@ static const struct v4l2_subdev_pad_ops mxc_isi_crossbar_subdev_pad_ops = {
 	.enum_mbus_code = mxc_isi_crossbar_enum_mbus_code,
 	.get_fmt = v4l2_subdev_get_fmt,
 	.set_fmt = mxc_isi_crossbar_set_fmt,
+	.get_frame_desc = mxc_isi_get_frame_desc,
 	.set_routing = mxc_isi_crossbar_set_routing,
 	.enable_streams = mxc_isi_crossbar_enable_streams,
 	.disable_streams = mxc_isi_crossbar_disable_streams,

-- 
2.34.1