[PATCH v4 16/37] drm/vkms: Introduce configfs for plane rotation

[Louis Chauvet <louis.chauvet@bootlin.com>]

To allows the userspace to test many hardware configurations, 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/ABI/testing/configfs-vkms | 15 ++++++
 Documentation/gpu/vkms.rst              |  7 ++-
 drivers/gpu/drm/vkms/vkms_configfs.c    | 82 +++++++++++++++++++++++++++++++++
 3 files changed, 103 insertions(+), 1 deletion(-)

diff --git a/Documentation/ABI/testing/configfs-vkms b/Documentation/ABI/testing/configfs-vkms
index 642d0dad8cca..55472f4e721d 100644
--- a/Documentation/ABI/testing/configfs-vkms
+++ b/Documentation/ABI/testing/configfs-vkms
@@ -109,6 +109,21 @@ Contact:	dri-devel@lists.freedesktop.org
 Description:
 	Name of the plane.
 
+What:		/sys/kernel/config/vkms/<device>/planes/<plane>/supported_rotations
+Date:		Nov 2025
+Contact:	dri-devel@lists.freedesktop.org
+Description:
+	Available rotations for the plane, as a bitmask:
+	0x01 - no rotation, 0x02 - rotate 90°, 0x04 - rotate 180°,
+	0x08 - rotate 270°, 0x10 - reflect x, 0x20 - reflect y.
+
+What:		/sys/kernel/config/vkms/<device>/planes/<plane>/default_rotation
+Date:		Nov 2025
+Contact:	dri-devel@lists.freedesktop.org
+Description:
+	Default rotation presented to userspace, same values as
+	possible_rotations.
+
 What:		/sys/kernel/config/vkms/<device>/planes/<plane>/possible_crtcs
 Date:		Nov 2025
 Contact:	dri-devel@lists.freedesktop.org
diff --git a/Documentation/gpu/vkms.rst b/Documentation/gpu/vkms.rst
index 79f1185d8645..034565eb43ad 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. Allowed characters are [A-Za-z1-9_-]
+- supported_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
+  supported_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 e8d5792b0873..5ed6a7fa6046 100644
--- a/drivers/gpu/drm/vkms/vkms_configfs.c
+++ b/drivers/gpu/drm/vkms/vkms_configfs.c
@@ -384,12 +384,94 @@ 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 = plane_item_to_vkms_configfs_plane(item);
+	unsigned int plane_supported_rotations;
+
+	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) {
+		if (plane->dev->enabled)
+			return -EBUSY;
+
+		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 = plane_item_to_vkms_configfs_plane(item);
+	unsigned int plane_default_rotation;
+
+	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 contain exactly one rotation */
+	if (!is_power_of_2(val & DRM_MODE_ROTATE_MASK))
+		return -EINVAL;
+
+	scoped_guard(mutex, &plane->dev->lock) {
+		if (plane->dev->enabled)
+			return -EBUSY;
+
+		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,
 };
 

-- 
2.54.0