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Date: Sat, 4 Feb 2017 19:10:58 +0100 (CET)
From: Julia Lawall <julia.lawall@lip6.fr>
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To: Joe Perches <joe@perches.com>
cc: Guenter Roeck <linux@roeck-us.net>, Derek Robson <robsonde@gmail.com>,
        Julia Lawall <julia.lawall@lip6.fr>, w.d.hubbs@gmail.com,
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        speakup@linux-speakup.org, devel@driverdev.osuosl.org,
        linux-kernel@vger.kernel.org
Subject: Re: Staging: speakup - syle fix permissions to octal
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On Fri, 3 Feb 2017, Joe Perches wrote:

> (adding Julia Lawall)
>
> On Fri, 2017-02-03 at 20:44 -0800, Guenter Roeck wrote:
> > On Sat, Jan 28, 2017 at 07:05:09PM +1300, Derek Robson wrote:
> > > A style fix across whole driver.
> > > changed permissions to octal style, found using checkpatch
> > >
> > > Signed-off-by: Derek Robson <robsonde@gmail.com>
> >
> > FWIW, I think changes like this are best done using coccinelle.
>
> I think checkpatch does it reasonably well.
>
> Julia?  Can coccinelle do this?
>
> I believe cocinelle doesn't handle the substitution
> and octal addition very well when multiple flags
> are used.

OK, finally received.  I think that Guenter's solution is a good one,
because the rule-writer knows better than Coccinelle what people find to
be intelligible.

julia

>
> > That ensures that the results can be reproduced and are well defined.
> > As it is, someone will have to check each line of your patches to ensure
> > that the conversion is correct.
> >
> > It would also ensure (hopefully) that we don't end up with constructs
> > such as
> >
> > > -#define USER_R (S_IFREG|S_IRUGO)
> > > -#define USER_W (S_IFREG|S_IWUGO)
> > > +#define USER_R (S_IFREG|0444)
> > > +#define USER_W (S_IFREG|0666)
> >
> > which really defeat the purpose of the whole exercise.
>
> Why do you think mixing file specific attributes
> with octal permissions is a bad thing?
>
> $ git log -1 f90774e1fd2700d
> commit f90774e1fd2700de4a6e0d62866d34a26c544bd0
> Author: Joe Perches <joe@perches.com>
> Date:   Tue Oct 11 13:51:47 2016 -0700
>
>     checkpatch: look for symbolic permissions and suggest octal instead
>
>     S_<FOO> uses should be avoided where octal is more intelligible.
>
>     Linus didst say:
>
>     : It's *much* easier to parse and understand the octal numbers, while the
>     : symbolic macro names are just random line noise and hard as hell to
>     : understand.  You really have to think about it.
>     :
>     : So we should rather go the other way: convert existing bad symbolic
>     : permission bit macro use to just use the octal numbers.
>     :
>     : The symbolic names are good for the *other* bits (ie sticky bit, and the
>     : inode mode _type_ numbers etc), but for the permission bits, the symbolic
>     : names are just insane crap.  Nobody sane should ever use them.  Not in the
>     : kernel, not in user space.
>     (http://lkml.kernel.org/r/CA+55aFw5v23T-zvDZp-MmD_EYxF8WbafwwB59934FV7g21uMGQ@mail.gmail.com)
>
>     Link: http://lkml.kernel.org/r/7232ef011d05a92f4caa86a5e9830d87966a2eaf.1470180926.git.joe@perches.com
>     Signed-off-by: Joe Perches <joe@perches.com>
>     Cc: Linus Torvalds <torvalds@linux-foundation.org>
>     Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
>     Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
>