[PATCH RESEND v2 09/32] drm/vkms: Introduce configfs for plane rotation

Louis Chauvet
2025-10-29T14:37:07Z

To allows the userspace to test many hardware configuration, introduce a
new interface to configure the available rotation per planes. VKMS
supports any rotation and reflection, so the userspace can choose any
combination.

The supported rotations are configured by writing a rotation bitmask to
the file `supported_rotations` and the default rotation is chosen by
writing a rotation bitmask to `default_rotation`.

Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>
---
Documentation/gpu/vkms.rst | 7 ++-
drivers/gpu/drm/vkms/vkms_configfs.c | 91 ++++++++++++++++++++++++++++++++++++
2 files changed, 97 insertions(+), 1 deletion(-)

diff --git a/Documentation/gpu/vkms.rst b/Documentation/gpu/vkms.rst
index 1fe6e420c963..eac1a942d6c4 100644
--- a/Documentation/gpu/vkms.rst
+++ b/Documentation/gpu/vkms.rst
@@ -87,11 +87,16 @@ Start by creating one or more planes::

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

-Planes have 2 configurable attributes:
+Planes have 4 configurable attributes:

- type: Plane type: 0 overlay, 1 primary, 2 cursor (same values as those
exposed by the "type" property of a plane)
- name: Name of the plane
+- possible_rotations: Available rotation for a plane, as a bitmask: 0x01 no rotation,
+ 0x02 rotate 90°, 0x04 rotate 180°, 0x08 rotate 270°, 0x10 reflect x, 0x20 reflect y
+ (same values as those exposed by the "rotation" property of a plane)
+- default_rotation: Default rotation presented to the userspace, same values as
+ possible_rotations.

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 be6c3ba998b9..7cc8ba315ef0 100644
--- a/drivers/gpu/drm/vkms/vkms_configfs.c
+++ b/drivers/gpu/drm/vkms/vkms_configfs.c
@@ -352,12 +352,103 @@ static ssize_t plane_name_store(struct config_item *item, const char *page,
return (ssize_t)count;
}

+static ssize_t plane_supported_rotations_show(struct config_item *item, char *page)
+{
+ struct vkms_configfs_plane *plane;
+ unsigned int plane_supported_rotations;
+
+ plane = plane_item_to_vkms_configfs_plane(item);
+
+ scoped_guard(mutex, &plane->dev->lock) {
+ plane_supported_rotations = vkms_config_plane_get_supported_rotations(plane->config);
+ }
+
+ return sprintf(page, "%u", plane_supported_rotations);
+}
+
+static ssize_t plane_supported_rotations_store(struct config_item *item,
+ const char *page, size_t count)
+{
+ struct vkms_configfs_plane *plane = plane_item_to_vkms_configfs_plane(item);
+ int ret, val = 0;
+
+ ret = kstrtouint(page, 0, &val);
+ if (ret)
+ return ret;
+
+ /* Should be a supported value */
+ if (val & ~(DRM_MODE_ROTATE_MASK | DRM_MODE_REFLECT_MASK))
+ return -EINVAL;
+ /* Should at least provide one rotation */
+ if (!(val & DRM_MODE_ROTATE_MASK))
+ return -EINVAL;
+
+ scoped_guard(mutex, &plane->dev->lock) {
+ /* Ensures that the default rotation is included in supported rotation */
+ if (plane->dev->enabled)
+ return -EINVAL;
+
+ vkms_config_plane_set_supported_rotations(plane->config, val);
+ }
+
+ return count;
+}
+
+static ssize_t plane_default_rotation_show(struct config_item *item, char *page)
+{
+ struct vkms_configfs_plane *plane;
+ unsigned int plane_default_rotation;
+
+ plane = plane_item_to_vkms_configfs_plane(item);
+
+ scoped_guard(mutex, &plane->dev->lock) {
+ plane_default_rotation = vkms_config_plane_get_default_rotation(plane->config);
+ }
+
+ return sprintf(page, "%u", plane_default_rotation);
+}
+
+static ssize_t plane_default_rotation_store(struct config_item *item,
+ const char *page, size_t count)
+{
+ struct vkms_configfs_plane *plane = plane_item_to_vkms_configfs_plane(item);
+ int ret, val = 0;
+
+ ret = kstrtouint(page, 10, &val);
+ if (ret)
+ return ret;
+
+ /* Should be a supported value */
+ if (val & ~(DRM_MODE_ROTATE_MASK | DRM_MODE_REFLECT_MASK))
+ return -EINVAL;
+ /* Should at least provide one rotation */
+ if ((val & DRM_MODE_ROTATE_MASK) == 0)
+ return -EINVAL;
+ /* Should contains only one rotation */
+ if (!is_power_of_2(val & DRM_MODE_ROTATE_MASK))
+ return -EINVAL;
+
+ scoped_guard(mutex, &plane->dev->lock) {
+ /* Ensures that the default rotation is included in supported rotation */
+ if (plane->dev->enabled)
+ return -EINVAL;
+
+ vkms_config_plane_set_default_rotation(plane->config, val);
+ }
+
+ return count;
+}
+
CONFIGFS_ATTR(plane_, type);
CONFIGFS_ATTR(plane_, name);
+CONFIGFS_ATTR(plane_, supported_rotations);
+CONFIGFS_ATTR(plane_, default_rotation);

static struct configfs_attribute *plane_item_attrs[] = {
&plane_attr_type,
&plane_attr_name,
+ &plane_attr_supported_rotations,
+ &plane_attr_default_rotation,
NULL,
};

--
2.51.0