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driver core: bus: add bus_get_dev_root() function

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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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Greg Kroah-Hartman 2023-02-09 10:35:56 +01:00
parent ad8685d0f6
commit 8c99377e61
4 changed files with 39 additions and 6 deletions
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20
drivers/base/bus.c
View File

@ -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);

14
drivers/base/core.c
View File

@ -3173,8 +3173,9 @@ static DEFINE_MUTEX(gdp_mutex);
static struct kobject *get_device_parent(struct device *dev,
struct device *parent)
{
struct kobject *kobj = NULL;
if (dev->class) {
struct kobject *kobj = NULL;
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;

10
drivers/base/cpu.c
View File

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

1
include/linux/device/bus.h
View File

@ -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