Re: [PATCH RESEND v2 05/32] drm/vkms: Introduce config for plane name

[Louis Chauvet]

On 11/13/25 14:17, José Expósito wrote:

On Wed, Oct 29, 2025 at 03:36:42PM +0100, Louis Chauvet wrote:

As planes can have a name in DRM, prepare VKMS to configure it using
ConfigFS.

Signed-off-by: Louis Chauvet <louis.chau...@bootlin.com>
---
  drivers/gpu/drm/vkms/vkms_config.c |  4 ++++
  drivers/gpu/drm/vkms/vkms_config.h | 26 ++++++++++++++++++++++++++
  drivers/gpu/drm/vkms/vkms_drv.h    |  5 +++--
  drivers/gpu/drm/vkms/vkms_output.c |  6 +-----
  drivers/gpu/drm/vkms/vkms_plane.c  |  6 ++++--
  5 files changed, 38 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/vkms/vkms_config.c 
b/drivers/gpu/drm/vkms/vkms_config.c
index 858bec2d1312..bfafb5d2504d 100644
--- a/drivers/gpu/drm/vkms/vkms_config.c
+++ b/drivers/gpu/drm/vkms/vkms_config.c
@@ -352,6 +352,8 @@ static int vkms_config_show(struct seq_file *m, void *data)
                seq_puts(m, "plane:\n");
                seq_printf(m, "\ttype=%s\n",
                           
drm_get_plane_type_name(vkms_config_plane_get_type(plane_cfg)));
+               seq_printf(m, "\tname=%s\n",
+                          vkms_config_plane_get_name(plane_cfg));

I discovered this while working on some basic IGT tests to validate
your changes.

I think that this triggers undefined behavior. printf() and friends
expect a non NULL value for %s:
https://stackoverflow.com/a/11589479

In my Fedora system, this prints "name=(null)", instead of an empty
string.

The same happens with the ConfigFS API:

$ cat /sys/kernel/config/vkms/test_plane_default_values/planes/plane0/name
(null)

We'd need to return in both places an empty string instead.

Good catch, I will fix for v3!

        }

vkms_config_for_each_crtc(vkmsdev->config, crtc_cfg) {

@@ -392,6 +394,7 @@ struct vkms_config_plane *vkms_config_create_plane(struct 
vkms_config *config)

plane_cfg->config = config;

        vkms_config_plane_set_type(plane_cfg, DRM_PLANE_TYPE_OVERLAY);
+       vkms_config_plane_set_name(plane_cfg, NULL);
        xa_init_flags(&plane_cfg->possible_crtcs, XA_FLAGS_ALLOC);

list_add_tail(&plane_cfg->link, &config->planes);

@@ -404,6 +407,7 @@ void vkms_config_destroy_plane(struct vkms_config_plane 
*plane_cfg)
  {
        xa_destroy(&plane_cfg->possible_crtcs);
        list_del(&plane_cfg->link);
+       kfree_const(plane_cfg->name);
        kfree(plane_cfg);
  }
  EXPORT_SYMBOL_IF_KUNIT(vkms_config_destroy_plane);
diff --git a/drivers/gpu/drm/vkms/vkms_config.h 
b/drivers/gpu/drm/vkms/vkms_config.h
index 4c8d668e7ef8..57342db5795a 100644
--- a/drivers/gpu/drm/vkms/vkms_config.h
+++ b/drivers/gpu/drm/vkms/vkms_config.h
@@ -35,6 +35,7 @@ struct vkms_config {
   *
   * @link: Link to the others planes in vkms_config
   * @config: The vkms_config this plane belongs to
+ * @name: Name of the plane
   * @type: Type of the plane. The creator of configuration needs to ensures 
that
   *        at least one primary plane is present.
   * @possible_crtcs: Array of CRTCs that can be used with this plane
@@ -47,6 +48,7 @@ struct vkms_config_plane {
        struct list_head link;
        struct vkms_config *config;

+ const char *name;

        enum drm_plane_type type;
        struct xarray possible_crtcs;

