linux-kernel - Re: Proposal for a new checkpatch check; matching _set_drvdata() & _get

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Date:   Thu, 19 Nov 2020 16:11:11 -0800
From:   Joe Perches <joe@...ches.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Alexandru Ardelean <ardeleanalex@...il.com>
Cc:     Robo Bot <apw@...onical.com>, LKML <linux-kernel@...r.kernel.org>,
        Alexandru Ardelean <alexandru.ardelean@...log.com>,
        Julia Lawall <julia.lawall@...6.fr>,
        cocci <cocci@...teme.lip6.fr>
Subject: Re: Proposal for a new checkpatch check; matching _set_drvdata() &
 _get_drvdata()

On Thu, 2020-11-19 at 17:16 +0200, Andy Shevchenko wrote:
> On Thu, Nov 19, 2020 at 4:09 PM Alexandru Ardelean
> <ardeleanalex@...il.com> wrote:
> > 
> > Hey,
> > 
> > So, I stumbled on a new check that could be added to checkpatch.
> > Since it's in Perl, I'm reluctant to try it.
> > 
> > Seems many drivers got to a point where they now call (let's say)
> > spi_set_drvdata(), but never access that information via
> > spi_get_drvdata().
> > Reasons for this seem to be:
> > 1. They got converted to device-managed functions and there is no
> > longer a remove hook to require the _get_drvdata() access
> > 2. They look like they were copied from a driver that had a
> > _set_drvdata() and when the code got finalized, the _set_drvdata() was
> > omitted
> > 
> > There are a few false positives that I can notice at a quick look,
> > like the data being set via some xxx_set_drvdata() and retrieved via a
> > dev_get_drvdata().
> 
> I can say quite a few. And this makes a difference.
> So, basically all drivers that are using PM callbacks would rather use
> dev_get_drvdata() rather than bus specific.
> 
> > I think checkpatch reporting these as well would be acceptable simply
> > from a reviewability perspective.
> > 
> > I did a shell script to quickly check these. See below.
> > It's pretty badly written but it is enough for me to gather a list.
> > And I wrote it in 5 minutes :P
> > I initially noticed this in some IIO drivers, and then I suspected
> > that this may be more widespread.
> 
> It seems more suitable for coccinelle.

To me as well.