[1/3] spi: fix resource leak for drivers without .remove callback

Consider an spi driver with a .probe but without a .remove callback (e.g.
rtc-ds1347). The function spi_drv_probe() is called to bind a device and
so some init routines like dev_pm_domain_attach() are used. As there is
no remove callback spi_drv_remove() isn't called at unbind time however
and so calling dev_pm_domain_detach() is missed and the pm domain keeps
active.

To fix this always use either both or none of the functions and make
them handle the callback not being set.

Fixes: 33cf00e57082 ("spi: attach/detach SPI device to the ACPI power domain")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
---
 drivers/spi/spi.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)


base-commit: 09162bc32c880a791c6c0668ce0745cf7958f576
prerequisite-patch-id: 81a6cc3e9e110aa4427c029e2f950f83a91c9a22
prerequisite-patch-id: 9c80bf49810461fd0e1a35b0a134675bc4333678
prerequisite-patch-id: bfb025de56c9e52ea068686a64f5f5ed6b29ab4f
prerequisite-patch-id: b490ddb3c51a92f058e252faf89c4cadd4a0e415
prerequisite-patch-id: 9c94ab8c9f66d0330549d1ecdc18e6ac97f8a7e4

On Thu, Nov 19, 2020 at 03:24:16PM +0000, Mark Brown wrote:
> On Thu, Nov 19, 2020 at 04:20:57PM +0100, Uwe Kleine-König wrote:
> > Consider an spi driver with a .probe but without a .remove callback (e.g.
> > rtc-ds1347). The function spi_drv_probe() is called to bind a device and
> > so some init routines like dev_pm_domain_attach() are used. As there is
> > no remove callback spi_drv_remove() isn't called at unbind time however
> > and so calling dev_pm_domain_detach() is missed and the pm domain keeps
> > active.
> 
> > To fix this always use either both or none of the functions and make
> > them handle the callback not being set.
> 
> Why would we want to tie configuring PM domains to either of these
> functions?  We certainly don't want to force drivers to have empty
> remove functions to trigger cleanup of domains, this would be
> counterintuitive and this stuff should be transparent to the driver.

Yes, I thought that this is not the final fix. I just sent the minimal
change to prevent the imbalance. So if I understand correctly, I will
have to respin with the following squashed into patch 1:

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 5bdc66f08ee1..5becf6c2c409 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -445,10 +445,8 @@ int __spi_register_driver(struct module *owner, struct spi_driver *sdrv)
 {
 	sdrv->driver.owner = owner;
 	sdrv->driver.bus = &spi_bus_type;
-	if (sdrv->probe || sdrv->remove) {
-		sdrv->driver.probe = spi_drv_probe;
-		sdrv->driver.remove = spi_drv_remove;
-	}
+	sdrv->driver.probe = spi_drv_probe;
+	sdrv->driver.remove = spi_drv_remove;
 	if (sdrv->shutdown)
 		sdrv->driver.shutdown = spi_drv_shutdown;
 	return driver_register(&sdrv->driver);

(Not sure this makes a difference in real life, are there drivers
without a .probe callback?)

Best regards
Uwe

Hello Mark,

On Thu, Nov 19, 2020 at 03:41:39PM +0000, Mark Brown wrote:
> On Thu, Nov 19, 2020 at 04:35:40PM +0100, Uwe Kleine-König wrote:
> 
> > Yes, I thought that this is not the final fix. I just sent the minimal
> > change to prevent the imbalance. So if I understand correctly, I will
> > have to respin with the following squashed into patch 1:
> 
> > -	if (sdrv->probe || sdrv->remove) {
> > -		sdrv->driver.probe = spi_drv_probe;
> > -		sdrv->driver.remove = spi_drv_remove;
> > -	}
> > +	sdrv->driver.probe = spi_drv_probe;
> > +	sdrv->driver.remove = spi_drv_remove;
> >  	if (sdrv->shutdown)
> >  		sdrv->driver.shutdown = spi_drv_shutdown;
> >  	return driver_register(&sdrv->driver);
> 
> I think so, I'd need to see the full patch to check of course.

ok.
 
> > (Not sure this makes a difference in real life, are there drivers
> > without a .probe callback?)
> 
> Your changelog seemed to say that it would make remove mandatory.

No, that's not what the patch did. It made unconditional use of
spi_drv_remove(), but an spi_driver without .remove() was still ok. I
will reword to make this clearer.

Best regards
Uwe