[PATCH 4/4] vgaswitcheroo: do not check for NULL debugfs dentry

[Das, Nirmoy]

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.