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=-24.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 9F4F3C2B9F4 for ; Fri, 25 Jun 2021 17:57:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 809DD6195B for ; Fri, 25 Jun 2021 17:57:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230021AbhFYSAL (ORCPT ); Fri, 25 Jun 2021 14:00:11 -0400 Received: from mail.kernel.org ([198.145.29.99]:46006 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229531AbhFYSAK (ORCPT ); Fri, 25 Jun 2021 14:00:10 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id C697461962; Fri, 25 Jun 2021 17:57:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1624643869; bh=oOSj0X4FE7FErjVHq3yjylZUVNnZQxO6Kpg8jzl59ig=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mhMtgKGfZyF1K3+8aZ/Qhxu42oLBbajrDychBw8zh9rQtIpvD2XTRCV/TC4b9xiK3 hjFFPa4ufe9/OZn1fppoff2VH7udIPTibbPY8azMQJNb+naWQ6Fe83mOE+gYxgq1um 6AfgBHA001YuNyhmTpja8MQxnEWXLQuGfxvyeC6nh4VzRxO5FbLPmLxuf4hcXq48O6 5lQQ7d5PeWqQuwgMkKaPoQlsp8je9R0AODopWXSfvX6a0iD5D2yZmGbAftaxYEixDh mJqm04VHek6yv4lG8h+l39yoT7XsXD3myjiOgM95dNsNvViPxCcDX7/1IiC3hOarJ0 3rSp6Gd+yuq3A== From: Nathan Chancellor To: "Geoffrey D. Bennett" , Jaroslav Kysela , Takashi Iwai Cc: Nick Desaulniers , alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com, Nathan Chancellor Subject: [PATCH v2] ALSA: usb-audio: scarlett2: Fix for loop increment in scarlett2_usb_get_config Date: Fri, 25 Jun 2021 10:54:19 -0700 Message-Id: <20210625175418.2019892-1-nathan@kernel.org> X-Mailer: git-send-email 2.32.0.93.g670b81a890 In-Reply-To: References: MIME-Version: 1.0 X-Patchwork-Bot: notify Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Clang warns: sound/usb/mixer_scarlett_gen2.c:1189:32: warning: expression result unused [-Wunused-value] for (i = 0; i < count; i++, (u16 *)buf++) ^ ~~~~~ 1 warning generated. It appears the intention was to cast the void pointer to a u16 pointer so that the data could be iterated through like an array of u16 values. However, the cast happens after the increment because a cast is an rvalue, whereas the post-increment operator only works on lvalues, so the loop does not iterate as expected. This is not a bug in practice because count is not greater than one at the moment but this could change in the future so this should be fixed. Replace the cast with a temporary variable of the proper type, which is less error prone and fixes the iteration. Do the same thing for the 'u8 *' below this if block. Fixes: ac34df733d2d ("ALSA: usb-audio: scarlett2: Update get_config to do endian conversion") Link: https://github.com/ClangBuiltLinux/linux/issues/1408 Signed-off-by: Nathan Chancellor --- v1 -> v2: * Use temporary variables of proper type rather than casting, as requested by Takashi. I did not include Geoffrey's ack for this reason. * Mention that there is not a bug at the moment per Geoffrey's comment. sound/usb/mixer_scarlett_gen2.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/sound/usb/mixer_scarlett_gen2.c b/sound/usb/mixer_scarlett_gen2.c index fcba682cd422..b13903bed330 100644 --- a/sound/usb/mixer_scarlett_gen2.c +++ b/sound/usb/mixer_scarlett_gen2.c @@ -1177,17 +1177,22 @@ static int scarlett2_usb_get_config( const struct scarlett2_config *config_item = &scarlett2_config_items[info->has_mixer][config_item_num]; int size, err, i; + u8 *buf_8; u8 value; /* For byte-sized parameters, retrieve directly into buf */ if (config_item->size >= 8) { + u16 *buf_16; + size = config_item->size / 8 * count; err = scarlett2_usb_get(mixer, config_item->offset, buf, size); if (err < 0) return err; - if (size == 2) - for (i = 0; i < count; i++, (u16 *)buf++) - *(u16 *)buf = le16_to_cpu(*(__le16 *)buf); + if (size == 2) { + buf_16 = buf; + for (i = 0; i < count; i++, buf_16++) + *buf_16 = le16_to_cpu(*(__le16 *)buf_16); + } return 0; } @@ -1197,8 +1202,9 @@ static int scarlett2_usb_get_config( return err; /* then unpack from value into buf[] */ + buf_8 = buf; for (i = 0; i < 8 && i < count; i++, value >>= 1) - *(u8 *)buf++ = value & 1; + *buf_8++ = value & 1; return 0; } base-commit: 0cbbeaf370221fc469c95945dd3c1198865c5fe4 -- 2.32.0.93.g670b81a890