ACPI: use memory_read_from_buffer()

Signed-off-by: NAkinobu Mita <akinobu.mita@gmail.com>
Acked-by: NZhang Rui <rui.zhang@intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLen Brown <len.brown@intel.com>

drivers/acpi/system.c

@@ -77,7 +77,6 @@ static ssize_t acpi_table_show(struct kobject *kobj,
 	    container_of(bin_attr, struct acpi_table_attr, attr);
 	struct acpi_table_header *table_header = NULL;
 	acpi_status status;
-	ssize_t ret_count = count;
 
 	status =
 	    acpi_get_table(table_attr->name, table_attr->instance,
@@ -85,18 +84,8 @@ static ssize_t acpi_table_show(struct kobject *kobj,
 	if (ACPI_FAILURE(status))
 		return -ENODEV;
 
-	if (offset >= table_header->length) {
-		ret_count = 0;
-		goto end;
-	}
-
-	if (offset + ret_count > table_header->length)
-		ret_count = table_header->length - offset;
-
-	memcpy(buf, ((char *)table_header) + offset, ret_count);
-
-      end:
-	return ret_count;
+	return memory_read_from_buffer(buf, count, &offset,
+					table_header, table_header->length);
 }
 
 static void acpi_table_attr_init(struct acpi_table_attr *table_attr,