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authorGreg Kroah-Hartman <gregkh@linuxfoundation.org>2023-03-25 20:42:33 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2023-03-29 07:55:07 +0200
commit884f8ce42ccec9d0bf11d8bf9f111e5961ca1c82 (patch)
treeb5aa06b6038676d53c88be5efc210a676df9932a /drivers/base
parent75a2d4226b53710380d1017b3f4c88f937ddba78 (diff)
downloadlinux-next-884f8ce42ccec9d0bf11d8bf9f111e5961ca1c82.tar.gz
driver core: class: implement class_get/put without the private pointer.
Much like what was done in commit 273afac615ad ("driver core: bus: implement bus_get/put() without the private pointer"), it is time to move the driver core away from using the internal private pointer in struct class in order to enable it to be always a constant and be placed in read-only memory in the future. First step in doing this is to create a helper function that turns a 'struct class' into 'struct subsys_private' called class_to_subsys(). class_to_subsys() walks the list of registered busses in the system and finds the matching one based on the pointer to the class itself. As this is a short list, and this function is not on any fast path, it should not be noticable. Implement class_get() and class_put() using this new helper function. Cc: "Rafael J. Wysocki" <rafael@kernel.org> Link: https://lore.kernel.org/r/20230325194234.46588-1-gregkh@linuxfoundation.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/base')
-rw-r--r--drivers/base/class.c81
1 files changed, 63 insertions, 18 deletions
diff --git a/drivers/base/class.c b/drivers/base/class.c
index 04de20e0dba8..c53d6f98cfc6 100644
--- a/drivers/base/class.c
+++ b/drivers/base/class.c
@@ -20,8 +20,70 @@
#include <linux/mutex.h>
#include "base.h"
+/* /sys/class */
+static struct kset *class_kset;
+
#define to_class_attr(_attr) container_of(_attr, struct class_attribute, attr)
+/**
+ * class_to_subsys - Turn a struct class into a struct subsys_private
+ *
+ * @class: pointer to the struct bus_type to look up
+ *
+ * The driver core internals need to work on the subsys_private structure, not
+ * the external struct class pointer. This function walks the list of
+ * registered classes in the system and finds the matching one and returns the
+ * internal struct subsys_private that relates to that class.
+ *
+ * Note, the reference count of the return value is INCREMENTED if it is not
+ * NULL. A call to subsys_put() must be done when finished with the pointer in
+ * order for it to be properly freed.
+ */
+static struct subsys_private *class_to_subsys(const struct class *class)
+{
+ struct subsys_private *sp = NULL;
+ struct kobject *kobj;
+
+ if (!class || !class_kset)
+ return NULL;
+
+ spin_lock(&class_kset->list_lock);
+
+ if (list_empty(&class_kset->list))
+ goto done;
+
+ list_for_each_entry(kobj, &class_kset->list, entry) {
+ struct kset *kset = container_of(kobj, struct kset, kobj);
+
+ sp = container_of_const(kset, struct subsys_private, subsys);
+ if (sp->class == class)
+ goto done;
+ }
+ sp = NULL;
+done:
+ sp = subsys_get(sp);
+ spin_unlock(&class_kset->list_lock);
+ return sp;
+}
+
+static const struct class *class_get(const struct class *class)
+{
+ struct subsys_private *sp = class_to_subsys(class);
+
+ if (sp)
+ return class;
+ return NULL;
+}
+
+static void class_put(const struct class *class)
+{
+ struct subsys_private *sp = class_to_subsys(class);
+
+ /* two puts are required as the call to bus_to_subsys incremented it again */
+ subsys_put(sp);
+ subsys_put(sp);
+}
+
static ssize_t class_attr_show(struct kobject *kobj, struct attribute *attr,
char *buf)
{
@@ -83,10 +145,6 @@ static const struct kobj_type class_ktype = {
.child_ns_type = class_child_ns_type,
};
-/* Hotplug events for classes go to the class subsys */
-static struct kset *class_kset;
-
-
int class_create_file_ns(const struct class *cls, const struct class_attribute *attr,
const void *ns)
{
@@ -109,19 +167,6 @@ void class_remove_file_ns(const struct class *cls, const struct class_attribute
}
EXPORT_SYMBOL_GPL(class_remove_file_ns);
-static struct class *class_get(struct class *cls)
-{
- if (cls)
- kset_get(&cls->p->subsys);
- return cls;
-}
-
-static void class_put(struct class *cls)
-{
- if (cls)
- kset_put(&cls->p->subsys);
-}
-
static struct device *klist_class_to_dev(struct klist_node *n)
{
struct device_private *p = to_device_private_class(n);
@@ -434,7 +479,7 @@ EXPORT_SYMBOL_GPL(class_find_device);
int class_interface_register(struct class_interface *class_intf)
{
- struct class *parent;
+ const struct class *parent;
struct class_dev_iter iter;
struct device *dev;