[PATCH v4 18/37] drm/vkms: Introduce configfs for plane color encoding

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

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 <louis.chauvet@bootlin.com>
---
 Documentation/ABI/testing/configfs-vkms | 14 +++++
 Documentation/gpu/vkms.rst              |  8 ++-
 drivers/gpu/drm/vkms/vkms_configfs.c    | 92 +++++++++++++++++++++++++++++++++
 3 files changed, 113 insertions(+), 1 deletion(-)

diff --git a/Documentation/ABI/testing/configfs-vkms b/Documentation/ABI/testing/configfs-vkms
index 55472f4e721d..836169910884 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_encodings
+Date:		Nov 2025
+Contact:	dri-devel@lists.freedesktop.org
+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:	dri-devel@lists.freedesktop.org
+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:	dri-devel@lists.freedesktop.org
diff --git a/Documentation/gpu/vkms.rst b/Documentation/gpu/vkms.rst
index 034565eb43ad..4b3dfbe4e13a 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
   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
+  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 5ed6a7fa6046..a5174fc8321c 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;
 
@@ -462,16 +470,100 @@ 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 encoding */
+	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 = plane = plane_item_to_vkms_configfs_plane(item);
+	unsigned int default_color_encoding;
+
+	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;
+
+	/* 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,
 };
 

-- 
2.54.0