[PATCH RESEND v2 20/32] drm/vkms: Introduce configfs for plane zpos property

Louis Chauvet
2025-10-29T14:37:27Z

Modern compositor rely on zpos management to offload some processing to
deticated hardware. In order to test multiple configurations, add zpos
configuration to configFS.

Introduce multiple attributes to configure zpos:
- zpos_enabled - Create or not the zpos property. If not created, the zpos
is undefined.
- zpos_mutable - If the zpos property is created, allow or not the
userspace to modify it
- zpos_initial - Initial value for zpos property. Must be between zpos_min
and zpos_max
- zpos_min - Minimal zpos value for this plane. Must be smaller than or
equals to zpos_max
- zpos_max - Maximal zpos value for this plane. Must be greater than or
equals to zpos_min

Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>
---
Documentation/gpu/vkms.rst | 9 +-
drivers/gpu/drm/vkms/vkms_configfs.c | 180 +++++++++++++++++++++++++++++++++++
2 files changed, 188 insertions(+), 1 deletion(-)

diff --git a/Documentation/gpu/vkms.rst b/Documentation/gpu/vkms.rst
index 779ae363110d..32858f9a3357 100644
--- a/Documentation/gpu/vkms.rst
+++ b/Documentation/gpu/vkms.rst
@@ -87,7 +87,7 @@ Start by creating one or more planes::

sudo mkdir /config/vkms/my-vkms/planes/plane0

-Planes have 9 configurable attributes:
+Planes have 14 configurable attributes:

- type: Plane type: 0 overlay, 1 primary, 2 cursor (same values as those
exposed by the "type" property of a plane)
@@ -114,6 +114,13 @@ Planes have 9 configurable attributes:
To remove a format, use a minus and its fourcc: -XR24
To add all formats use +*
To remove all formats, use -*
+- zpos_enabled: Enable or not the zpos property: 1 enable, 0 disable
+- zpos_mutable: Create the zpos property as a mutable or imutable property: 1 mutable,
+ 0 disable. No effect if zpos_enabled is not set.
+- zpos_initial: Set the initial zpos value. Must be between zpos_min and zpos_max. No
+ effect if zpos_enabled is not set.
+- zpos_min: Set the minimal zpos value. No effect if zpos_enabled is not set.
+- zpos_max: Set the maximal zpos value. No effect if zpos_enabled is not set.

Continue by creating one or more CRTCs::

diff --git a/drivers/gpu/drm/vkms/vkms_configfs.c b/drivers/gpu/drm/vkms/vkms_configfs.c
index b0a26c4dbebe..1c0a6ecf2f29 100644
--- a/drivers/gpu/drm/vkms/vkms_configfs.c
+++ b/drivers/gpu/drm/vkms/vkms_configfs.c
@@ -735,6 +735,176 @@ static ssize_t plane_supported_formats_store(struct config_item *item,
return count;
}

