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

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

[Aaron Thompson]

From: Aaron Thompson <dev@aaront.org>

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: stable@vger.kernel.org
Signed-off-by: Aaron Thompson <dev@aaront.org>
---
 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(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_debugfs.c b/drivers/gpu/drm/nouveau/nouveau_debugfs.c
index 200e65a7cefc..c7869a639bef 100644
--- a/drivers/gpu/drm/nouveau/nouveau_debugfs.c
+++ b/drivers/gpu/drm/nouveau/nouveau_debugfs.c
@@ -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
diff --git a/drivers/gpu/drm/nouveau/nouveau_debugfs.h b/drivers/gpu/drm/nouveau/nouveau_debugfs.h
index b7617b344ee2..d05ed0e641c4 100644
--- a/drivers/gpu/drm/nouveau/nouveau_debugfs.h
+++ b/drivers/gpu/drm/nouveau/nouveau_debugfs.h
@@ -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
diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c b/drivers/gpu/drm/nouveau/nouveau_drm.c
index 0c82a63cd49d..1527b801f013 100644
--- a/drivers/gpu/drm/nouveau/nouveau_drm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_drm.c
@@ -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
-- 
2.39.5

Re: [PATCH] drm/nouveau: Do not fail module init on debugfs errors

[Timur Tabi]

On Thu, 2025-07-03 at 21:19 +0000, Aaron Thompson wrote:
> From: Aaron Thompson <dev@aaront.org>
> 
> 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")

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

Acked-by: Timur Tabi <ttabi@nvidia.com>

Re: [PATCH] drm/nouveau: Do not fail module init on debugfs errors

[Danilo Krummrich]

On Thu, Jul 03, 2025 at 09:19:49PM +0000, Aaron Thompson wrote:
> From: Aaron Thompson <dev@aaront.org>
> 
> 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: stable@vger.kernel.org
> Signed-off-by: Aaron Thompson <dev@aaront.org>

Applied to drm-misc-fixes, thanks!