| Message ID | 20211011190607.104618-4-nirmoy.das@amd.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/4] dri: do not check for NULL debugfs dentry | expand |
On Mon, Oct 11, 2021 at 09:06:07PM +0200, Nirmoy Das wrote: > Debugfs APIs returns encoded error on failure so use > debugfs_lookup() instead of checking for NULL. [...] > --- a/drivers/gpu/vga/vga_switcheroo.c > +++ b/drivers/gpu/vga/vga_switcheroo.c > @@ -914,7 +914,7 @@ static void vga_switcheroo_debugfs_fini(struct vgasr_priv *priv) > static void vga_switcheroo_debugfs_init(struct vgasr_priv *priv) > { > /* already initialised */ > - if (priv->debugfs_root) > + if (debugfs_lookup("vgaswitcheroo", NULL)) > return; > > priv->debugfs_root = debugfs_create_dir("vgaswitcheroo", NULL); If debugfs_create_dir() returns an error code, it does make sense to retry the call when another vga_switcheroo client registers later. I like that. However I'd prefer simply changing this to explicitly check for NULL, i.e.: - if (priv->debugfs_root) + if (priv->debugfs_root == NULL) It's just as clear as calling debugfs_lookup() and it has way less overhead. Granted, this isn't a hot path, but it's called on boot, and the less code we execute, the faster the machine boots. Thanks, Lukas
On Mon, Oct 11, 2021 at 10:24:29PM +0200, Lukas Wunner wrote: > On Mon, Oct 11, 2021 at 09:06:07PM +0200, Nirmoy Das wrote: > > Debugfs APIs returns encoded error on failure so use > > debugfs_lookup() instead of checking for NULL. > [...] > > --- a/drivers/gpu/vga/vga_switcheroo.c > > +++ b/drivers/gpu/vga/vga_switcheroo.c > > @@ -914,7 +914,7 @@ static void vga_switcheroo_debugfs_fini(struct vgasr_priv *priv) > > static void vga_switcheroo_debugfs_init(struct vgasr_priv *priv) > > { > > /* already initialised */ > > - if (priv->debugfs_root) > > + if (debugfs_lookup("vgaswitcheroo", NULL)) > > return; > > > > priv->debugfs_root = debugfs_create_dir("vgaswitcheroo", NULL); > > If debugfs_create_dir() returns an error code, it does make sense to > retry the call when another vga_switcheroo client registers later. > I like that. > > However I'd prefer simply changing this to explicitly check for NULL, i.e.: > > - if (priv->debugfs_root) > + if (priv->debugfs_root == NULL) Apologies, I meant: - if (priv->debugfs_root) + if (priv->debugfs_root && !IS_ERR(priv->debugfs_root)) Thanks, Lukas > It's just as clear as calling debugfs_lookup() and it has way less > overhead. Granted, this isn't a hot path, but it's called on boot, > and the less code we execute, the faster the machine boots.
On 10/12/2021 8:48 AM, Lukas Wunner wrote: > On Mon, Oct 11, 2021 at 10:24:29PM +0200, Lukas Wunner wrote: >> On Mon, Oct 11, 2021 at 09:06:07PM +0200, Nirmoy Das wrote: >>> Debugfs APIs returns encoded error on failure so use >>> debugfs_lookup() instead of checking for NULL. >> [...] >>> --- a/drivers/gpu/vga/vga_switcheroo.c >>> +++ b/drivers/gpu/vga/vga_switcheroo.c >>> @@ -914,7 +914,7 @@ static void vga_switcheroo_debugfs_fini(struct vgasr_priv *priv) >>> static void vga_switcheroo_debugfs_init(struct vgasr_priv *priv) >>> { >>> /* already initialised */ >>> - if (priv->debugfs_root) >>> + if (debugfs_lookup("vgaswitcheroo", NULL)) >>> return; >>> >>> priv->debugfs_root = debugfs_create_dir("vgaswitcheroo", NULL); >> If debugfs_create_dir() returns an error code, it does make sense to >> retry the call when another vga_switcheroo client registers later. >> I like that. >> >> However I'd prefer simply changing this to explicitly check for NULL, i.e.: >> >> - if (priv->debugfs_root) >> + if (priv->debugfs_root == NULL) > Apologies, I meant: > > - if (priv->debugfs_root) > + if (priv->debugfs_root && !IS_ERR(priv->debugfs_root)) Thanks for the suggestion, Lukas. I will update that and resend. Nirmoy > Thanks, > > Lukas > >> It's just as clear as calling debugfs_lookup() and it has way less >> overhead. Granted, this isn't a hot path, but it's called on boot, >> and the less code we execute, the faster the machine boots.
diff --git a/drivers/gpu/vga/vga_switcheroo.c b/drivers/gpu/vga/vga_switcheroo.c index 365e6ddbe90f..a331525f0b32 100644 --- a/drivers/gpu/vga/vga_switcheroo.c +++ b/drivers/gpu/vga/vga_switcheroo.c @@ -914,7 +914,7 @@ static void vga_switcheroo_debugfs_fini(struct vgasr_priv *priv) static void vga_switcheroo_debugfs_init(struct vgasr_priv *priv) { /* already initialised */ - if (priv->debugfs_root) + if (debugfs_lookup("vgaswitcheroo", NULL)) return; priv->debugfs_root = debugfs_create_dir("vgaswitcheroo", NULL);
Debugfs APIs returns encoded error on failure so use debugfs_lookup() instead of checking for NULL. CC: Lukas Wunner <lukas@wunner.de> CC: David Airlie <airlied@linux.ie> CC: Daniel Vetter <daniel@ffwll.ch> CC: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> CC: Maxime Ripard <mripard@kernel.org> CC: Thomas Zimmermann <tzimmermann@suse.de> Signed-off-by: Nirmoy Das <nirmoy.das@amd.com> --- drivers/gpu/vga/vga_switcheroo.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) -- 2.32.0