+static ssize_t plane_zpos_enabled_show(struct config_item *item, char *page)
+{
+ struct vkms_configfs_plane *plane;
+ bool enabled;
+
+ plane = plane_item_to_vkms_configfs_plane(item);
+
+ scoped_guard(mutex, &plane->dev->lock)
+ enabled = vkms_config_plane_get_zpos_enabled(plane->config);
+
+ return sprintf(page, "%d\n", enabled);
+}
+
+static ssize_t plane_zpos_enabled_store(struct config_item *item, const char *page,
+ size_t count)
+{
+ struct vkms_configfs_plane *plane;
+ bool enabled;
+
+ plane = plane_item_to_vkms_configfs_plane(item);
+
+ if (kstrtobool(page, &enabled))
+ return -EINVAL;
+
+ scoped_guard(mutex, &plane->dev->lock) {
+ if (plane->dev->enabled)
+ return -EBUSY;
+
+ vkms_config_plane_set_zpos_enabled(plane->config, enabled);
+ }
+
+ return (ssize_t)count;
+}
+
+static ssize_t plane_zpos_mutable_show(struct config_item *item, char *page)
+{
+ struct vkms_configfs_plane *plane;
+ bool mutable;
+
+ plane = plane_item_to_vkms_configfs_plane(item);
+
+ scoped_guard(mutex, &plane->dev->lock)
+ mutable = vkms_config_plane_get_zpos_mutable(plane->config);
+
+ return sprintf(page, "%d\n", mutable);
+}
+
+static ssize_t plane_zpos_mutable_store(struct config_item *item, const char *page,
+ size_t count)
+{
+ struct vkms_configfs_plane *plane;
+ bool mutable;
+
+ plane = plane_item_to_vkms_configfs_plane(item);
+
+ if (kstrtobool(page, &mutable))
+ return -EINVAL;
+
+ scoped_guard(mutex, &plane->dev->lock) {
+ if (plane->dev->enabled)
+ return -EBUSY;
+
+ vkms_config_plane_set_zpos_mutable(plane->config, mutable);
+ }
+
+ return (ssize_t)count;
+}
+
+static ssize_t plane_zpos_initial_show(struct config_item *item, char *page)
+{
+ struct vkms_configfs_plane *plane;
+ unsigned int initial;
+
+ plane = plane_item_to_vkms_configfs_plane(item);
+
+ scoped_guard(mutex, &plane->dev->lock)
+ initial = vkms_config_plane_get_zpos_initial(plane->config);
+
+ return sprintf(page, "%u\n", initial);
+}
+
+static ssize_t plane_zpos_initial_store(struct config_item *item, const char *page,
+ size_t count)
+{
+ struct vkms_configfs_plane *plane;
+ unsigned int initial;
+
+ plane = plane_item_to_vkms_configfs_plane(item);
+
+ if (kstrtouint(page, 10, &initial))
+ return -EINVAL;
+
+ scoped_guard(mutex, &plane->dev->lock) {
+ if (plane->dev->enabled)
+ return -EBUSY;
+
+ vkms_config_plane_set_zpos_initial(plane->config, initial);
+ }
+
+ return (ssize_t)count;
+}
+
+static ssize_t plane_zpos_min_show(struct config_item *item, char *page)
+{
+ struct vkms_configfs_plane *plane;
+ unsigned int min;
+
+ plane = plane_item_to_vkms_configfs_plane(item);
+
+ scoped_guard(mutex, &plane->dev->lock)
+ min = vkms_config_plane_get_zpos_min(plane->config);
+
+ return sprintf(page, "%u\n", min);
+}
+
+static ssize_t plane_zpos_min_store(struct config_item *item, const char *page,
+ size_t count)
+{
+ struct vkms_configfs_plane *plane;
+ unsigned int min;
+
+ plane = plane_item_to_vkms_configfs_plane(item);
+
+ if (kstrtouint(page, 10, &min))
+ return -EINVAL;
+
+ scoped_guard(mutex, &plane->dev->lock) {
+ if (plane->dev->enabled)
+ return -EBUSY;
+
+ vkms_config_plane_set_zpos_min(plane->config, min);
+ }
+
+ return (ssize_t)count;
+}
+
+static ssize_t plane_zpos_max_show(struct config_item *item, char *page)
+{
+ struct vkms_configfs_plane *plane;
+ unsigned int max;
+
+ plane = plane_item_to_vkms_configfs_plane(item);
+
+ scoped_guard(mutex, &plane->dev->lock)
+ max = vkms_config_plane_get_zpos_max(plane->config);
+
+ return sprintf(page, "%u\n", max);
+}
+
+static ssize_t plane_zpos_max_store(struct config_item *item, const char *page,
+ size_t count)
+{
+ struct vkms_configfs_plane *plane;
+ unsigned int max;
+
+ plane = plane_item_to_vkms_configfs_plane(item);
+
+ if (kstrtouint(page, 10, &max))
+ return -EINVAL;
+
+ scoped_guard(mutex, &plane->dev->lock) {
+ if (plane->dev->enabled)
+ return -EBUSY;
+
+ vkms_config_plane_set_zpos_max(plane->config, max);
+ }
+
+ return (ssize_t)count;
+}
+
CONFIGFS_ATTR(plane_, type);
CONFIGFS_ATTR(plane_, name);
CONFIGFS_ATTR(plane_, supported_rotations);
@@ -744,6 +914,11 @@ CONFIGFS_ATTR(plane_, default_color_range);
CONFIGFS_ATTR(plane_, supported_color_encodings);
CONFIGFS_ATTR(plane_, default_color_encoding);
CONFIGFS_ATTR(plane_, supported_formats);
+CONFIGFS_ATTR(plane_, zpos_enabled);
+CONFIGFS_ATTR(plane_, zpos_mutable);
+CONFIGFS_ATTR(plane_, zpos_initial);
+CONFIGFS_ATTR(plane_, zpos_min);
+CONFIGFS_ATTR(plane_, zpos_max);

static struct configfs_attribute *plane_item_attrs[] = {
&plane_attr_type,
@@ -755,6 +930,11 @@ static struct configfs_attribute *plane_item_attrs[] = {
&plane_attr_supported_color_encodings,
&plane_attr_default_color_encoding,
&plane_attr_supported_formats,
+ &plane_attr_zpos_enabled,
+ &plane_attr_zpos_mutable,
+ &plane_attr_zpos_initial,
+ &plane_attr_zpos_min,
+ &plane_attr_zpos_max,
NULL,
};

--
2.51.0