[03/16] drm/vkms: Allow to configure multiple planes via configfs

Commit Message

José Expósito Feb. 18, 2025, 5:07 p.m. UTC

Create a default subgroup at /config/vkms/planes to allow to create as
many planes as required.

Co-developed-by: Louis Chauvet <[e-mail]>
Signed-off-by: Louis Chauvet <[e-mail]>
Signed-off-by: José Expósito <[e-mail]>
---
 Documentation/gpu/vkms.rst           |  16 ++++-
 drivers/gpu/drm/vkms/vkms_configfs.c | 101 +++++++++++++++++++++++++++
 2 files changed, 116 insertions(+), 1 deletion(-)

Patch

diff --git a/Documentation/gpu/vkms.rst b/Documentation/gpu/vkms.rst
index 423bdf86b5b1..bf23d0da33fe 100644
--- a/Documentation/gpu/vkms.rst
+++ b/Documentation/gpu/vkms.rst
@@ -71,6 +71,19 @@  By default, the instance is disabled::
   cat /config/vkms/my-vkms/enabled
   0
 
+And directories are created for each configurable item of the display pipeline::
+
+  tree /config/vkms/my-vkms
+  ├── enabled
+  └── planes
+
+To add items to the display pipeline, create one or more directories under the
+available paths.
+
+Start by creating one or more planes::
+
+  sudo mkdir /config/vkms/my-vkms/planes/plane0
+
 Once you are done configuring the VKMS instance, enable it::
 
   echo "1" | sudo tee /config/vkms/my-vkms/enabled
@@ -79,8 +92,9 @@  Finally, you can remove the VKMS instance disabling it::
 
   echo "0" | sudo tee /config/vkms/my-vkms/enabled
 
-And removing the top level directory::
+And removing the top level directory and its subdirectories::
 
+  sudo rmdir /config/vkms/my-vkms/planes/*
   sudo rmdir /config/vkms/my-vkms
 
 Testing With IGT
diff --git a/drivers/gpu/drm/vkms/vkms_configfs.c b/drivers/gpu/drm/vkms/vkms_configfs.c
index 306f571559b7..dd9dfe51eb3a 100644
--- a/drivers/gpu/drm/vkms/vkms_configfs.c
+++ b/drivers/gpu/drm/vkms/vkms_configfs.c
@@ -15,6 +15,7 @@  static bool is_configfs_registered;
  *
  * @group: Top level configuration group that represents a VKMS device.
  * Initialized when a new directory is created under "/config/vkms/"
+ * @planes_group: Default subgroup of @group at "/config/vkms/planes"
  * @lock: Lock used to project concurrent access to the configuration attributes
  * @config: Protected by @lock. Configuration of the VKMS device
  * @enabled: Protected by @lock. The device is created or destroyed when this
@@ -22,16 +23,112 @@  static bool is_configfs_registered;
  */
 struct vkms_configfs_device {
 	struct config_group group;
+	struct config_group planes_group;
 
 	struct mutex lock;
 	struct vkms_config *config;
 	bool enabled;
 };
 
+/**
+ * struct vkms_configfs_plane - Configfs representation of a plane
+ *
+ * @group: Top level configuration group that represents a plane.
+ * Initialized when a new directory is created under "/config/vkms/planes"
+ * @dev: The vkms_configfs_device this plane belongs to
+ * @config: Configuration of the VKMS plane
+ */
+struct vkms_configfs_plane {
+	struct config_group group;
+	struct vkms_configfs_device *dev;
+	struct vkms_config_plane *config;
+};
+
 #define device_item_to_vkms_configfs_device(item) \
 	container_of(to_config_group((item)), struct vkms_configfs_device, \
 		     group)
 
+#define child_group_to_vkms_configfs_device(group) \
+	device_item_to_vkms_configfs_device((&(group)->cg_item)->ci_parent)
+
+#define plane_item_to_vkms_configfs_plane(item) \
+	container_of(to_config_group((item)), struct vkms_configfs_plane, group)
+
+static void plane_release(struct config_item *item)
+{
+	struct vkms_configfs_plane *plane;
+	struct mutex *lock;
+
+	plane = plane_item_to_vkms_configfs_plane(item);
+	lock = &plane->dev->lock;
+
+	mutex_lock(lock);
+	vkms_config_destroy_plane(plane->config);
+	kfree(plane);
+	mutex_unlock(lock);
+}
+
+static struct configfs_item_operations plane_item_operations = {
+	.release	= &plane_release,
+};
+
+static const struct config_item_type plane_item_type = {
+	.ct_item_ops	= &plane_item_operations,
+	.ct_owner	= THIS_MODULE,
+};
+
+static struct config_group *make_plane_group(struct config_group *group,
+					     const char *name)
+{
+	struct vkms_configfs_device *dev;
+	struct vkms_configfs_plane *plane;
+	int ret;
+
+	dev = child_group_to_vkms_configfs_device(group);
+
+	mutex_lock(&dev->lock);
+
+	if (dev->enabled) {
+		ret = -EINVAL;
+		goto err_unlock;
+	}
+
+	plane = kzalloc(sizeof(*plane), GFP_KERNEL);
+	if (!plane) {
+		ret = -ENOMEM;
+		goto err_unlock;
+	}
+
+	plane->dev = dev;
+
+	plane->config = vkms_config_create_plane(dev->config);
+	if (IS_ERR(plane->config)) {
+		ret = PTR_ERR(plane->config);
+		goto err_free;
+	}
+
+	config_group_init_type_name(&plane->group, name, &plane_item_type);
+
+	mutex_unlock(&dev->lock);
+
+	return &plane->group;
+
+err_free:
+	kfree(plane);
+err_unlock:
+	mutex_unlock(&dev->lock);
+	return ERR_PTR(ret);
+}
+
+static struct configfs_group_operations planes_group_operations = {
+	.make_group	= &make_plane_group,
+};
+
+static const struct config_item_type plane_group_type = {
+	.ct_group_ops	= &planes_group_operations,
+	.ct_owner	= THIS_MODULE,
+};
+
 static ssize_t device_enabled_show(struct config_item *item, char *page)
 {
 	struct vkms_configfs_device *dev;
@@ -137,6 +234,10 @@  static struct config_group *make_device_group(struct config_group *group,
 	config_group_init_type_name(&dev->group, name, &device_item_type);
 	mutex_init(&dev->lock);
 
+	config_group_init_type_name(&dev->planes_group, "planes",
+				    &plane_group_type);
+	configfs_add_default_group(&dev->planes_group, &dev->group);
+
 	return &dev->group;
 }