linux-kernel - Re: [PATCH v2 1/2] pinctrl: use to octal permissions for debugfs files

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Date:   Wed, 10 Feb 2021 13:21:15 -0800
From:   Drew Fustini <drew@...gleboard.org>
To:     Joe Perches <joe@...ches.com>
Cc:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Tony Lindgren <tony@...mide.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Pantelis Antoniou <pantelis.antoniou@...sulko.com>,
        Jason Kridner <jkridner@...gleboard.org>,
        Robert Nelson <robertcnelson@...gleboard.org>
Subject: Re: [PATCH v2 1/2] pinctrl: use to octal permissions for debugfs
 files

On Wed, Feb 10, 2021 at 04:36:00AM -0800, Joe Perches wrote:
> On Wed, 2021-02-10 at 12:18 +0200, Andy Shevchenko wrote:
> > On Wed, Feb 10, 2021 at 10:30 AM Joe Perches <joe@...ches.com> wrote:
> > > On Tue, 2021-02-09 at 23:49 -0800, Drew Fustini wrote:
> > 
> > > > -     debugfs_create_file("pinctrl-devices", S_IFREG | S_IRUGO,
> > > > +     debugfs_create_file("pinctrl-devices", 0400,
> > > >                           debugfs_root, NULL, &pinctrl_devices_fops);
> > > 
> > > NAK.  You've changed the permission levels.
> > 
> > NAK is usually given when the whole idea is broken. Here is not the
> > case and you may have helped to amend the patch.
> 
> NAK IMO just means the patch should not be applied, not that the
> concept is broken.
> 
> > ...
> > 
> > > And you have to keep the S_IFREG or'd along with the octal.
> > 
> > Perhaps time to read the code?
> > https://elixir.bootlin.com/linux/latest/source/fs/debugfs/inode.c#L387
> 
> Then the commit message is also broken.
> 
> > > checkpatch does this conversion using this command line:
> > > 
> > > $ ./scripts/checkpatch.pl -f --show-types --terse drivers/pinctrl/*.[ch] --types=SYMBOLIC_PERMS --fix-inplace
> > 
> > NAK! See above.
> 
> The command line above is for octal conversion of the symbolic permissions.
> 
> Any other conversion would be for a different purpose and that purpose and
> should be described in the commit message.
> 
> 

Thanks for review comments from all.

I will change from the incorrect 0400 to 0444.

As for S_IFREG, it does seem like leaving off S_IFREG is the most common
case when using octal permissions with debugfs_create_*():

$ git grep debugfs_create drivers/ |grep 0444 |grep -v S_IFREG | wc -l
302
$ git grep debugfs_create drivers/ |grep 0444 |grep S_IFREG | wc -l
9

As noted by Andy, this is okay as the S_IFREG flag is added to the mode
__debugfs_create_file() inside fs/debugfs/inode.c. I will note this in
the commit message.

Thank you,
Drew