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drm/nouveau: Do not fail module init on debugfs errors

PATCH Applied Aaron Thompson 3 participants 3 messages Jul 3, 2025

Subsystems (4)
Stable branch DRM drivers DRM misc nouveau
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Aaron Thompson

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#0 lore raw

PATCH 1/1 drm/nouveau: Do not fail module init on debugfs errors

From: Aaron Thompson <[email protected]>

If CONFIG_DEBUG_FS is enabled, nouveau_drm_init() returns an error if it fails to create the "nouveau" directory in debugfs. One case where that will happen is when debugfs access is restricted by CONFIG_DEBUG_FS_ALLOW_NONE or by the boot parameter debugfs=off, which cause the debugfs APIs to return -EPERM.

So just ignore errors from debugfs. Note that nouveau_debugfs_root may be an error now, but that is a standard pattern for debugfs. From include/linux/debugfs.h:

"NOTE: it's expected that most callers should _ignore_ the errors returned by this function. Other debugfs functions handle the fact that the "dentry" passed to them could be an error and they don't crash in that case. Drivers should generally work fine even if debugfs fails to init anyway."

Fixes 97118a1816d2 ("drm/nouveau: create module debugfs root")
Cc [email protected]
Signed-off-by Aaron Thompson <[email protected]>
---
 drivers/gpu/drm/nouveau/nouveau_debugfs.c | 6 +-----
 drivers/gpu/drm/nouveau/nouveau_debugfs.h | 5 ++---
 drivers/gpu/drm/nouveau/nouveau_drm.c     | 4 +---
 3 files changed, 4 insertions(+), 11 deletions(-)
drivers/gpu/drm/nouveau/nouveau_debugfs.c +1 -5
index 200e65a7cefc..c7869a639bef 100644
@@ -314,14 +314,10 @@ nouveau_debugfs_fini(struct nouveau_drm *drm)
 	drm->debugfs = NULL;
 }
 
-int
+void
 nouveau_module_debugfs_init(void)
 {
 	nouveau_debugfs_root = debugfs_create_dir("nouveau", NULL);
-	if (IS_ERR(nouveau_debugfs_root))
-		return PTR_ERR(nouveau_debugfs_root);
-
-	return 0;
 }
 
 void
drivers/gpu/drm/nouveau/nouveau_debugfs.h +2 -3
index b7617b344ee2..d05ed0e641c4 100644
@@ -24,7 +24,7 @@ extern void nouveau_debugfs_fini(struct nouveau_drm *);
 
 extern struct dentry *nouveau_debugfs_root;
 
-int  nouveau_module_debugfs_init(void);
+void nouveau_module_debugfs_init(void);
 void nouveau_module_debugfs_fini(void);
 #else
 static inline void

@@ -42,10 +42,9 @@ nouveau_debugfs_fini(struct nouveau_drm *drm)
 {
 }
 
-static inline int
+static inline void
 nouveau_module_debugfs_init(void)
 {
-	return 0;
 }
 
 static inline void
drivers/gpu/drm/nouveau/nouveau_drm.c +1 -3
index 0c82a63cd49d..1527b801f013 100644
@@ -1461,9 +1461,7 @@ nouveau_drm_init(void)
 	if (!nouveau_modeset)
 		return 0;
 
-	ret = nouveau_module_debugfs_init();
-	if (ret)
-		return ret;
+	nouveau_module_debugfs_init();
 
 #ifdef CONFIG_NOUVEAU_PLATFORM_DRIVER
 	platform_driver_register(&nouveau_platform_driver);

base-commit: d0b3b7b22dfa1f4b515fd3a295b3fd958f9e81af

Signature · 1 line
2.39.5
Acked-by on v1 1/1
#1 lore raw
Quoted 12 lines · Aaron Thompson

From: Aaron Thompson <[email protected]>

If CONFIG_DEBUG_FS is enabled, nouveau_drm_init() returns an error if it fails to create the "nouveau" directory in debugfs. One case where that will happen is when debugfs access is restricted by CONFIG_DEBUG_FS_ALLOW_NONE or by the boot parameter debugfs=off, which cause the debugfs APIs to return -EPERM.

So just ignore errors from debugfs. Note that nouveau_debugfs_root may be an error now, but that is a standard pattern for debugfs. From include/linux/debugfs.h:

Quoted 7 lines

"NOTE: it's expected that most callers should _ignore_ the errors returned by this function. Other debugfs functions handle the fact that the "dentry" passed to them could be an error and they don't crash in that case. Drivers should generally work fine even if debugfs fails to init anyway."

Fixes 97118a1816d2 ("drm/nouveau: create module debugfs root")

Oof, sorry about that. I should have noticed this behavior when I reviewed this patch.

Acked-by Timur Tabi <[email protected]>
maintainer Applied
#2 lore raw
In reply to Aaron Thompson
Quoted 18 lines · Aaron Thompson

From: Aaron Thompson <[email protected]>

If CONFIG_DEBUG_FS is enabled, nouveau_drm_init() returns an error if it fails to create the "nouveau" directory in debugfs. One case where that will happen is when debugfs access is restricted by CONFIG_DEBUG_FS_ALLOW_NONE or by the boot parameter debugfs=off, which cause the debugfs APIs to return -EPERM.

So just ignore errors from debugfs. Note that nouveau_debugfs_root may be an error now, but that is a standard pattern for debugfs. From include/linux/debugfs.h:

"NOTE: it's expected that most callers should _ignore_ the errors returned by this function. Other debugfs functions handle the fact that the "dentry" passed to them could be an error and they don't crash in that case. Drivers should generally work fine even if debugfs fails to init anyway."

Quoted 3 lines
Fixes 97118a1816d2 ("drm/nouveau: create module debugfs root")
Cc [email protected]
Signed-off-by Aaron Thompson <[email protected]>

Applied to drm-misc-fixes, thanks!