@@ -288,6 +290,30 @@ vkms_config_plane_set_type(struct vkms_config_plane *plane_cfg,

        plane_cfg->type = type;
  }

+/**

+ * vkms_config_plane_set_name() - Set the plane name
+ * @plane_cfg: Plane to set the name to
+ * @name: New plane name. The name is copied.
+ */
+static inline void
+vkms_config_plane_set_name(struct vkms_config_plane *plane_cfg,
+                          const char *name)
+{
+       if (plane_cfg->name)
+               kfree_const(plane_cfg->name);
+       plane_cfg->name = kstrdup_const(name, GFP_KERNEL);
+}
+
+/**
+ * vkms_config_plane_get_name - Get the plane name
+ * @plane_cfg: Plane to get the name from
+ */
+static inline const char *
+vkms_config_plane_get_name(const struct vkms_config_plane *plane_cfg)
+{
+       return plane_cfg->name;
+}
+
  /**
   * vkms_config_plane_attach_crtc - Attach a plane to a CRTC
   * @plane_cfg: Plane to attach
diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
index db260df1d4f6..9ad286f043b5 100644
--- a/drivers/gpu/drm/vkms/vkms_drv.h
+++ b/drivers/gpu/drm/vkms/vkms_drv.h
@@ -225,6 +225,7 @@ struct vkms_output {
  };

struct vkms_config;

+struct vkms_config_plane;

/**

   * struct vkms_device - Description of a VKMS device
@@ -298,10 +299,10 @@ int vkms_output_init(struct vkms_device *vkmsdev);
   * vkms_plane_init() - Initialize a plane
   *
   * @vkmsdev: VKMS device containing the plane
- * @type: type of plane to initialize
+ * @config: plane configuration
   */
  struct vkms_plane *vkms_plane_init(struct vkms_device *vkmsdev,
-                                  enum drm_plane_type type);
+                                  struct vkms_config_plane *config);

/* CRC Support */

  const char *const *vkms_get_crc_sources(struct drm_crtc *crtc,
diff --git a/drivers/gpu/drm/vkms/vkms_output.c 
b/drivers/gpu/drm/vkms/vkms_output.c
index 2ee3749e2b28..22208d02afa4 100644
--- a/drivers/gpu/drm/vkms/vkms_output.c
+++ b/drivers/gpu/drm/vkms/vkms_output.c
@@ -19,11 +19,7 @@ int vkms_output_init(struct vkms_device *vkmsdev)
                return -EINVAL;

vkms_config_for_each_plane(vkmsdev->config, plane_cfg) {

-               enum drm_plane_type type;
-
-               type = vkms_config_plane_get_type(plane_cfg);
-
-               plane_cfg->plane = vkms_plane_init(vkmsdev, type);
+               plane_cfg->plane = vkms_plane_init(vkmsdev, plane_cfg);
                if (IS_ERR(plane_cfg->plane)) {
                        DRM_DEV_ERROR(dev->dev, "Failed to init vkms plane\n");
                        return PTR_ERR(plane_cfg->plane);
diff --git a/drivers/gpu/drm/vkms/vkms_plane.c 
b/drivers/gpu/drm/vkms/vkms_plane.c
index e592e47a5736..73180cbb78b1 100644
--- a/drivers/gpu/drm/vkms/vkms_plane.c
+++ b/drivers/gpu/drm/vkms/vkms_plane.c
@@ -9,6 +9,7 @@
  #include <drm/drm_gem_atomic_helper.h>
  #include <drm/drm_gem_framebuffer_helper.h>

+#include "vkms_config.h"

  #include "vkms_drv.h"
  #include "vkms_formats.h"

@@ -217,7 +218,7 @@ static const struct drm_plane_helper_funcs vkms_plane_helper_funcs = {

  };

struct vkms_plane *vkms_plane_init(struct vkms_device *vkmsdev,

-                                  enum drm_plane_type type)
+                                  struct vkms_config_plane *config)
  {
        struct drm_device *dev = &vkmsdev->drm;
        struct vkms_plane *plane;
@@ -225,7 +226,8 @@ struct vkms_plane *vkms_plane_init(struct vkms_device 
*vkmsdev,
        plane = drmm_universal_plane_alloc(dev, struct vkms_plane, base, 0,
                                           &vkms_plane_funcs,
                                           vkms_formats, 
ARRAY_SIZE(vkms_formats),
-                                          NULL, type, NULL);
+                                          NULL, 
vkms_config_plane_get_type(config),
+                                          vkms_config_plane_get_name(config));
        if (IS_ERR(plane))
                return plane;

--
2.51.0