linux-kernel - Re: [PATCH v2 6/9] debugfs: Implement debugfs_create

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Date:   Fri, 26 Mar 2021 15:12:35 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:     Greg KH <greg@...ah.com>, mingo@...nel.org, mgorman@...e.de,
        juri.lelli@...hat.com, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        bristot@...hat.com, joshdon@...gle.com, valentin.schneider@....com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 6/9] debugfs: Implement debugfs_create_str()

On Fri, Mar 26, 2021 at 02:10:41PM +0100, Rasmus Villemoes wrote:
> On 26/03/2021 13.57, Greg KH wrote:
> > On Fri, Mar 26, 2021 at 01:53:59PM +0100, Rasmus Villemoes wrote:
> >> On 26/03/2021 12.38, Peter Zijlstra wrote:
> >>
> >>> Implement debugfs_create_str() to easily display names and such in
> >>> debugfs.
> >>
> >> Patches 7-9 don't seem to add any users of this. What's it for precisely?
> > 
> > It's used in patch 7, look close :)
> 
> Ah, macrology. But the write capability doesn't seem used, and I (still)
> fail to see how that could be useful.

Correct, it isn't used. But I didn't think it would be acceptible to
not implement the write side. OTOH, if Greg would be okay with it, I can
change it to:

ssize_t debugfs_write_file_str(struct file *file, const char __user *user_buf,
                               size_t count, loff_t *ppos)
{
        /* This is really only for read-only strings */
        return -EINVAL;
}
EXPORT_SYMBOL_GPL(debugfs_write_file_str);

That's certianly simpler.