[PATCH v4 20/37] drm/vkms: Introduce configfs for plane color range

Louis Chauvet
2026-04-22T16:49:47Z

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

The supported color ranges are configured by writing a color range bitmask
to the file `supported_color_ranges` and the default color range is
chosen by writing a color encoding bitmask to `default_color_range`.

Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>
---
Documentation/ABI/testing/configfs-vkms | 15 ++++++
Documentation/gpu/vkms.rst | 10 +++-
drivers/gpu/drm/vkms/vkms_configfs.c | 90 +++++++++++++++++++++++++++++++++
3 files changed, 113 insertions(+), 2 deletions(-)

diff --git a/Documentation/ABI/testing/configfs-vkms b/Documentation/ABI/testing/configfs-vkms
index 836169910884..97681108af1c 100644
--- a/Documentation/ABI/testing/configfs-vkms
+++ b/Documentation/ABI/testing/configfs-vkms
@@ -138,6 +138,21 @@ Description:
Default color encoding presented to userspace, same
values as supported_color_encoding.

+What: /sys/kernel/config/vkms/<device>/planes/<plane>/supported_color_ranges
+Date: Nov 2025
+Contact: dri-devel@lists.freedesktop.org
+Description:
+ Available color ranges for the plane, as a bitmask:
+ 0x1 - DRM_COLOR_YCBCR_LIMITED_RANGE,
+ 0x2 - DRM_COLOR_YCBCR_FULL_RANGE.
+
+What: /sys/kernel/config/vkms/<device>/planes/<plane>/default_color_range
+Date: Nov 2025
+Contact: dri-devel@lists.freedesktop.org
+Description:
+ Default color range presented to userspace, same
+ values as supported_color_ranges.
+
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 4b3dfbe4e13a..8ba0b0353376 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 6 configurable attributes:
+Planes have 8 configurable attributes:

- type: Plane type: 0 overlay, 1 primary, 2 cursor (same values as those
exposed by the "type" property of a plane)
@@ -99,10 +99,16 @@ Planes have 6 configurable attributes:
supported_rotations.
- supported_color_encodings: Available encodings for a plane, as a bitmask:
0x01 YCBCR_BT601, 0x02 YCBCR_BT709, 0x04 YCBCR_BT2020 (same values as those exposed
- by the COLOR_ENCODING property of a plane). If set, supported_color_range
+ by the COLOR_ENCODING property of a plane). If set, supported_color_ranges
must be set too.
- default_color_encoding: Default color encoding presented to the userspace, same
values as supported_color_encodings
+- supported_color_ranges: Available color range for a plane, as a bitmask:
+ 0x1 DRM_COLOR_YCBCR_LIMITED_RANGE, 0x2 DRM_COLOR_YCBCR_FULL_RANGE (same values as
+ those exposed by the COLOR_RANGE property of a plane). If set, supported_color_encoding
+ must be set too.
+- default_color_range: Default color range presented to the userspace, same
+ values as supported_color_ranges

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 a5174fc8321c..855b1d5f5d31 100644
--- a/drivers/gpu/drm/vkms/vkms_configfs.c
+++ b/drivers/gpu/drm/vkms/vkms_configfs.c
@@ -17,6 +17,13 @@
BIT(DRM_COLOR_YCBCR_BT709) | \
BIT(DRM_COLOR_YCBCR_BT2020))

+/**
+ * VKMS_SUPPORTED_COLOR_RANGES - Bitmask of all supported color ranges in VKMS
+ */
+#define VKMS_SUPPORTED_COLOR_RANGES ( \
+ BIT(DRM_COLOR_YCBCR_LIMITED_RANGE) | \
+ BIT(DRM_COLOR_YCBCR_FULL_RANGE))
+
/* To avoid registering configfs more than once or unregistering on error */
static bool is_configfs_registered;

@@ -470,6 +477,85 @@ static ssize_t plane_default_rotation_store(struct config_item *item,
return count;
}

+static ssize_t plane_supported_color_ranges_show(struct config_item *item, char *page)
+{
+ struct vkms_configfs_plane *plane = plane_item_to_vkms_configfs_plane(item);
+ unsigned int supported_color_ranges;
+
+ scoped_guard(mutex, &plane->dev->lock)
+ supported_color_ranges = vkms_config_plane_get_supported_color_ranges(plane->config);
+
+ return sprintf(page, "%u", supported_color_ranges);
+}
+
+static ssize_t plane_supported_color_ranges_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 & ~VKMS_SUPPORTED_COLOR_RANGES)
+ return -EINVAL;
+ /* Should at least provide one color range */
+ if ((val & VKMS_SUPPORTED_COLOR_RANGES) == 0)
+ return -EINVAL;
+
+ scoped_guard(mutex, &plane->dev->lock) {
+ if (plane->dev->enabled)
+ return -EBUSY;
+
+ vkms_config_plane_set_supported_color_ranges(plane->config, val);
+ }
+
+ return count;
+}
+
+static ssize_t plane_default_color_range_show(struct config_item *item, char *page)
+{
+ struct vkms_configfs_plane *plane = plane_item_to_vkms_configfs_plane(item);
+ unsigned int default_color_range;
+
+ scoped_guard(mutex, &plane->dev->lock)
+ default_color_range = vkms_config_plane_get_default_color_range(plane->config);
+
+ return sprintf(page, "%lu", BIT(default_color_range));
+}
+
+static ssize_t plane_default_color_range_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 & ~VKMS_SUPPORTED_COLOR_RANGES)
+ return -EINVAL;
+
+ if (!is_power_of_2(val))
+ return -EINVAL;
+
+ /* Convert bit position to the proper enum value */
+ val = ffs(val) + DRM_COLOR_YCBCR_LIMITED_RANGE - 1;
+
+ scoped_guard(mutex, &plane->dev->lock) {
+ if (plane->dev->enabled)
+ return -EBUSY;
+
+ vkms_config_plane_set_default_color_range(plane->config, val);
+ }
+
+ return count;
+}
+
static ssize_t plane_supported_color_encodings_show(struct config_item *item, char *page)
{
struct vkms_configfs_plane *plane = plane_item_to_vkms_configfs_plane(item);
@@ -554,6 +640,8 @@ CONFIGFS_ATTR(plane_, type);
CONFIGFS_ATTR(plane_, name);
CONFIGFS_ATTR(plane_, supported_rotations);
CONFIGFS_ATTR(plane_, default_rotation);
+CONFIGFS_ATTR(plane_, supported_color_ranges);
+CONFIGFS_ATTR(plane_, default_color_range);
CONFIGFS_ATTR(plane_, supported_color_encodings);
CONFIGFS_ATTR(plane_, default_color_encoding);

@@ -562,6 +650,8 @@ static struct configfs_attribute *plane_item_attrs[] = {
&plane_attr_name,
&plane_attr_supported_rotations,
&plane_attr_default_rotation,
+ &plane_attr_supported_color_ranges,
+ &plane_attr_default_color_range,
&plane_attr_supported_color_encodings,
&plane_attr_default_color_encoding,
NULL,

--
2.54.0