[PATCH 15/26] media: v4l2_subdev: Introduce default context

[Jacopo Mondi]

Introduce a default context for v4l2 subdvice.

Drivers ported to use multi-context support that used to work with a
non-context aware userspace (which doesn't call VIDIOC_SUBDEV_BIND_CONTEXT)
shall continue to work even if they are context aware.

Provide a default context in the v4l2 subdev and bind it to the media
device default context when the subdevice is fully registered by
providing a v4l2_subdev_registered() function.

Release the context when the subdevice gets unregistered by the core,
providing a v4l2_subdev_unregistered() helper.

Signed-off-by: Jacopo Mondi <jacopo.mondi at ideasonboard.com>
---
 drivers/media/v4l2-core/v4l2-device.c | 11 +++-----
 drivers/media/v4l2-core/v4l2-subdev.c | 50 +++++++++++++++++++++++++++++++++++
 include/media/v4l2-subdev.h           | 29 ++++++++++++++++++++
 3 files changed, 83 insertions(+), 7 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-device.c b/drivers/media/v4l2-core/v4l2-device.c
index 5e537454f5cd71b3c50a2a2864642f7d5548047b..bf3ebd77b7bb8b13c849a89d01e6d889e8a2e4fd 100644
--- a/drivers/media/v4l2-core/v4l2-device.c
+++ b/drivers/media/v4l2-core/v4l2-device.c
@@ -146,11 +146,9 @@ int __v4l2_device_register_subdev(struct v4l2_device *v4l2_dev,
 	}
 #endif
 
-	if (sd->internal_ops && sd->internal_ops->registered) {
-		err = sd->internal_ops->registered(sd);
-		if (err)
-			goto error_unregister;
-	}
+	err = v4l2_subdev_registered(sd);
+	if (err)
+		goto error_unregister;
 
 	sd->owner = module;
 
@@ -274,8 +272,7 @@ void v4l2_device_unregister_subdev(struct v4l2_subdev *sd)
 	list_del(&sd->list);
 	spin_unlock(&v4l2_dev->lock);
 
-	if (sd->internal_ops && sd->internal_ops->unregistered)
-		sd->internal_ops->unregistered(sd);
+	v4l2_subdev_unregistered(sd);
 	sd->v4l2_dev = NULL;
 
 #if defined(CONFIG_MEDIA_CONTROLLER)
diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index 300f84317623dd082a4cd2caec97057f972e82a3..438f51980e5ac0f092ba6b0a979a376133968ddf 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -1275,6 +1275,56 @@ const struct v4l2_file_operations v4l2_subdev_fops = {
 	.poll = subdev_poll,
 };
 
+#ifdef CONFIG_MEDIA_CONTROLLER
+static int v4l2_subdev_register_default_context(struct v4l2_subdev *sd)
+{
+	struct media_device_context *mdev_context;
+
+	/* If the driver does not support contexts, return here. */
+	if (!sd->entity.ops || !sd->entity.ops->alloc_context ||
+	    !sd->entity.ops->destroy_context)
+		return 0;
+
+	mdev_context = sd->entity.graph_obj.mdev->default_context;
+	return subdev_do_bind_context(sd, &sd->default_context, mdev_context);
+}
+#endif /* CONFIG_MEDIA_CONTROLLER */
+
+int v4l2_subdev_registered(struct v4l2_subdev *sd)
+{
+	int ret;
+
+#ifdef CONFIG_MEDIA_CONTROLLER
+	ret = v4l2_subdev_register_default_context(sd);
+	if (ret)
+		return ret;
+#endif /* CONFIG_MEDIA_CONTROLLER */
+
+	if (sd->internal_ops && sd->internal_ops->registered) {
+		ret = sd->internal_ops->registered(sd);
+		if (ret)
+			goto err_registered;
+	}
+
+	return 0;
+
+err_registered:
+	if (sd->default_context)
+		v4l2_subdev_context_put(sd->default_context);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(v4l2_subdev_registered);
+
+void v4l2_subdev_unregistered(struct v4l2_subdev *sd)
+{
+	if (sd->default_context)
+		v4l2_subdev_context_put(sd->default_context);
+
+	if (sd->internal_ops && sd->internal_ops->unregistered)
+		sd->internal_ops->unregistered(sd);
+}
+EXPORT_SYMBOL_GPL(v4l2_subdev_unregistered);
+
 #ifdef CONFIG_MEDIA_CONTROLLER
 
 int v4l2_subdev_get_fwnode_pad_1_to_1(struct media_entity *entity,
diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index 9d257b859acafb11cfe6976e906e7baabd0206f6..1fa42a9f322be0be44fc9308744f4f4ae0cf1606 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -1130,6 +1130,10 @@ struct v4l2_subdev_platform_data {
  * @active_state: Active state for the subdev (NULL for subdevs tracking the
  *		  state internally). Initialized by calling
  *		  v4l2_subdev_init_finalize().
+ * @default_context: Default context for the subdev, allows to operate
+ *		     context-aware drivers with a context-unaware userspace.
+ *		     It is initialized when the subdev is registered in
+ *		     v4l2_subdev_registered().
  * @enabled_pads: Bitmask of enabled pads used by v4l2_subdev_enable_streams()
  *		  and v4l2_subdev_disable_streams() helper functions for
  *		  fallback cases.
@@ -1182,6 +1186,7 @@ struct v4l2_subdev {
 	 * doesn't support it.
 	 */
 	struct v4l2_subdev_state *active_state;
+	struct v4l2_subdev_context *default_context;
 	u64 enabled_pads;
 	bool s_stream_enabled;
 };
@@ -1286,6 +1291,30 @@ static inline void *v4l2_get_subdev_hostdata(const struct v4l2_subdev *sd)
 	return sd->host_priv;
 }
 
+/**
+ * v4l2_subdev_registered - Subdevice registered notification
+ *
+ * @sd: The subdevice that has been registered
+ *
+ * Notify that a subdevice has been registered by the core. This function wraps
+ * a call to sd->internal_ops->registered (if available) and instantiates the
+ * default v4l2 subdevice context.
+ *
+ * Returns 0 on success, a negative error code otherwise.
+ */
+int v4l2_subdev_registered(struct v4l2_subdev *sd);
+
+/**
+ * v4l2_subdev_unregistered - Subdevice unregistered notification
+ *
+ * @sd: The subdevice that has been unregistered
+ *
+ * Notify that a subdevice has been unregistered by the core. This function
+ * wraps a call to sd->internal_ops->unregistered (if available) and deletes
+ * the default v4l2 subdevice context.
+ */
+void v4l2_subdev_unregistered(struct v4l2_subdev *sd);
+
 #ifdef CONFIG_MEDIA_CONTROLLER
 
 /**

-- 
2.49.0