ACPI: Rework acpi_get_child() to be more efficient

Observe that acpi_get_child() doesn't need to use the helper
struct acpi_find_child structure and change it to work without it.
Also, using acpi_get_object_info() to get the output of _ADR for the
given device is overkill, because that function does much more than
just evaluating _ADR (let alone the additional memory allocation
done by it).

Moreover, acpi_get_child() doesn't need to loop any more once it has
found a matching handle, so make it stop in that case.  To prevent
the results from changing, make it use do_acpi_find_child() as
a post-order callback.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 13 insertions, 22 deletions

diff --git a/drivers/acpi/glue.c b/drivers/acpi/glue.c
index 35da18113216..e9e486f79b35 100644
--- a/drivers/acpi/glue.c
+++ b/drivers/acpi/glue.c
@@ -95,40 +95,31 @@ static int acpi_find_bridge_device(struct device *dev, acpi_handle * handle)
         return ret;
 }
 
-/* Get device's handler per its address under its parent */
-struct acpi_find_child {
-        acpi_handle handle;
-        u64 address;
-};
-
-static acpi_status
-do_acpi_find_child(acpi_handle handle, u32 lvl, void *context, void **rv)
+static acpi_status do_acpi_find_child(acpi_handle handle, u32 lvl_not_used,
+                                      void *addr_p, void **ret_p)
 {
+        unsigned long long addr;
         acpi_status status;
-        struct acpi_device_info *info;
-        struct acpi_find_child *find = context;
-
-        status = acpi_get_object_info(handle, &info);
-        if (ACPI_SUCCESS(status)) {
-                if ((info->address == find->address)
-                        && (info->valid & ACPI_VALID_ADR))
-                        find->handle = handle;
-                kfree(info);
+
+        status = acpi_evaluate_integer(handle, METHOD_NAME__ADR, NULL, &addr);
+        if (ACPI_SUCCESS(status) && addr == *((u64 *)addr_p)) {
+                *ret_p = handle;
+                return AE_CTRL_TERMINATE;
         }
         return AE_OK;
 }
 
 acpi_handle acpi_get_child(acpi_handle parent, u64 address)
 {
-        struct acpi_find_child find = { NULL, address };
+        void *ret = NULL;
 
         if (!parent)
                 return NULL;
-        acpi_walk_namespace(ACPI_TYPE_DEVICE, parent,
-                            1, do_acpi_find_child, NULL, &find, NULL);
-        return find.handle;
-}
 
+        acpi_walk_namespace(ACPI_TYPE_DEVICE, parent, 1, NULL,
+                            do_acpi_find_child, &address, &ret);
+        return (acpi_handle)ret;
+}
 EXPORT_SYMBOL(acpi_get_child);
 
 static int acpi_bind_one(struct device *dev, acpi_handle handle)