linux-kernel - [Update][PATCH] ACPI: Rework acpi_get

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Date:	Wed, 26 Dec 2012 23:42:49 +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: [Update][PATCH] ACPI: Rework acpi_get_child() to be more efficient

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

The difference from the previous version is the replacement of
acpi_get_object_info() with the direct execution of _ADR, which is
more straightforward.

Thanks,
Rafael

---
 drivers/acpi/glue.c |   33 ++++++++++++---------------------
 1 file changed, 12 insertions(+), 21 deletions(-)

Index: linux/drivers/acpi/glue.c
===================================================================
--- linux.orig/drivers/acpi/glue.c
+++ linux/drivers/acpi/glue.c
@@ -93,40 +93,31 @@ 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)
 {
+	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)

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