Commit 8c99377e authored by Greg Kroah-Hartman's avatar Greg Kroah-Hartman
Browse files

driver core: bus: add bus_get_dev_root() function 

Instead of poking around in the struct bus_type directly for the
dev_root pointer, provide a function to return it properly reference
counted, if it is present in the bus.  This will be needed to move the
pointer out of struct bus_type in the future.

Use the function in the driver core code at the same time it is
introduced to verify that it works properly.

Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Link: https://lore.kernel.org/r/20230209093556.19132-1-gregkh@linuxfoundation.org


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent ad8685d0

drivers/base/bus.c

+20 −0
Original line number Diff line number Diff line
@@ -1334,6 +1334,26 @@ bool bus_is_registered(const struct bus_type *bus) 
	return is_initialized;

}



/**

 * bus_get_dev_root - return a pointer to the "device root" of a bus

 * @bus: bus to return the device root of.

 *

 * If a bus has a "device root" structure, return it, WITH THE REFERENCE

 * COUNT INCREMENTED.

 *

 * Note, when finished with the device, a call to put_device() is required.

 *

 * If the device root is not present (or bus is not a valid pointer), NULL

 * will be returned.

 */

struct device *bus_get_dev_root(const struct bus_type *bus)

{

	if (bus)

		return get_device(bus->dev_root);

	return NULL;

}

EXPORT_SYMBOL_GPL(bus_get_dev_root);



int __init buses_init(void)

{

	bus_kset = kset_create_and_add("bus", &bus_uevent_ops, NULL);

drivers/base/core.c

+11 −3
Original line number Diff line number Diff line
@@ -3173,8 +3173,9 @@ static DEFINE_MUTEX(gdp_mutex); 
static struct kobject *get_device_parent(struct device *dev,

					 struct device *parent)

{

	if (dev->class) {

	struct kobject *kobj = NULL;



	if (dev->class) {

		struct kobject *parent_kobj;

		struct kobject *k;
@@ -3222,8 +3223,15 @@ static struct kobject *get_device_parent(struct device *dev, 
	}



	/* subsystems can specify a default root directory for their devices */

	if (!parent && dev->bus && dev->bus->dev_root)

		return &dev->bus->dev_root->kobj;

	if (!parent && dev->bus) {

		struct device *dev_root = bus_get_dev_root(dev->bus);



		if (dev_root) {

			kobj = &dev_root->kobj;

			put_device(dev_root);

			return kobj;

		}

	}



	if (parent)

		return &parent->kobj;

drivers/base/cpu.c

+7 −3
Original line number Diff line number Diff line
@@ -610,9 +610,13 @@ static const struct attribute_group cpu_root_vulnerabilities_group = { 


static void __init cpu_register_vulnerabilities(void)

{

	if (sysfs_create_group(&cpu_subsys.dev_root->kobj,

			       &cpu_root_vulnerabilities_group))

	struct device *dev = bus_get_dev_root(&cpu_subsys);



	if (dev) {

		if (sysfs_create_group(&dev->kobj, &cpu_root_vulnerabilities_group))

			pr_err("Unable to register CPU vulnerabilities\n");

		put_device(dev);

	}

}



#else

include/linux/device/bus.h

+1 −0
Original line number Diff line number Diff line
@@ -282,5 +282,6 @@ enum bus_notifier_event { 
};



extern struct kset *bus_get_kset(const struct bus_type *bus);

struct device *bus_get_dev_root(const struct bus_type *bus);



#endif