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

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Date:   Fri, 20 Nov 2020 11:47:15 +0100 (CET)
From:   Julia Lawall <julia.lawall@...ia.fr>
To:     Joe Perches <joe@...ches.com>
cc:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Alexandru Ardelean <ardeleanalex@...il.com>,
        Robo Bot <apw@...onical.com>,
        Alexandru Ardelean <alexandru.ardelean@...log.com>,
        LKML <linux-kernel@...r.kernel.org>,
        cocci <cocci@...teme.lip6.fr>
Subject: Re: [Cocci] Proposal for a new checkpatch check; matching _set_drvdata()
 & _get_drvdata()



On Thu, 19 Nov 2020, Joe Perches wrote:

> 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.

To me as well, since it seems to involve nonlocal information.

I'm not sure to understand the original shell script. Is there
something interesting about pci_set_drvdata?

julia