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    | 93 +++++++++++++++++++++++++++++++++
 3 files changed, 116 insertions(+), 2 deletions(-)

diff --git a/Documentation/ABI/testing/configfs-vkms b/Documentation/ABI/testing/configfs-vkms
index 242aae91289c..2ace79ce848a 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 0d4dae3ba8e5..ab0eb2f97fc2 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:
   possible_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 755978b17c95..7be6d10b2b68 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;
 
@@ -454,6 +461,88 @@ 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, "%u", 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;
+	/* Should at least provide one color range */
+	if ((val & VKMS_SUPPORTED_COLOR_RANGES) == 0)
+		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;
+
+	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);
@@ -543,6 +632,8 @@ 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);
 
@@ -551,6 +642,8 @@ 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,

-- 
2.51.2

On Mon Dec 22, 2025 at 11:11 AM CET, Louis Chauvet wrote:
> 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>

> --- 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

This should be Jan 2026 I guess. Same for the previous patches in the
series which I already reviewed, sorry I didn't notice before.

BTW I wonder whether it is really important to have a date here. The time
before a patch is applied can make it quite wrong, but mostly I don't see
an obvious usefulness.

> --- a/drivers/gpu/drm/vkms/vkms_configfs.c
> +++ b/drivers/gpu/drm/vkms/vkms_configfs.c

> +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);;

Double semicolon.

> +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;
> +	/* Should at least provide one color range */
> +	if ((val & VKMS_SUPPORTED_COLOR_RANGES) == 0)
> +		return -EINVAL;

As for patch 13, these 3 lines are redundant, the is_power_of_2() below is
enough.

> +
> +	if (!is_power_of_2(val))
> +		return -EINVAL;
> +
> +	/* Convert bit position to the proper enum value */
> +	val = __ffs(val) + DRM_COLOR_YCBCR_LIMITED_RANGE;
                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

I wonder whether this should just be '+ 1'. After all it's just the __ffs
semantics counting from 1 as opposed to the BIT() semantics counting from
0. Any pair of BIT() to read and __ffs() to write will need a '+ 1',
regardless of the meaning of the bits.

Same in patch 13, but realized just now.

Luca

--
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com