linux-kernel - [PATCH] ACPI: Rework acpi_get

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Date:	Wed, 19 Dec 2012 12:27:18 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	ACPI Devel Maling List <linux-acpi@...r.kernel.org>
Cc:	LKML <linux-kernel@...r.kernel.org>, Len Brown <lenb@...nel.org>
Subject: [PATCH] ACPI: Rework acpi_get_child() to be more efficient

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Observe that acpi_get_child() doesn't need to use the helper
struct acpi_find_child structure and change it to work without 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@...el.com>
---
 drivers/acpi/glue.c |   36 ++++++++++++++++--------------------
 1 file changed, 16 insertions(+), 20 deletions(-)

Index: linux/drivers/acpi/glue.c
===================================================================
--- linux.orig/drivers/acpi/glue.c
+++ linux/drivers/acpi/glue.c
@@ -90,38 +90,34 @@ static int acpi_find_bridge_device(struc
 	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)
 {
-	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);
+	if (ACPI_SUCCESS(acpi_get_object_info(handle, &info))) {
+		bool found = info->address == *((u64 *)addr_p)
+				&& (info->valid & ACPI_VALID_ADR);
+
+		ACPI_FREE(info);
+		if (found) {
+			*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);

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