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Date:   Fri, 20 Nov 2020 13:58:52 +0200
From:   Alexandru Ardelean <ardeleanalex@...il.com>
To:     Julia Lawall <julia.lawall@...ia.fr>
Cc:     Joe Perches <joe@...ches.com>,
        Andy Shevchenko <andy.shevchenko@...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 Fri, Nov 20, 2020 at 1:57 PM Julia Lawall <julia.lawall@...ia.fr> wrote:
>
>
>
> On Fri, 20 Nov 2020, Alexandru Ardelean wrote:
>
> > On Fri, Nov 20, 2020 at 12:47 PM Julia Lawall <julia.lawall@...ia.fr> wrote:
> > >
> > >
> > >
> > > 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?
> >
> > Ah, it's a stupid script I wrote in 5 minutes, so I did not bother to
> > make things smart.
> > In the text-matching I did in shell, there are some entries that come
> > from comments and docs.
> > It's only about 3-4 entries, so I just did a visual/manual ignore.
> >
> > In essence:
> > The script searches for all strings that contain _set_drvdata.
> > The separators are whitespace.
> > It creates a list of all  xxxx_set_drvdata functions.
> > For each xxxx_set_drvdata function:
> >     It checks all files that have a xxxx_set_drvdata entry, but no
> > xxxx_get_drvdata
>
> OK, but I have the impression that you want to ignore pci_set_drvdata for
> some reason?  Or did I misunderstand?

Yes. See difficultly visible double quote :P
'  "pci_set_drvdata   '
Apologies for the confusion

        if [ "$fn" == '"pci_set_drvdata' ] ; then
                continue
        fi


>
> julia
>
> >
> > I piped this output into a file and started manually checking the drivers.
> > There is one [I forget which function] that is xxxx_set_drvdata() but
> > equivalent is xxxx_drvdata()
> >
> > As Andy said, some precautions must be taken in places where
> > xxxx_set_drvdata() is called but dev_get_drvdata() is used.
> > Cases like PM suspend/resume calls.
> > And there may be some cases outside this context.
> >
> >
> > >
> > > julia
> >

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