From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AAEECC38A2A for ; Thu, 7 May 2020 11:15:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8C3D12495A for ; Thu, 7 May 2020 11:15:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588850130; bh=m5j26vopqsarHASCUs41VneRgz6W4ivAN8SWIs8XUAo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=f09nXYjaSJi8PHLTTHnNXESrZyo1ewKDWlcXfm3igxNan/KGr3LJewgYX/JDUL6AS 8bUXE8WzA29r9+dm8ROCnnprSm0zTb5fu5BEJINZkVkkFQjNrhwVtLjL612N98FsG7 thytS8zJBpOa6Bv7GhyaMuAN0iScNoHcwMgGba2A= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726942AbgEGLPa (ORCPT ); Thu, 7 May 2020 07:15:30 -0400 Received: from mail.kernel.org ([198.145.29.99]:45922 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725903AbgEGLP3 (ORCPT ); Thu, 7 May 2020 07:15:29 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 839FD20870; Thu, 7 May 2020 11:15:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588850129; bh=m5j26vopqsarHASCUs41VneRgz6W4ivAN8SWIs8XUAo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=io0+5PU2Jeftf20wluUzmyi6annaxFgvMBpalV5HD+3n1J20l9FbtshQAzuO3We6G WoUGLmhyX19mn3i2NhD5tGOlVldDjiTX0Iy1pXVWMgvHqvvYFc+I35BG5JPIcCsOYj XIS5ok98Sh/Aiopp4KLuMTh3HNg0bPK7aW4zOP5M= Date: Thu, 7 May 2020 13:15:26 +0200 From: Greg KH To: Jia-Ju Bai Cc: mchehab@kernel.org, allison@lohutok.net, tglx@linutronix.de, rfontana@redhat.com, tomasbortoli@gmail.com, sean@mess.org, linux-media@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] media: usb: ttusb-dec: reduce the number of memory reads in ttusb_dec_handle_irq() Message-ID: <20200507111526.GA1498671@kroah.com> References: <20200507102521.17602-1-baijiaju1990@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200507102521.17602-1-baijiaju1990@gmail.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 07, 2020 at 06:25:21PM +0800, Jia-Ju Bai wrote: > In ttusb_dec_handle_irq(), buffer[4] is continuously read from memory > three times, without being modified. > To reduce the number of memory reads, buffer[4] is first assigned to a > local variable index, and then index is used to replace buffer[4]. > > Signed-off-by: Jia-Ju Bai > --- > drivers/media/usb/ttusb-dec/ttusb_dec.c | 9 +++++---- > 1 file changed, 5 insertions(+), 4 deletions(-) > > diff --git a/drivers/media/usb/ttusb-dec/ttusb_dec.c b/drivers/media/usb/ttusb-dec/ttusb_dec.c > index 3198f9624b7c..8543c552515b 100644 > --- a/drivers/media/usb/ttusb-dec/ttusb_dec.c > +++ b/drivers/media/usb/ttusb-dec/ttusb_dec.c > @@ -250,6 +250,7 @@ static void ttusb_dec_handle_irq( struct urb *urb) > struct ttusb_dec *dec = urb->context; > char *buffer = dec->irq_buffer; > int retval; > + int index = buffer[4]; > > switch(urb->status) { > case 0: /*success*/ > @@ -281,11 +282,11 @@ static void ttusb_dec_handle_irq( struct urb *urb) > * this should/could be added later ... > * for now lets report each signal as a key down and up > */ > - if (buffer[4] - 1 < ARRAY_SIZE(rc_keys)) { > - dprintk("%s:rc signal:%d\n", __func__, buffer[4]); > - input_report_key(dec->rc_input_dev, rc_keys[buffer[4] - 1], 1); > + if (index - 1 < ARRAY_SIZE(rc_keys)) { > + dprintk("%s:rc signal:%d\n", __func__, index); > + input_report_key(dec->rc_input_dev, rc_keys[index - 1], 1); > input_sync(dec->rc_input_dev); > - input_report_key(dec->rc_input_dev, rc_keys[buffer[4] - 1], 0); > + input_report_key(dec->rc_input_dev, rc_keys[index - 1], 0); > input_sync(dec->rc_input_dev); > } > } > -- > 2.17.1 > Reviewed-by: Greg Kroah-Hartman