Re: Proposal for a new checkpatch check; matching _set_drvdata() & _get_drvdata()

[Andy Shevchenko]

On Thu, Nov 19, 2020 at 4:09 PM Alexandru Ardelean
<ardeleanalex@xxxxxxxxx> 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.

> The shell script gathers a list of xxx_set_drvdata() functions then
> greps through all files and also checks if there are any matching
> xxx_get_drvdata().
>
> Thanks
> Alex
>
> Shell script:
> -----------------------------------------------------------------------
> #!/bin/bash
>
> fns1=$(git grep _set_drvdata | cut -d: -f2 | cut -d'(' -f1 | sort -u)
>
> for fn in $fns1 ; do
>         if [ "$fn" == "//pci_set_drvdata" ] ; then
>                 continue
>         fi
>         if [ "$fn" == '``dev_set_drvdata' ] ; then
>                 continue
>         fi
>         if [ "$fn" == '"pci_set_drvdata' ] ; then
>                 continue
>         fi
>         if [[ "$fn" == *"_set_drvdata" ]]; then
>                 fns2="$fns2 $fn"
>         fi
> done
>
> fns1=$(echo $fns2 | tr ' ' '\n' | sort -u | tr '\n' ' ')
>
> for fn in $fns1 ; do
>         get_fn=$(echo $fn | sed 's/_set_/_get_/g')
>
>         echo "Matching $fn - $get_fn"
>         for file in $(git grep $fn | cut -d: -f1 | sort -u) ; do
>                 if ! grep -q $get_fn $file ; then
>                         echo "   Maybe $file"
>                 fi
>         done
> done
> -----------------------------------------------------------------------

-- 
With Best Regards,
Andy Shevchenko