Re: [PATCH] bus: Make remove callback return void - Uwe Kleine-König

From: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
To: Cornelia Huck <cohuck@redhat.com>
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Subject: Re: [PATCH] bus: Make remove callback return void
Date: Tue, 6 Jul 2021 14:14:45 +0200	[thread overview]
Message-ID: <20210706121445.o3nxgi4bhzrw5w73@pengutronix.de> (raw)
In-Reply-To: <87mtqzhesu.fsf@redhat.com>

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On Tue, Jul 06, 2021 at 01:17:37PM +0200, Cornelia Huck wrote:
> On Tue, Jul 06 2021, Cornelia Huck <cohuck@redhat.com> wrote:
> 
> > On Tue, Jul 06 2021, Uwe Kleine-König <u.kleine-koenig@pengutronix.de> wrote:
> >
> >> The driver core ignores the return value of this callback because there
> >> is only little it can do when a device disappears.
> >>
> >> This is the final bit of a long lasting cleanup quest where several
> >> buses were converted to also return void from their remove callback.
> >> Additionally some resource leaks were fixed that were caused by drivers
> >> returning an error code in the expectation that the driver won't go
> >> away.
> >>
> >> With struct bus_type::remove returning void it's prevented that newly
> >> implemented buses return an ignored error code and so don't anticipate
> >> wrong expectations for driver authors.
> >
> > Yay!
> >
> >>
> >> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> >> ---
> >> Hello,
> >>
> >> this patch depends on "PCI: endpoint: Make struct pci_epf_driver::remove
> >> return void" that is not yet applied, see
> >> https://lore.kernel.org/r/20210223090757.57604-1-u.kleine-koenig@pengutronix.de.
> >>
> >> I tested it using allmodconfig on amd64 and arm, but I wouldn't be
> >> surprised if I still missed to convert a driver. So it would be great to
> >> get this into next early after the merge window closes.
> >
> > I'm afraid you missed the s390-specific busses in drivers/s390/cio/
> > (css/ccw/ccwgroup).

:-\

> The change for vfio/mdev looks good.
> 
> The following should do the trick for s390; not sure if other
> architectures have easy-to-miss busses as well.
> 
> diff --git a/drivers/s390/cio/ccwgroup.c b/drivers/s390/cio/ccwgroup.c
> index 9748165e08e9..a66f416138ab 100644
> --- a/drivers/s390/cio/ccwgroup.c
> +++ b/drivers/s390/cio/ccwgroup.c
> @@ -439,17 +439,15 @@ module_exit(cleanup_ccwgroup);
>  
>  /************************** driver stuff ******************************/
>  
> -static int ccwgroup_remove(struct device *dev)
> +static void ccwgroup_remove(struct device *dev)
>  {
>  	struct ccwgroup_device *gdev = to_ccwgroupdev(dev);
>  	struct ccwgroup_driver *gdrv = to_ccwgroupdrv(dev->driver);
>  
>  	if (!dev->driver)
> -		return 0;
> +		return;

This is fine to be squashed into my patch. In the long run: in a remove
callback dev->driver cannot be NULL, so this if could go away.

>  	if (gdrv->remove)
>  		gdrv->remove(gdev);
> -
> -	return 0;
>  }
>  
>  static void ccwgroup_shutdown(struct device *dev)
> diff --git a/drivers/s390/cio/css.c b/drivers/s390/cio/css.c
> index a974943c27da..ebc321edba51 100644
> --- a/drivers/s390/cio/css.c
> +++ b/drivers/s390/cio/css.c
> @@ -1371,15 +1371,14 @@ static int css_probe(struct device *dev)
>  	return ret;
>  }
>  
> -static int css_remove(struct device *dev)
> +static void css_remove(struct device *dev)
>  {
>  	struct subchannel *sch;
> -	int ret;
>  
>  	sch = to_subchannel(dev);
> -	ret = sch->driver->remove ? sch->driver->remove(sch) : 0;
> +	if (sch->driver->remove)
> +		sch->driver->remove(sch);

Maybe the return type for this function pointer can be changed to void,
too.

I will add these changes to a v2 that I plan to send out after the dust
settles some more.

Thanks
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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