From patchwork Thu May 7 10:25:21 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jia-Ju Bai X-Patchwork-Id: 11533013 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 9D724139A for ; Thu, 7 May 2020 10:25:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 82EE6208E4 for ; Thu, 7 May 2020 10:25:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="TtSTJiYO" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726625AbgEGKZt (ORCPT ); Thu, 7 May 2020 06:25:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39114 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1725910AbgEGKZt (ORCPT ); Thu, 7 May 2020 06:25:49 -0400 Received: from mail-pl1-x642.google.com (mail-pl1-x642.google.com [IPv6:2607:f8b0:4864:20::642]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2C32FC061A10; Thu, 7 May 2020 03:25:49 -0700 (PDT) Received: by mail-pl1-x642.google.com with SMTP id z6so1890840plk.10; Thu, 07 May 2020 03:25:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id; bh=eyQI8JLiukg5hsarHG9sBQAMSiRoxhwvfjPhjSw8K/o=; b=TtSTJiYO+U3hIwC0bLXhTg2Vy+Ka8M7YD6iWszwVE+AypowHMOiGM8fYUTj2omh78v T00iT/zY5mum9tpyN01TwjDP9hTqtaELLjZjB+MCwni1fFovJ2nyavfE6yKzSBOXtzHM cSNhSMCnKWK2IPrkNmwQl8L/hJ13W9v7+QV5g53lD2ogs6JcNLDRR2a5IwvQW6mrzPey fi69zYGUMeMpW+0gixXZTZ/PX3goIajW+QO6Nw7Lg6qdeeHez8LXbvKi+YnWYjy9vlNF 71eTkl7qIgZOO3v8VLyJaOQbzusevYANrhUngDBHumQVqsQuJZ/xvuU2fPAM/QClCJRM WBeQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=eyQI8JLiukg5hsarHG9sBQAMSiRoxhwvfjPhjSw8K/o=; b=RCkgH5IJnP1mlf3AhXWfugw4DJyMuoHrvJaadu9UpHA7G8z9fStMRZR8zdNmY9AXtJ WvRa06kmoHE0CqrI1WEHthPDK5ZpGhjhERnp9E2XaUFM0hxTPpfCDT5kjvD2GYDld1yK j0DtUVAB0rKa0jfDeho8udWPyVA9FnuLuX1QryD1vmewXNymRWD+SteRKFBx5xgwcp9B BR/44+3/cQ8FYvByno3MSPSR+8S5pFGqQjG6OIbaHuGOLYhrIjob0nPjNvyUfKGISO8i xZ/XPVRNtvAzpuqEXLCQTuiUnejLuEjO0jLm/Nm2AbQzdzwN84Vmybi5EZBBtoDkQ1pk 6XKg== X-Gm-Message-State: AGi0PuZdMNBDTREp12NF1Sd2J3c2TTM/crX7lmMEdquAIw1vXP9Rj23r jlJYblWTDt98Q2of6x6oeww= X-Google-Smtp-Source: APiQypKtLMObouxK278qs8imSqkHllBxKT/Bz7CMJw4dBFbW2tzbNDXxr+1epqKk5H4jnl9GFfbnQw== X-Received: by 2002:a17:902:bf46:: with SMTP id u6mr12150109pls.318.1588847148711; Thu, 07 May 2020 03:25:48 -0700 (PDT) Received: from localhost.localdomain ([120.244.109.48]) by smtp.gmail.com with ESMTPSA id w75sm4432029pfc.156.2020.05.07.03.25.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 07 May 2020 03:25:48 -0700 (PDT) From: Jia-Ju Bai To: mchehab@kernel.org, gregkh@linuxfoundation.org, allison@lohutok.net, tglx@linutronix.de, rfontana@redhat.com, tomasbortoli@gmail.com, sean@mess.org Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, Jia-Ju Bai Subject: [PATCH] media: usb: ttusb-dec: reduce the number of memory reads in ttusb_dec_handle_irq() Date: Thu, 7 May 2020 18:25:21 +0800 Message-Id: <20200507102521.17602-1-baijiaju1990@gmail.com> X-Mailer: git-send-email 2.17.1 Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org 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 Reviewed-by: Greg Kroah-Hartman --- 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); } }