[PATCH v4 14/37] drm/vkms: Introduce configfs for plane name

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

Planes can have name, create a plane attribute to configure it. Currently
plane name is mainly used in logs.

Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>
---
 Documentation/ABI/testing/configfs-vkms |  6 ++++
 Documentation/gpu/vkms.rst              |  3 +-
 drivers/gpu/drm/vkms/vkms_configfs.c    | 62 +++++++++++++++++++++++++++++++++
 3 files changed, 70 insertions(+), 1 deletion(-)

diff --git a/Documentation/ABI/testing/configfs-vkms b/Documentation/ABI/testing/configfs-vkms
index a1a3e186e50a..642d0dad8cca 100644
--- a/Documentation/ABI/testing/configfs-vkms
+++ b/Documentation/ABI/testing/configfs-vkms
@@ -103,6 +103,12 @@ Description:
 	Plane type. Possible values: 0 - overlay, 1 - primary,
 	2 - cursor.
 
+What:		/sys/kernel/config/vkms/<device>/planes/<plane>/name
+Date:		Nov 2025
+Contact:	dri-devel@lists.freedesktop.org
+Description:
+	Name of the plane.
+
 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 1e79e62a6bc4..79f1185d8645 100644
--- a/Documentation/gpu/vkms.rst
+++ b/Documentation/gpu/vkms.rst
@@ -87,10 +87,11 @@ Start by creating one or more planes::
 
   sudo mkdir /config/vkms/my-vkms/planes/plane0
 
-Planes have 1 configurable attribute:
+Planes have 2 configurable attributes:
 
 - type: Plane type: 0 overlay, 1 primary, 2 cursor (same values as those
   exposed by the "type" property of a plane)
+- name: Name of the plane. Allowed characters are [A-Za-z1-9_-]
 
 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 97f87a53d202..e8d5792b0873 100644
--- a/drivers/gpu/drm/vkms/vkms_configfs.c
+++ b/drivers/gpu/drm/vkms/vkms_configfs.c
@@ -324,10 +324,72 @@ static ssize_t plane_type_store(struct config_item *item, const char *page,
 	return (ssize_t)count;
 }
 
+static ssize_t plane_name_show(struct config_item *item, char *page)
+{
+	struct vkms_configfs_plane *plane;
+	const char *name;
+
+	plane = plane_item_to_vkms_configfs_plane(item);
+
+	scoped_guard(mutex, &plane->dev->lock)
+		name = vkms_config_plane_get_name(plane->config);
+
+	if (name)
+		return sysfs_emit(page, "%s\n", name);
+
+	return sysfs_emit(page, "\n");
+}
+
+static ssize_t plane_name_store(struct config_item *item, const char *page,
+				size_t count)
+{
+	struct vkms_configfs_plane *plane;
+	char name_tmp[PAGE_SIZE];
+	size_t str_len;
+	int ret;
+
+	memcpy(name_tmp, page, PAGE_SIZE);
+
+	plane = plane_item_to_vkms_configfs_plane(item);
+
+	// strspn is not lenght-protected, ensure that page is a null-terminated string.
+	str_len = strnlen(name_tmp, count);
+	if (str_len > count)
+		return -EINVAL;
+
+	if (count > 0) {
+		size_t expected_count = count;
+
+		if (name_tmp[count-1] == '\n') {
+			expected_count = count - 1;
+			name_tmp[count-1] = '\0';
+		}
+
+		if (strspn(name_tmp,
+			   "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_-")
+		    != expected_count)
+			return -EINVAL;
+	}
+
+
+	scoped_guard(mutex, &plane->dev->lock) {
+		if (plane->dev->enabled)
+			return -EBUSY;
+
+		ret = vkms_config_plane_set_name(plane->config, name_tmp);
+		if (ret)
+			return ret;
+	}
+
+	return (ssize_t)count;
+}
+
 CONFIGFS_ATTR(plane_, type);
+CONFIGFS_ATTR(plane_, name);
 
 static struct configfs_attribute *plane_item_attrs[] = {
 	&plane_attr_type,
+	&plane_attr_name,
 	NULL,
 };
 

-- 
2.54.0