linux-kernel - Re: [PATCH 2/2] intel_pmc_core: avoid boot time warning for !CONFIG_DEBUGFS

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Message-ID: <20161012081318.GA4411@f23x64.localdomain>
Date:   Wed, 12 Oct 2016 01:13:18 -0700
From:   Darren Hart <dvhart@...radead.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rajneesh Bhardwaj <rajneesh.bhardwaj@...el.com>,
        Darren Hart <dvhart@...ux.intel.com>,
        Nicolai Stange <nicstange@...il.com>,
        Vishwanath Somayaji <vishwanath.somayaji@...el.com>,
        platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] intel_pmc_core: avoid boot time warning for
 !CONFIG_DEBUGFS_FS

On Mon, Oct 10, 2016 at 02:29:17PM +0200, Greg Kroah-Hartman wrote:
> On Mon, Oct 10, 2016 at 01:12:58PM +0200, Arnd Bergmann wrote:
> > While looking at a patch that introduced a compile-time warning
> > "‘pmc_core_dev_state_get’ defined but not used" (I sent a patch
> > for debugfs to fix it), I noticed that the same patch caused
> > it in intel_pmc_core also introduced a bogus run-time warning:
> > "PMC Core: debugfs register failed".
> > 
> > The problem is the IS_ERR_OR_NULL() check that as usual gets
> > things wrong: when CONFIG_DEBUGFS_FS is disabled,
> > debugfs_create_dir() fails with an error code, and we don't
> > need to warn about it, unlike the case in which it returns
> > NULL.
> > 
> > This reverts the driver to the previous state of not warning
> > about CONFIG_DEBUGFS_FS being disabled. I chose not to
> > restore the driver to making a runtime error in debugfs
> > fatal in pmc_core_probe().
> > 
> > Fixes: df2294fb6428 ("intel_pmc_core: Convert to DEFINE_DEBUGFS_ATTRIBUTE")
> > Signed-off-by: Arnd Bergmann <arnd@...db.de>
> > ---
> >  drivers/platform/x86/intel_pmc_core.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/platform/x86/intel_pmc_core.c b/drivers/platform/x86/intel_pmc_core.c
> > index 520b58a04daa..e8b1b836ca2d 100644
> > --- a/drivers/platform/x86/intel_pmc_core.c
> > +++ b/drivers/platform/x86/intel_pmc_core.c
> > @@ -100,7 +100,7 @@ static int pmc_core_dbgfs_register(struct pmc_dev *pmcdev)
> >  	struct dentry *dir, *file;
> >  
> >  	dir = debugfs_create_dir("pmc_core", NULL);
> > -	if (IS_ERR_OR_NULL(dir))
> > +	if (!dir)
> >  		return -ENOMEM;
> 
> Hah, no, you shouldn't ever care about any return value being "wrong"
> from debugfs, the code should just continue on as normal.
> 
> And yes, you are correct, the IS_ERR_OR_NULL() is totally wrong.
> 
> thanks,
> 
> greg k-h
> 

Thanks Arnd and Greg, appreciate the catch and the fix.

Applied.

-- 
Darren Hart
Intel Open Source Technology Center