From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753368AbbKXMd5 (ORCPT ); Tue, 24 Nov 2015 07:33:57 -0500 Received: from mail-lf0-f49.google.com ([209.85.215.49]:32826 "EHLO mail-lf0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752960AbbKXMdz (ORCPT ); Tue, 24 Nov 2015 07:33:55 -0500 From: Rasmus Villemoes To: Jiri Kosina Cc: Rasmus Villemoes , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] HID: debug: improve hid_debug_event() Date: Tue, 24 Nov 2015 13:33:47 +0100 Message-Id: <1448368427-1669-1-git-send-email-linux@rasmusvillemoes.dk> X-Mailer: git-send-email 2.6.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The code in hid_debug_event() causes horrible code generation. First, we do a strlen() call for every byte we copy (we're doing a store to global memory, so gcc has no way of proving that strlen(buf) doesn't change). Second, since both i, list->tail and HID_DEBUG_BUFSIZE have signed type, the modulo computation has to take into account the possibility that list->tail+i is negative, so it's not just a simple and. Fix the former by simply not doing strlen() at all (we have to load buf[i] anyway, so testing it is almost free) and the latter by changing i to unsigned. This cuts 29% (69 bytes) of the size of the function. Signed-off-by: Rasmus Villemoes --- drivers/hid/hid-debug.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/hid/hid-debug.c b/drivers/hid/hid-debug.c index 2886b645ced7..acfb522a432a 100644 --- a/drivers/hid/hid-debug.c +++ b/drivers/hid/hid-debug.c @@ -659,13 +659,13 @@ EXPORT_SYMBOL_GPL(hid_dump_device); /* enqueue string to 'events' ring buffer */ void hid_debug_event(struct hid_device *hdev, char *buf) { - int i; + unsigned i; struct hid_debug_list *list; unsigned long flags; spin_lock_irqsave(&hdev->debug_list_lock, flags); list_for_each_entry(list, &hdev->debug_list, node) { - for (i = 0; i < strlen(buf); i++) + for (i = 0; buf[i]; i++) list->hid_debug_buf[(list->tail + i) % HID_DEBUG_BUFSIZE] = buf[i]; list->tail = (list->tail + i) % HID_DEBUG_BUFSIZE; -- 2.6.1