Re: [PATCH v6 18/24] v4l: subdev: Add [GS]_ROUTING subdev ioctls and operations

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On 29/04/2021 05:28, Laurent Pinchart wrote:
Hi Tomi,

Thank you for the patch.

For some reason, it seems the original authorship got lost. It was fine
in v5. I haven't checked if other patches in the series are affected.

On Tue, Apr 27, 2021 at 03:45:17PM +0300, Tomi Valkeinen wrote:
Add support for subdev internal routing. A route is defined as a single
stream from a sink pad to a source pad.

The userspace can configure the routing via two new ioctls,
VIDIOC_SUBDEV_G_ROUTING and VIDIOC_SUBDEV_S_ROUTING, and subdevs can
implement the functionality with v4l2_subdev_pad_ops.get_routing() and
v4l2_subdev_pad_ops.set_routing().

Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
Signed-off-by: Michal Simek <michal.simek@xxxxxxxxxx>

- Add sink and source streams for multiplexed links
- Copy the argument back in case of an error. This is needed to let the
   caller know the number of routes.

Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@xxxxxxxxxxxx>

- Expand and refine documentation.
- Make the 'routes' pointer a __u64 __user pointer so that a compat32
   version of the ioctl is not required.
- Add struct v4l2_subdev_krouting to be used for subdevice operations.

Signed-off-by: Jacopo Mondi <jacopo+renesas@xxxxxxxxxx>

- Fix typecasing warnings
- Check sink & source pad types
- Add 'which' field

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@xxxxxxxxxxxxxxxx>
---
  drivers/media/v4l2-core/v4l2-ioctl.c  | 25 +++++++++++++-
  drivers/media/v4l2-core/v4l2-subdev.c | 46 +++++++++++++++++++++++++
  include/media/v4l2-subdev.h           | 24 ++++++++++++++
  include/uapi/linux/v4l2-subdev.h      | 48 +++++++++++++++++++++++++++
  4 files changed, 142 insertions(+), 1 deletion(-)

diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
index 6a5d1c6d11d6..7b1dabc23909 100644
--- a/drivers/media/v4l2-core/v4l2-ioctl.c
+++ b/drivers/media/v4l2-core/v4l2-ioctl.c
@@ -16,6 +16,7 @@
  #include <linux/kernel.h>
  #include <linux/version.h>
+#include <linux/v4l2-subdev.h>
  #include <linux/videodev2.h>
#include <media/v4l2-common.h>
@@ -3108,6 +3109,21 @@ static int check_array_args(unsigned int cmd, void *parg, size_t *array_size,
  		ret = 1;
  		break;
  	}
+
+	case VIDIOC_SUBDEV_G_ROUTING:
+	case VIDIOC_SUBDEV_S_ROUTING: {
+		struct v4l2_subdev_routing *routing = parg;
+
+		if (routing->num_routes > 256)
+			return -EINVAL;
+
+		*user_ptr = u64_to_user_ptr(routing->routes);
+		*kernel_ptr = (void **)&routing->routes;
+		*array_size = sizeof(struct v4l2_subdev_route)
+			    * routing->num_routes;
+		ret = 1;
+		break;
+	}
  	}
return ret;
@@ -3369,8 +3385,15 @@ video_usercopy(struct file *file, unsigned int orig_cmd, unsigned long arg,
  	/*
  	 * Some ioctls can return an error, but still have valid
  	 * results that must be returned.
+	 *
+	 * FIXME: subdev IOCTLS are partially handled here and partially in
+	 * v4l2-subdev.c and the 'always_copy' flag can only be set for IOCTLS
+	 * defined here as part of the 'v4l2_ioctls' array. As
+	 * VIDIOC_SUBDEV_G_ROUTING needs to return results to applications even
+	 * in case of failure, but it is not defined here as part of the
+	 * 'v4l2_ioctls' array, insert an ad-hoc check to address that.
  	 */
-	if (err < 0 && !always_copy)
+	if (err < 0 && !always_copy && cmd != VIDIOC_SUBDEV_G_ROUTING)
  		goto out;
out_array_args:
diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index 956dafab43d4..ad79ce121cee 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -681,6 +681,52 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
  	case VIDIOC_SUBDEV_QUERYSTD:
  		return v4l2_subdev_call(sd, video, querystd, arg);
+ case VIDIOC_SUBDEV_G_ROUTING: {
+		struct v4l2_subdev_routing *routing = arg;
+		struct v4l2_subdev_krouting krouting = {
+			.which = routing->which,
+			.num_routes = routing->num_routes,
+			.routes = (struct v4l2_subdev_route *)(uintptr_t)
+					  routing->routes,
+		};
+		int ret;
+
+		ret = v4l2_subdev_call(sd, pad, get_routing, &krouting);
+
+		routing->num_routes = krouting.num_routes;
+
+		return ret;
+	}
+
+	case VIDIOC_SUBDEV_S_ROUTING: {
+		struct v4l2_subdev_routing *routing = arg;
+		struct v4l2_subdev_route *routes =
+			(struct v4l2_subdev_route *)(uintptr_t)routing->routes;
+		struct v4l2_subdev_krouting krouting = {};
+		unsigned int i;
+
+		if (routing->which != V4L2_SUBDEV_FORMAT_TRY && ro_subdev)
+			return -EPERM;
+
+		for (i = 0; i < routing->num_routes; ++i) {
+			if (routes[i].sink_pad >= sd->entity.num_pads ||
+			    routes[i].source_pad >= sd->entity.num_pads)
+				return -EINVAL;
+
+			if (!(sd->entity.pads[routes[i].sink_pad].flags &
+			      MEDIA_PAD_FL_SINK) ||
+			    !(sd->entity.pads[routes[i].source_pad].flags &
+			      MEDIA_PAD_FL_SOURCE))
+				return -EINVAL;
+		}
+
+		krouting.which = routing->which;
+		krouting.num_routes = routing->num_routes;
+		krouting.routes = routes;
+
+		return v4l2_subdev_call(sd, pad, set_routing, &krouting);
+	}
+
  	default:
  		return v4l2_subdev_call(sd, core, ioctl, cmd, arg);
  	}
diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index 70a21298020b..c45f5f0156c9 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -660,6 +660,22 @@ struct v4l2_subdev_pad_config {
  	struct v4l2_rect try_compose;
  };
+/**
+ * struct v4l2_subdev_krouting - subdev routing table
+ *
+ * @which: format type (from enum v4l2_subdev_format_whence)
+ * @routes: &struct v4l2_subdev_route
+ * @num_routes: number of routes
+ *
+ * This structure is used to translate arguments received from
+ * VIDIOC_SUBDEV_G/S_ROUTING() ioctl to subdev device drivers operations.
+ */
+struct v4l2_subdev_krouting {
+	u32 which;
+	struct v4l2_subdev_route *routes;
+	unsigned int num_routes;
+};
+
  /**
   * struct v4l2_subdev_pad_ops - v4l2-subdev pad level operations
   *
@@ -721,6 +737,10 @@ struct v4l2_subdev_pad_config {
   *		     applied to the hardware. The operation shall fail if the
   *		     pad index it has been called on is not valid or in case of
   *		     unrecoverable failures.
+ *
+ * @get_routing: get the subdevice routing table.
+ * @set_routing: enable or disable data connection routes described in the
+ *		 subdevice routing table.
   */
  struct v4l2_subdev_pad_ops {
  	int (*init_cfg)(struct v4l2_subdev *sd,
@@ -765,6 +785,10 @@ struct v4l2_subdev_pad_ops {
  			       struct v4l2_mbus_config *config);
  	int (*set_mbus_config)(struct v4l2_subdev *sd, unsigned int pad,
  			       struct v4l2_mbus_config *config);
+	int (*get_routing)(struct v4l2_subdev *sd,
+			   struct v4l2_subdev_krouting *route);
+	int (*set_routing)(struct v4l2_subdev *sd,
+			   struct v4l2_subdev_krouting *route);
  };
/**
diff --git a/include/uapi/linux/v4l2-subdev.h b/include/uapi/linux/v4l2-subdev.h
index 658106f5b5dc..3a360cdcacf4 100644
--- a/include/uapi/linux/v4l2-subdev.h
+++ b/include/uapi/linux/v4l2-subdev.h
@@ -188,6 +188,52 @@ struct v4l2_subdev_capability {
  /* The v4l2 sub-device video device node is registered in read-only mode. */
  #define V4L2_SUBDEV_CAP_RO_SUBDEV		0x00000001
+/*

Shouldn't this be /** ?

+ * Is the route active? An active route will start when streaming is enabled
+ * on a video node.

Even with an a priori knowledge of the topic, I'm not sure to really
understand this, and I don't think it reflects the purpose of the flag.

+ */
+#define V4L2_SUBDEV_ROUTE_FL_ACTIVE		BIT(0)
+
+/*
+ * Is the route immutable, i.e. can it be activated and inactivated?

Maybe adding "An immutable route is always active".

Is it? I was thinking that immutable could be used as a way to have a static routing table, but the routes could still be enabled and disables. Say, a sensor could have pixel and metadata streams. They would be immutable, you can't remove them, change them or add any other streams. But you could still enable/disable them.

But the doc doesn't convey this. And I think we would still need a way to describe what you mentioned, a route that's always there and enabled.

 Tomi



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