linux-kernel - Re: [PATCH v5 1/2] iommu - Enable debugfs exposure of IOMMU driver internals

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Date:   Tue, 8 May 2018 15:07:08 -0500
From:   Gary R Hook <gary.hook@....com>
To:     Joe Perches <joe@...ches.com>, "Hook, Gary" <ghook@....com>,
        kbuild test robot <lkp@...el.com>
Cc:     kbuild-all@...org, iommu@...ts.linux-foundation.org,
        joro@...tes.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 1/2] iommu - Enable debugfs exposure of IOMMU driver
 internals

On 05/08/2018 01:48 PM, Joe Perches wrote:
> On Tue, 2018-05-08 at 12:08 -0500, Hook, Gary wrote:
>> On 5/7/2018 6:47 PM, kbuild test robot wrote:
>>>
>>> All error/warnings (new ones prefixed by >>):
>>>
>>>      In file included from include/linux/intel-iommu.h:32:0,
>>>                       from drivers/gpu/drm/i915/i915_drv.h:41,
>>>                       from drivers/gpu/drm/i915/i915_oa_bxt.c:31:
>>>      include/linux/iommu.h: In function 'iommu_debugfs_new_driver_dir':
>>>>> include/linux/iommu.h:706:8: error: parameter name omitted
>>>
>>>       struct dentry *iommu_debugfs_new_driver_dir(char *) {};
>>>              ^~~~~~
>>>      In file included from include/linux/intel-iommu.h:32:0,
>>>                       from drivers/gpu/drm/i915/i915_drv.h:41,
>>>                       from drivers/gpu/drm/i915/i915_oa_bxt.c:31:
>>>>> include/linux/iommu.h:706:8: warning: control reaches end of non-void function [-Wreturn-type]
>>>
>>>       struct dentry *iommu_debugfs_new_driver_dir(char *) {};
>>>              ^~~~~~
>>>
>>> vim +706 include/linux/iommu.h
>>>
>>>      700	
>>>      701	#ifdef CONFIG_IOMMU_DEBUGFS
>>>      702	void iommu_debugfs_setup(void);
>>>      703	struct dentry *iommu_debugfs_new_driver_dir(char *);
>>>      704	#else
>>>      705	static inline void iommu_debugfs_setup(void) {}
>>>    > 706	struct dentry *iommu_debugfs_new_driver_dir(char *) {};
>>>      707	#endif
>>>      708	
>>
>> I have no problems with adding parameter names. But
>> scripts/checkpatch.pl doesn't seem to check for this, nor require it.
>> Should checkpatch be updated?
> 
> I'm pretty sure that's not feasible.

Ugh. This is a definition, not a declaration. My bad. Which is likely 
why I decided to apologize up front.

> And when the compiler tells you you've stuffed up some
> syntactical bit, why should checkpatch duplicate the
> output error message too?

Well, that's the point: neither the 4.8 nor 5.4 compiler complained 
about this. Not as an error, despite the fact that (now that I read what 
is actually here, as opposed to what I think is there) this is wrong. 
Had an error message been emitted, and the make stopped, I would have 
figure this out before embarrassing myself in front of the entire interwebs.

> btw:  That's an unnecessary ; at the end of that non-void
> function and it should probably be something like:

You are correct, sir. I've made a change on this.

> 
> static inline struct dentry *iommu_debugfs_new_driver_dir(char *dir)
> {
> 	return NULL;
> }

Thanks for taking a few moments to comment. Much appreciated.