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=-24.7 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=unavailable 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 41464C49EA6 for ; Sun, 27 Jun 2021 05:18:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1A86961C43 for ; Sun, 27 Jun 2021 05:18:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229588AbhF0FQY (ORCPT ); Sun, 27 Jun 2021 01:16:24 -0400 Received: from mail.kernel.org ([198.145.29.99]:46494 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229472AbhF0FQX (ORCPT ); Sun, 27 Jun 2021 01:16:23 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id BFF0561C18; Sun, 27 Jun 2021 05:13:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1624770840; bh=8SJ0rdNiF1eGxKYghOID17R/TEXH/bxSrVL61q47o6g=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=tsvX004sWQ1Vml6hsSQVSayCX2z9ZKSHM9fz3et7JdxKmZ1cJiKkh1mflXfbEnQwK muYfgh+F0tu0MSrKS2CGUF0eEU5C5axXUHbxuxCTxxO/pGnNECZosGR9xRLLFJZ3di vSZ/jtVj1fpSB6bFV+QEQpSgNzPxavCaDIML/q3r/DsAcwuZ8+TJ7Fgx6ZiI3BNo+q crO3gJBWo4DIHWmOIXn9Q7Jn5ls5tRkuPDl0057Yj+e/BGjHwqOol+xKrMR4KMVr6T jlxFAT2ZtHN4qgYOOsmQATGDN7HAm6s/TeBfAPvvfidcf6Nd6PA3VFG0UtMC7a4Ndd wwAA23J8lpUYw== 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 v5] ALSA: usb-audio: scarlett2: Fix for loop increment in scarlett2_usb_get_config Date: Sat, 26 Jun 2021 22:12:03 -0700 Message-Id: <20210627051202.1888250-1-nathan@kernel.org> X-Mailer: git-send-email 2.32.0.93.g670b81a890 In-Reply-To: <20210625202604.GB23780@m.b4.vu> References: <20210625202604.GB23780@m.b4.vu> 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 Acked-by: Geoffrey D. Bennett Signed-off-by: Nathan Chancellor --- v1 -> v2: * Use temporary variables of proper type rather than casting, as requested by Takashi. * Mention that there is not a bug at the moment per Geoffrey's comment. v2 -> v3: * Restrict scope of buf_16 more, as requested by Geoffrey. * Add Geoffrey's ack. v3 -> v4: * Fix stray newline added below if (config_item->size >= 8) { leftover from buf_16's declaration. v4 -> v5 (or how many times does it take Nathan to get a patch right): * Re-add note about no bug that was dropped in v3 by accident, as noticed by Geoffrey. My apologies for the multiple revisions. sound/usb/mixer_scarlett_gen2.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/sound/usb/mixer_scarlett_gen2.c b/sound/usb/mixer_scarlett_gen2.c index fcba682cd422..161d832cafef 100644 --- a/sound/usb/mixer_scarlett_gen2.c +++ b/sound/usb/mixer_scarlett_gen2.c @@ -1177,6 +1177,7 @@ 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 */ @@ -1185,9 +1186,12 @@ static int scarlett2_usb_get_config( 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) { + u16 *buf_16 = buf; + + for (i = 0; i < count; i++, buf_16++) + *buf_16 = le16_to_cpu(*(__le16 *)buf_16); + } return 0; } @@ -1197,8 +1201,9 @@ 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