From patchwork Thu Jun 27 07:20:45 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Bastien Nocera X-Patchwork-Id: 11019001 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id E7924112C for ; Thu, 27 Jun 2019 07:20:54 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id C55381FF81 for ; Thu, 27 Jun 2019 07:20:54 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id B9BD128857; Thu, 27 Jun 2019 07:20:54 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A9FA328821 for ; Thu, 27 Jun 2019 07:20:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726059AbfF0HUx (ORCPT ); Thu, 27 Jun 2019 03:20:53 -0400 Received: from relay12.mail.gandi.net ([217.70.178.232]:51407 "EHLO relay12.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726054AbfF0HUx (ORCPT ); Thu, 27 Jun 2019 03:20:53 -0400 Received: from classic (mon69-7-83-155-44-161.fbx.proxad.net [83.155.44.161]) (Authenticated sender: hadess@hadess.net) by relay12.mail.gandi.net (Postfix) with ESMTPSA id E8E6D200007; Thu, 27 Jun 2019 07:20:46 +0000 (UTC) Message-ID: <8b5ad111c555eb548c4f3da6d55e426a15ebf59b.camel@hadess.net> Subject: [PATCH v2] iio: iio-utils: Fix possible incorrect mask calculation From: Bastien Nocera To: linux-iio@vger.kernel.org Cc: Jonathan Cameron Date: Thu, 27 Jun 2019 09:20:45 +0200 User-Agent: Evolution 3.32.2 (3.32.2-1.fc30) MIME-Version: 1.0 Sender: linux-iio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On some machines, iio-sensor-proxy was returning all 0's for IIO sensor values. It turns out that the bits_used for this sensor is 32, which makes the mask calculation: *mask = (1 << 32) - 1; If the compiler interprets the 1 literals as 32-bit ints, it generates undefined behavior depending on compiler version and optimization level. On my system, it optimizes out the shift, so the mask value becomes *mask = (1) - 1; With a mask value of 0, iio-sensor-proxy will always return 0 for every axis. Avoid incorrect 0 values caused by compiler optimization. See original fix by Brett Dutro in iio-sensor-proxy: https://github.com/hadess/iio-sensor-proxy/commit/9615ceac7c134d838660e209726cd86aa2064fd3 Signed-off-by: Bastien Nocera --- tools/iio/iio_utils.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/tools/iio/iio_utils.c b/tools/iio/iio_utils.c index a22b6e8fad46..7399eb7f1378 100644 --- a/tools/iio/iio_utils.c +++ b/tools/iio/iio_utils.c @@ -156,9 +156,9 @@ int iioutils_get_type(unsigned *is_signed, unsigned *bytes, unsigned *bits_used, *be = (endianchar == 'b'); *bytes = padint / 8; if (*bits_used == 64) - *mask = ~0; + *mask = ~(0ULL); else - *mask = (1ULL << *bits_used) - 1; + *mask = (1ULL << *bits_used) - 1ULL; *is_signed = (signchar == 's'); if (fclose(sysfsfp)) {