Re: [PATCH] arm: mach-tegra: check wether we have debugfs enabled or not

[Russell King - ARM Linux <linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org>]

On Wed, Oct 17, 2012 at 03:22:13PM -0600, Stephen Warren wrote:
> On 10/17/2012 02:12 PM, Russell King - ARM Linux wrote:
> > On Wed, Oct 17, 2012 at 03:13:16PM -0400, Devendra Naga wrote:
> >> if debugfs is not enabled in kernel it returns -ENODEV, check it
> >> with IS_ERR_OR_NULL along with the null return if it fails to
> >> create a file in debugfs.
> >>
> >> Signed-off-by: Devendra Naga <devendra.aaru-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> >> ---
> >>  arch/arm/mach-tegra/powergate.c |    2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/arch/arm/mach-tegra/powergate.c b/arch/arm/mach-tegra/powergate.c
> >> index de0662d..1809b91d 100644
> >> --- a/arch/arm/mach-tegra/powergate.c
> >> +++ b/arch/arm/mach-tegra/powergate.c
> >> @@ -269,7 +269,7 @@ int __init tegra_powergate_debugfs_init(void)
> >>  	if (powergate_name) {
> >>  		d = debugfs_create_file("powergate", S_IRUGO, NULL, NULL,
> >>  			&powergate_fops);
> >> -		if (!d)
> >> +		if (IS_ERR_OR_NULL(d))
> >>  			return -ENOMEM;
> > 
> > So, you want to make this function hard-fail if a debugfs error occurs
> > _or_ debugfs is not configured?  That doesn't seem to be a clever thing
> > to do.
> 
> In practice, that quoted chunk of code is inside an #ifdef
> CONFIG_DEBUG_FS, so according to the documentation for
> debugfs_create_file(), the IS_ERR case of IS_ERR_OR_NULL cannot happen
> here. So, the above change is a no-op, so there's not much point
> applying it.

Ok.  Another reason not to apply it is that should the ifdefs get
removed, it'll start failing when debugfs is disabled with -ENOMEM,
which isn't bright.  A further reason is it's another place that'd
need reviewing for bad usage of the IS_ERR_OR_NULL() problem I've
pointed out this evening.