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

The supported color encoding are configured by writing a color encoding
bitmask to the file `supported_color_encoding` and the default color
encoding is chosen by writing a color encoding bitmask to
`default_color_encoding`.

Signed-off-by: Louis Chauvet <[email protected]>
---
 Documentation/ABI/testing/configfs-vkms | 14 +++++
 Documentation/gpu/vkms.rst              |  8 ++-
 drivers/gpu/drm/vkms/vkms_configfs.c    | 97 +++++++++++++++++++++++++++++++++
 3 files changed, 118 insertions(+), 1 deletion(-)

diff --git a/Documentation/ABI/testing/configfs-vkms 
b/Documentation/ABI/testing/configfs-vkms
index 9b74375bbf35..242aae91289c 100644
--- a/Documentation/ABI/testing/configfs-vkms
+++ b/Documentation/ABI/testing/configfs-vkms
@@ -124,6 +124,20 @@ Description:
         Default rotation presented to userspace, same values as
         possible_rotations.
 
+What:          
/sys/kernel/config/vkms/<device>/planes/<plane>/supported_color_encoding
+Date:          Nov 2025
+Contact:       [email protected]
+Description:
+        Available color encodings for the plane, as a bitmask:
+        0x01 - YCBCR_BT601, 0x02 - YCBCR_BT709, 0x04 - YCBCR_BT2020.
+
+What:          
/sys/kernel/config/vkms/<device>/planes/<plane>/default_color_encoding
+Date:          Nov 2025
+Contact:       [email protected]
+Description:
+        Default color encoding presented to userspace, same
+        values as supported_color_encoding.
+
 What:          /sys/kernel/config/vkms/<device>/planes/<plane>/possible_crtcs
 Date:          Nov 2025
 Contact:       [email protected]
diff --git a/Documentation/gpu/vkms.rst b/Documentation/gpu/vkms.rst
index 7fd746dd6ee2..0d4dae3ba8e5 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 4 configurable attributes:
+Planes have 6 configurable attributes:
 
 - type: Plane type: 0 overlay, 1 primary, 2 cursor (same values as those
   exposed by the "type" property of a plane)
@@ -97,6 +97,12 @@ Planes have 4 configurable attributes:
   (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.
+- 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
+  must be set too.
+- default_color_encoding: Default color encoding presented to the userspace, 
same
+  values as supported_color_encodings
 
 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 bcc3e222e6b3..755978b17c95 100644
--- a/drivers/gpu/drm/vkms/vkms_configfs.c
+++ b/drivers/gpu/drm/vkms/vkms_configfs.c
@@ -9,6 +9,14 @@
 #include "vkms_configfs.h"
 #include "vkms_connector.h"
 
+/**
+ * VKMS_SUPPORTED_COLOR_ENCODINGS - Bitmask of all supported color encodings 
in VKMS
+ */
+#define VKMS_SUPPORTED_COLOR_ENCODINGS (       \
+       BIT(DRM_COLOR_YCBCR_BT601) |            \
+       BIT(DRM_COLOR_YCBCR_BT709) |            \
+       BIT(DRM_COLOR_YCBCR_BT2020))
+
 /* To avoid registering configfs more than once or unregistering on error */
 static bool is_configfs_registered;
 
@@ -446,16 +454,105 @@ static ssize_t plane_default_rotation_store(struct 
config_item *item,
        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);
+       unsigned int supported_color_encodings;
+
+       scoped_guard(mutex, &plane->dev->lock)
+               supported_color_encodings = 
vkms_config_plane_get_supported_color_encodings(plane->config);
+
+       return sprintf(page, "%u", supported_color_encodings);
+}
+
+static ssize_t plane_supported_color_encodings_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_ENCODINGS))
+               return -EINVAL;
+       /* Should at least provide one color range */
+       if ((val & (VKMS_SUPPORTED_COLOR_ENCODINGS)) == 0)
+               return -EINVAL;
+
+       scoped_guard(mutex, &plane->dev->lock) {
+               if (plane->dev->enabled)
+                       return -EBUSY;
+
+               vkms_config_plane_set_supported_color_encodings(plane->config, 
val);
+       }
+
+       return count;
+}
+
+static ssize_t plane_default_color_encoding_show(struct config_item *item, 
char *page)
+{
+       struct vkms_configfs_plane *plane;
+       unsigned int default_color_encoding;
+
+       plane = plane_item_to_vkms_configfs_plane(item);
+
+       scoped_guard(mutex, &plane->dev->lock)
+               default_color_encoding = 
BIT(vkms_config_plane_get_default_color_encoding(plane->config));
+
+       return sprintf(page, "%u", default_color_encoding);
+}
+
+static ssize_t plane_default_color_encoding_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_ENCODINGS)
+               return -EINVAL;
+       /* Should at least provide one color range */
+       if ((val & VKMS_SUPPORTED_COLOR_ENCODINGS) == 0)
+               return -EINVAL;
+
+       /* Ensure val is a single bit set */
+       if (!is_power_of_2(val))
+               return -EINVAL;
+
+       /* Convert bit position to the proper enum value */
+       val = __ffs(val) + DRM_COLOR_YCBCR_BT601;
+
+       scoped_guard(mutex, &plane->dev->lock) {
+               if (plane->dev->enabled)
+                       return -EBUSY;
+
+               vkms_config_plane_set_default_color_encoding(plane->config, 
val);
+       }
+
+       return count;
+}
+
 CONFIGFS_ATTR(plane_, type);
 CONFIGFS_ATTR(plane_, name);
 CONFIGFS_ATTR(plane_, supported_rotations);
 CONFIGFS_ATTR(plane_, default_rotation);
+CONFIGFS_ATTR(plane_, supported_color_encodings);
+CONFIGFS_ATTR(plane_, default_color_encoding);
 
 static struct configfs_attribute *plane_item_attrs[] = {
        &plane_attr_type,
        &plane_attr_name,
        &plane_attr_supported_rotations,
        &plane_attr_default_rotation,
+       &plane_attr_supported_color_encodings,
+       &plane_attr_default_color_encoding,
        NULL,
 };
 

-- 
2.51.2

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