linux-kernel - Re: Staging: speakup - syle fix permissions to octal

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Message-ID: <1486193266.22276.82.camel@perches.com>
Date:   Fri, 03 Feb 2017 23:27:46 -0800
From:   Joe Perches <joe@...ches.com>
To:     Guenter Roeck <linux@...ck-us.net>,
        Derek Robson <robsonde@...il.com>,
        Julia Lawall <julia.lawall@...6.fr>
Cc:     w.d.hubbs@...il.com, chris@...-brannons.com, kirk@...sers.ca,
        samuel.thibault@...-lyon.org, gregkh@...uxfoundation.org,
        shraddha.6596@...il.com, alan@...ux.intel.com, shiva@...ev.nl,
        amitoj1606@...il.com, amsfield22@...il.com, bhumirks@...il.com,
        waltfeasel@...il.com, speakup@...ux-speakup.org,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: Staging: speakup - syle fix permissions to octal

(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@...il.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.

> 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@...ches.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@...ches.com>
    Cc: Linus Torvalds <torvalds@...ux-foundation.org>
    Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>