Commit fde25a9b authored by Alan Stern's avatar Alan Stern Committed by Greg Kroah-Hartman
Browse files

Driver core: driver_find() drops reference before returning 



As part of the removal of get_driver()/put_driver(), this patch
(as1510) changes driver_find(); it now drops the reference it acquires
before returning.  The patch also adjusts all the callers of
driver_find() to remove the now unnecessary calls to put_driver().

In addition, the patch adds a warning to driver_find(): Callers must
make sure the driver they are searching for does not get unloaded
while they are using it.  This has always been the case; driver_find()
has never prevented a driver from being unregistered or unloaded.
Hence the patch will not introduce any new bugs.  The existing callers
all seem to be okay in this respect, however I don't understand the
video drivers well enough to be certain about them.

Signed-off-by: default avatarAlan Stern <stern@rowland.harvard.edu>
CC: Dmitry Torokhov <dmitry.torokhov@gmail.com>
CC: Kyungmin Park <kyungmin.park@samsung.com>
CC: Andy Walls <awalls@md.metrocast.net>
CC: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 2b31594a

drivers/base/driver.c

+5 −2
Original line number Diff line number Diff line
@@ -234,7 +234,6 @@ int driver_register(struct device_driver *drv) 


	other = driver_find(drv->name, drv->bus);

	if (other) {

		put_driver(other);

		printk(KERN_ERR "Error: Driver '%s' is already registered, "

			"aborting...\n", drv->name);

		return -EBUSY;
@@ -275,7 +274,9 @@ EXPORT_SYMBOL_GPL(driver_unregister); 
 * Call kset_find_obj() to iterate over list of drivers on

 * a bus to find driver by name. Return driver if found.

 *

 * Note that kset_find_obj increments driver's reference count.

 * This routine provides no locking to prevent the driver it returns

 * from being unregistered or unloaded while the caller is using it.

 * The caller is responsible for preventing this.

 */

struct device_driver *driver_find(const char *name, struct bus_type *bus)

{
@@ -283,6 +284,8 @@ struct device_driver *driver_find(const char *name, struct bus_type *bus) 
	struct driver_private *priv;



	if (k) {

		/* Drop reference added by kset_find_obj() */

		kobject_put(k);

		priv = to_driver(k);

		return priv->driver;

	}

drivers/input/gameport/gameport.c

+0 −1
Original line number Diff line number Diff line
@@ -449,7 +449,6 @@ static ssize_t gameport_rebind_driver(struct device *dev, struct device_attribut 
	} else if ((drv = driver_find(buf, &gameport_bus)) != NULL) {

		gameport_disconnect_port(gameport);

		error = gameport_bind_driver(gameport, to_gameport_driver(drv));

		put_driver(drv);

	} else {

		error = -EINVAL;

	}

drivers/input/serio/serio.c

+0 −1
Original line number Diff line number Diff line
@@ -441,7 +441,6 @@ static ssize_t serio_rebind_driver(struct device *dev, struct device_attribute * 
	} else if ((drv = driver_find(buf, &serio_bus)) != NULL) {

		serio_disconnect_port(serio);

		error = serio_bind_driver(serio, to_serio_driver(drv));

		put_driver(drv);

		serio_remove_duplicate_events(serio, SERIO_RESCAN_PORT);

	} else {

		error = -EINVAL;

drivers/media/video/cx18/cx18-alsa-main.c

+0 −1
Original line number Diff line number Diff line
@@ -285,7 +285,6 @@ static void __exit cx18_alsa_exit(void) 


	drv = driver_find("cx18", &pci_bus_type);

	ret = driver_for_each_device(drv, NULL, NULL, cx18_alsa_exit_callback);

	put_driver(drv);



	cx18_ext_init = NULL;

	printk(KERN_INFO "cx18-alsa: module unload complete\n");

drivers/media/video/ivtv/ivtvfb.c

+0 −2
Original line number Diff line number Diff line
@@ -1293,7 +1293,6 @@ static int __init ivtvfb_init(void) 


	drv = driver_find("ivtv", &pci_bus_type);

	err = driver_for_each_device(drv, NULL, &registered, ivtvfb_callback_init);

	put_driver(drv);

	if (!registered) {

		printk(KERN_ERR "ivtvfb:  no cards found\n");

		return -ENODEV;
@@ -1310,7 +1309,6 @@ static void ivtvfb_cleanup(void) 


	drv = driver_find("ivtv", &pci_bus_type);

	err = driver_for_each_device(drv, NULL, NULL, ivtvfb_callback_cleanup);

	put_driver(drv);

}



module_init(ivtvfb_init);

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