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

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Message-ID: <Y8bjXjKiC/OSlppQ@kroah.com>
Date:   Tue, 17 Jan 2023 19:05:18 +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, Jan 13, 2023 at 06:40:04PM +0100, Uwe Kleine-König wrote:
> On Fri, Jan 13, 2023 at 12:43:39PM +0100, Greg Kroah-Hartman wrote:
> > On Thu, Jan 12, 2023 at 09:20:29AM +0100, Uwe Kleine-König wrote:
> > > Hello Greg,
> > > 
> > > On Fri, Dec 09, 2022 at 05:15:42PM +0100, Greg Kroah-Hartman wrote:
> > > > On Fri, Dec 09, 2022 at 04:52:07PM +0100, Uwe Kleine-König wrote:
> > > > > 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.
> > > 
> > > We're at v6.2-rc3 now. Is this patch still in your queue and you didn't
> > > come around yet to apply it, or did it fell through the cracks?
> > 
> > My queue is huge right now.
> > 
> > I'll work on this "soon".  Do you want this on a tag that others can
> > pull into their trees, or just in my normal driver-core-next branch?
> > Either is fine for me.
> 
> In my experience maintainers stumble when patches depend on patches that
> are not in -rc1. So I will be patient until this hits an -rc1. Thanks
> for the offer.

Fair enough, now added to my tree, sorry for the delay.  Feel free to
start flooding me with these types of changes, I'll be glad to take them
through my tree if at all possible.

greg k-h