linux-kernel - Re: [PATCH] platform: Provide a remove callback that returns no value

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Date:   Fri, 9 Dec 2022 17:15:42 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
Cc:     linux-kernel@...r.kernel.org, kernel@...gutronix.de,
        "Rafael J. Wysocki" <rafael@...nel.org>
Subject: Re: [PATCH] platform: Provide a remove callback that returns no value

On Fri, Dec 09, 2022 at 04:52:07PM +0100, Uwe Kleine-König wrote:
> Hello Greg,
> 
> On Fri, Dec 09, 2022 at 04:21:30PM +0100, Greg Kroah-Hartman wrote:
> > On Fri, Dec 09, 2022 at 04:09:14PM +0100, Uwe Kleine-König wrote:
> > > struct platform_driver::remove returning an integer made driver authors
> > > expect that returning an error code was proper error handling. However
> > > the driver core ignores the error and continues to remove the device
> > > because there is nothing the core could do anyhow and reentering the
> > > remove callback again is only calling for trouble.
> > > 
> > > So this is an source for errors typically yielding resource leaks in the
> > > error path.
> > > 
> > > As there are too many platform drivers to neatly convert them all to
> > > return void in a single go, do it in several steps after this patch:
> > > 
> > >  a) Convert all drivers to implement .remove_new() returning void instead
> > >     of .remove() returning int;
> > >  b) Change struct platform_driver::remove() to return void and so make
> > >     it identical to .remove_new();
> > >  c) Change all drivers back to .remove() now with the better prototype;
> > 
> > Change c) seems like it will be just as much work as a), right?
> 
> Yeah, but c) should be trivially doable per subsystem using coccinelle.
> So my plan is to do a) per subsystem with one patch per driver and c)
> with one patch per subsystem.
> 
> > Who is going to do the work of the conversion to this new prototype?
> > I'll be glad to take this, but I don't want to see a half-finished
> > conversion happen and us stuck with a "new" and "old" call, as that
> > would just be a mess.
> 
> The idea is that this becomes my new pet project once 
> https://lore.kernel.org/lkml/20221118224540.619276-1-uwe@kleine-koenig.org
> is complete. :-)
> 
> I intend to work on that once the patch under discussion is included in
> an -rc1.

Ok, I'll wait to queue this up to my tree until after 6.2-rc1 is out,
thanks.

greg k-h