Subject: Re: [PATCH] bus: Make remove callback return void

From: Cornelia Huck <[email-masked]>
Date: Tue, 06 Jul 2021 13:17:37 +0200

On Tue, Jul 06 2021, Cornelia Huck <[email-masked]> wrote:

> On Tue, Jul 06 2021, Uwe Kleine-König <[email-masked]> 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 <[email-masked]>
>> ---
>> 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/[email-masked].
>>
>> 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;
 	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);
 	sch->driver = NULL;
-	return ret;
 }
 
 static void css_shutdown(struct device *dev)
diff --git a/drivers/s390/cio/device.c b/drivers/s390/cio/device.c
index 84f659cafe76..61d5d55bd9c8 100644
--- a/drivers/s390/cio/device.c
+++ b/drivers/s390/cio/device.c
@@ -1742,7 +1742,7 @@ ccw_device_probe (struct device *dev)
 	return 0;
 }
 
-static int ccw_device_remove(struct device *dev)
+static void ccw_device_remove(struct device *dev)
 {
 	struct ccw_device *cdev = to_ccwdev(dev);
 	struct ccw_driver *cdrv = cdev->drv;
@@ -1776,8 +1776,6 @@ static int ccw_device_remove(struct device *dev)
 	spin_unlock_irq(cdev->ccwlock);
 	io_subchannel_quiesce(sch);
 	__disable_cmf(cdev);
-
-	return 0;
 }
 
 static void ccw_device_shutdown(struct device *dev)
diff --git a/drivers/s390/cio/scm.c b/drivers/s390/cio/scm.c
index 9f26d4310bb3..b6b4589c70bd 100644
--- a/drivers/s390/cio/scm.c
+++ b/drivers/s390/cio/scm.c
@@ -28,12 +28,13 @@ static int scmdev_probe(struct device *dev)
 	return scmdrv->probe ? scmdrv->probe(scmdev) : -ENODEV;
 }
 
-static int scmdev_remove(struct device *dev)
+static void scmdev_remove(struct device *dev)
 {
 	struct scm_device *scmdev = to_scm_dev(dev);
 	struct scm_driver *scmdrv = to_scm_drv(dev->driver);
 
-	return scmdrv->remove ? scmdrv->remove(scmdev) : -ENODEV;
+	if (scmdrv->remove)
+		scmdrv->remove(scmdev);
 }
 
 static int scmdev_uevent(struct device *dev, struct kobj_uevent_env *env)
diff --git a/drivers/s390/crypto/ap_bus.c b/drivers/s390/crypto/ap_bus.c
index d2560186d771..8a0d37c0e2a5 100644
--- a/drivers/s390/crypto/ap_bus.c
+++ b/drivers/s390/crypto/ap_bus.c
@@ -884,7 +884,7 @@ static int ap_device_probe(struct device *dev)
 	return rc;
 }
 
-static int ap_device_remove(struct device *dev)
+static void ap_device_remove(struct device *dev)
 {
 	struct ap_device *ap_dev = to_ap_dev(dev);
 	struct ap_driver *ap_drv = ap_dev->drv;
@@ -909,8 +909,6 @@ static int ap_device_remove(struct device *dev)
 	ap_dev->drv = NULL;
 
 	put_device(dev);
-
-	return 0;
 }
 
 struct ap_queue *ap_get_qdev(ap_qid_t qid)