linux-kernel - Re: [PATCH v2 1/2] include: linux: sysfs: Add __ATTR

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Date:   Tue, 19 Sep 2017 14:13:40 +0200
From:   Lars-Peter Clausen <lars@...afoo.de>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Jonathan Cameron <jic23@...nel.org>, devel@...verdev.osuosl.org,
        daniel.baluta@...il.com, pmeerw@...erw.net,
        Michael.Hennerich@...log.com, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org, nick.desaulniers@...il.com,
        outreachy-kernel@...glegroups.com,
        Himanshi Jain <himshijain.hj@...il.com>, knaack.h@....de
Subject: Re: [PATCH v2 1/2] include: linux: sysfs: Add __ATTR_NAMED macro

On 09/13/2017 11:29 PM, Greg KH wrote:
> On Wed, Sep 13, 2017 at 09:23:31PM +0200, Lars-Peter Clausen wrote:
>> On 09/13/2017 08:58 PM, Greg KH wrote:
>>> On Wed, Sep 13, 2017 at 06:03:10PM +0100, Jonathan Cameron wrote:
>>>> On Wed, 13 Sep 2017 14:14:07 +0530
>>>> Himanshi Jain <himshijain.hj@...il.com> wrote:
>>>>
>>>>> Add __ATTR_NAMED macro similar to __ATTR but taking name as a
>>>>> string instead of implicit conversion of argument to string using
>>>>> the macro _stringify(_name).
>>>>>
>>>>> Signed-off-by: Himanshi Jain <himshijain.hj@...il.com>
>>>>> ---
>>>>>  include/linux/sysfs.h | 7 +++++++
>>>>>  1 file changed, 7 insertions(+)
>>>>>
>>>>> diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
>>>>> index aa02c32..20321cf 100644
>>>>> --- a/include/linux/sysfs.h
>>>>> +++ b/include/linux/sysfs.h
>>>>> @@ -104,6 +104,13 @@ struct attribute_group {
>>>>>  	.store	= _store,						\
>>>>>  }
>>>>>  
>>>>> +#define __ATTR_NAMED(_name, _mode, _show, _store) {			\
>>>>
>>>> I'm not sure about the naming here.  The normal __ATTR macro is also
>>>> 'named'.  Maybe something as awful as
>>>>
>>>> __ATTR_STRING_NAME ? 
>>>>
>>>> Greg what do you think?
>>>
>>> ick ick ick.
>>>
>>>> This is all to allow us to have names with operators in them without
>>>> checkpatch complaining about them... A worthwhile aim just to stop
>>>> more people wasting time trying to 'fix' those cases by adding spaces.
>>>
>>> Yeah, but this really seems "heavy" for just a crazy sysfs name in a
>>> macro.  Adding a whole new "core" define for that is a hard sell...
>>>
>>> I also want to get rid of the "generic" __ATTR type macros, and force
>>> people to use the proper _RW and friends instead.  I don't want to add
>>> another new one that people will start to use that I later have to
>>> change...
>>>
>>> So no, I don't like this, how about just changing your macros instead?
>>> No one else has this problem :)
>>
>> Nobody else realized they have this problem yet. E.g. there are a few users
>> of __ATTR in block/genhd.c that have the same issue and are likely to
>> generate the same false positives from static checkers.
> 
> Then fix the broken static checkers :)

The static checkers aren't broken, the macro is. It takes a string
parameter, but instead of a string it is passed as an expression and then
transformed to string using preprocessor magic in the macro. That's not very
good semantics. And hence this gets detected as a false positive, because
nobody expects such strange behavior.