On 12/23/25 12:14, Luca Ceresoli wrote:
On Mon Dec 22, 2025 at 11:11 AM CET, Louis Chauvet wrote:
Planes can have name, create a plane attribute to configure it. Currently
plane name is mainly used in logs.
Signed-off-by: Louis Chauvet <[email protected]>
---
Documentation/ABI/testing/configfs-vkms | 6 +++++
Documentation/gpu/vkms.rst | 3 ++-
drivers/gpu/drm/vkms/vkms_configfs.c | 43 +++++++++++++++++++++++++++++++++
3 files changed, 51 insertions(+), 1 deletion(-)
diff --git a/Documentation/ABI/testing/configfs-vkms
b/Documentation/ABI/testing/configfs-vkms
index 0beaa25f30ba..6fe375d1636f 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: [email protected]
+Description:
+ Name of the plane.
+
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 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 506666e21c91..989788042191 100644
--- a/drivers/gpu/drm/vkms/vkms_configfs.c
+++ b/drivers/gpu/drm/vkms/vkms_configfs.c
@@ -324,10 +324,53 @@ 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);
vkms_config_plane_get_name() returns a pointer to the name string, not a
copy. Unless I'm missing something, that string might be freed before the
next lines, where it is used:
+
+ if (name)
+ return sprintf(page, "%s\n", name);
+ return sprintf(page, "\n");
So for safety the above 3 lines whould go inside the scoped_guard().
Good catch!
This also raised some questions on the whole locking synchronization
between configfs / config / DRM core. I will work on this topic and
maybe move the mutex / add a refcount to vkms_config.
+}
+
+static ssize_t plane_name_store(struct config_item *item, const char *page,
+ size_t count)
+{
+ struct vkms_configfs_plane *plane;
+ size_t str_len;
+
+ plane = plane_item_to_vkms_configfs_plane(item);
+
+ // strspn is not lenght-protected, ensure that page is a
null-terminated string.
+ str_len = strnlen(page, count);
+ if (str_len >= count)
+ return -EINVAL;
+
+ if (strspn(page,
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_-") != count -
1)
+ return -EINVAL;
I see you effor to make this as clean as possible, thanks. Still this is a
tad ugly, and should be moved to some common place at some point IMO. For
now it's fine, but if you need to add more user-passed strings, that could
be the moment to move this code.
There are multiple "user strings" in this file (notably group names),
but currently without limitation.
I can create a tiny helper and limit all user strings to a-zA-Z0-9_-
It will technically break the ABI, but I don't think this is a big issue.
Do you or José think this is a good idea? If so I can extract the helper
for v4 and send a separate series to do the limitation on other strings.
Luca
--
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
