ACPI: some issues managing the linked list in acpi_pci_register/unregister_driver

I submitted an earlier patch on this to lkml with just a single line initializing the sub_driver variable to NULL. This was insufficient. This patch fixes some link list management issues in adding a new acpi_pci_driver type to the sub_driver list. This is against 2.6.30

@@ -76,7 +76,7 @@ struct acpi_pci_root {
 

static LIST_HEAD(acpi_pci_roots);

-static struct acpi_pci_driver *sub_driver; +static struct acpi_pci_driver *sub_driver = NULL; static DEFINE_MUTEX(osc_lock);

int acpi_pci_register_driver(struct acpi_pci_driver *driver) @@ -84,10 +84,9 @@ int acpi_pci_register_driver(struct acpi

       int n = 0;
       struct list_head *entry;

- struct acpi_pci_driver **pptr = &sub_driver;
- while (*pptr)
- pptr = &(*pptr)->next;
- *pptr = driver;

+        /* Add to the head of the list */
+        driver->next = sub_driver;
+        sub_driver = driver;

       if (!driver->add)
               return 0;
@@ -107,15 +106,21 @@ EXPORT_SYMBOL(acpi_pci_register_driver);
void acpi_pci_unregister_driver(struct acpi_pci_driver *driver)
{
       struct list_head *entry;

+ struct acpi_pci_driver *pptr, *prev;

- struct acpi_pci_driver **pptr = &sub_driver;
- while (*pptr) {
- if (*pptr == driver)
+ /* Remove driver from the sub_driver list */
+ for (prev = NULL, pptr = sub_driver; pptr;
+ prev = pptr, pptr=pptr->next)
+ {
+ if (pptr == driver) {
+ if (!prev)
+ sub_driver = driver->next;
+ else

+                               prev->next = pptr->next;
                       break;
-               pptr = &(*pptr)->next;
+               }
       }
-       BUG_ON(!*pptr);
-       *pptr = (*pptr)->next;
+       BUG_ON(!pptr);

       if (!driver->remove)
               return;

--