[PATCH v3 28/33] drm/vkms: Introduce configfs for connector EDID

Louis Chauvet
2025-12-22T10:12:41Z

Introduce new attributes to configure EDID of a connector:
- edid_enable - chose if the connector will have an EDID or not
- edid - raw edid content

Due to limitation of ConfigFS, the max len of EDID is PAGE_SIZE (4kB on
x86), it should be sufficient for many tests. One possible evolution is
using a ConfigFS blob to allow bigger EDID.

Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>
---
Documentation/ABI/testing/configfs-vkms | 14 ++++++
Documentation/gpu/vkms.rst | 5 ++-
drivers/gpu/drm/vkms/vkms_configfs.c | 80 +++++++++++++++++++++++++++++++++
drivers/gpu/drm/vkms/vkms_connector.c | 3 ++
4 files changed, 101 insertions(+), 1 deletion(-)

diff --git a/Documentation/ABI/testing/configfs-vkms b/Documentation/ABI/testing/configfs-vkms
index f750e616be54..4061ada5d88b 100644
--- a/Documentation/ABI/testing/configfs-vkms
+++ b/Documentation/ABI/testing/configfs-vkms
@@ -48,6 +48,20 @@ Description:
Value is a bitfield, where 0x1 = NO_DATA, 0x2 = SMPTE_170M_YCC,
etc. See enum drm_colorspace for full list.

+What: /sys/kernel/config/vkms/<device>/connectors/<connector>/edid_enabled
+Date: Nov 2025
+Contact: dri-devel@lists.freedesktop.org
+Description:
+ Enable or disable EDID for this connector. Value:
+ 1 - enabled, 0 - disabled.
+
+What: /sys/kernel/config/vkms/<device>/connectors/<connector>/edid
+Date: Nov 2025
+Contact: dri-devel@lists.freedesktop.org
+Description:
+ Content of the EDID for this connector. Ignored if
+ edid_enabled is not set.
+
What: /sys/kernel/config/vkms/<device>/connectors/<connector>/possible_encoders
Date: Nov 2025
Contact: dri-devel@lists.freedesktop.org
diff --git a/Documentation/gpu/vkms.rst b/Documentation/gpu/vkms.rst
index 1c4a8023374c..60367fd1bd65 100644
--- a/Documentation/gpu/vkms.rst
+++ b/Documentation/gpu/vkms.rst
@@ -138,7 +138,7 @@ Last but not least, create one or more connectors::

sudo mkdir /config/vkms/my-vkms/connectors/connector0

-Connectors have 3 configurable attribute:
+Connectors have 5 configurable attribute:

- status: Connection status: 1 connected, 2 disconnected, 3 unknown (same values
as those exposed by the "status" property of a connector)
@@ -147,6 +147,9 @@ Connectors have 3 configurable attribute:
If supported_colorspaces is not 0, the HDR_OUTPUT_METADATA will also be created.
Value is a bitfield, 0x1 = NO_DATA, 0x2 = SMPTE_170M_YCC... see enum drm_colorspace
for full list.
+- edid_enabled: Enable or not EDID for this connector. Some connectors may not have an
+ EDID but just a list of modes, this attribute allows to disable EDID property.
+- edid: Content of the EDID. Ignored if edid_enabled is not set

To finish the configuration, link the different pipeline items::
diff --git a/drivers/gpu/drm/vkms/vkms_configfs.c b/drivers/gpu/drm/vkms/vkms_configfs.c
index 90bf6e6995ae..20f5150e8b24 100644
--- a/drivers/gpu/drm/vkms/vkms_configfs.c
+++ b/drivers/gpu/drm/vkms/vkms_configfs.c
@@ -1271,14 +1271,94 @@ static ssize_t connector_supported_colorspaces_store(struct config_item *item,
return count;
}

+static ssize_t connector_edid_enabled_show(struct config_item *item, char *page)
+{
+ struct vkms_configfs_connector *connector;
+ bool enabled;
+
+ connector = connector_item_to_vkms_configfs_connector(item);
+
+ scoped_guard(mutex, &connector->dev->lock)
+ enabled = vkms_config_connector_get_edid_enabled(connector->config);
+
+ return sprintf(page, "%d\n", enabled);
+}
+
+static ssize_t connector_edid_enabled_store(struct config_item *item,
+ const char *page, size_t count)
+{
+ struct vkms_configfs_connector *connector;
+ struct vkms_config_connector *connector_cfg;
+ bool enabled;
+
+ connector = connector_item_to_vkms_configfs_connector(item);
+ connector_cfg = connector->config;
+
+ if (kstrtobool(page, &enabled))
+ return -EINVAL;
+
+ scoped_guard(mutex, &connector->dev->lock)
+ {
+ vkms_config_connector_set_edid_enabled(connector_cfg, enabled);
+
+ if (connector->dev->enabled &&
+ vkms_config_connector_get_status(connector_cfg) !=
+ connector_status_disconnected)
+ vkms_trigger_connector_hotplug(connector->dev->config->dev);
+ }
+ return count;
+}
+
+static ssize_t connector_edid_show(struct config_item *item, char *page)
+{
+ struct vkms_configfs_connector *connector;
+
+ connector = connector_item_to_vkms_configfs_connector(item);
+
+ scoped_guard(mutex, &connector->dev->lock)
+ {
+ unsigned int len = 0;
+ const u8 *edid = vkms_config_connector_get_edid(connector->config, &len);
+
+ memcpy(page, edid, min(len, PAGE_SIZE));
+ return min(len, PAGE_SIZE);
+ }
+
+ return -EINVAL;
+}
+
+static ssize_t connector_edid_store(struct config_item *item,
+ const char *page, size_t count)
+{
+ struct vkms_configfs_connector *connector;
+
+ connector = connector_item_to_vkms_configfs_connector(item);
+
+ scoped_guard(mutex, &connector->dev->lock)
+ {
+ vkms_config_connector_set_edid(connector->config, page, count);
+
+ if (connector->dev->enabled &&
+ vkms_config_connector_get_status(connector->config) !=
+ connector_status_disconnected)
+ vkms_trigger_connector_hotplug(connector->dev->config->dev);
+ }
+
+ return count;
+}
+
CONFIGFS_ATTR(connector_, status);
CONFIGFS_ATTR(connector_, type);
CONFIGFS_ATTR(connector_, supported_colorspaces);
+CONFIGFS_ATTR(connector_, edid_enabled);
+CONFIGFS_ATTR(connector_, edid);

static struct configfs_attribute *connector_item_attrs[] = {
&connector_attr_status,
&connector_attr_type,
&connector_attr_supported_colorspaces,
+ &connector_attr_edid_enabled,
+ &connector_attr_edid,
NULL,
};

diff --git a/drivers/gpu/drm/vkms/vkms_connector.c b/drivers/gpu/drm/vkms/vkms_connector.c
index c85d19013720..311858727175 100644
--- a/drivers/gpu/drm/vkms/vkms_connector.c
+++ b/drivers/gpu/drm/vkms/vkms_connector.c
@@ -143,6 +143,9 @@ struct vkms_connector *vkms_connector_init(struct vkms_device *vkmsdev,

drm_connector_helper_add(&connector->base, &vkms_conn_helper_funcs);

+ if (vkms_config_connector_get_edid_enabled(connector_cfg))
+ drm_connector_attach_edid_property(&connector->base);
+
return connector;
}

--
2.51.2