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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 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 EFB36CA9EC6 for ; Wed, 30 Oct 2019 19:43:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C66FF2080F for ; Wed, 30 Oct 2019 19:43:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572464615; bh=SvrbAEw49Plnafe/VzNSWq8FLiN2PZsNxZj5PIYPCAQ=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=ZzzK7c91Dza3xVebYgoUaYsAZsj7u4+yQZFGGkcMhB1gFOuX9C09pXguaPpzZRO5J E6siihZlgqBRZJnGb08gfu7UoJuHq6xlJrBVVlrTW4VzOXbxl1zFvxSXuQvw6itMpM vW6QiCF2RS9dR1npPe7v62oycV+bB5ibvd3hbJ1U= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726501AbfJ3Tne (ORCPT ); Wed, 30 Oct 2019 15:43:34 -0400 Received: from mail.kernel.org ([198.145.29.99]:35244 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726261AbfJ3Tne (ORCPT ); Wed, 30 Oct 2019 15:43:34 -0400 Received: from archlinux (cpc149474-cmbg20-2-0-cust94.5-4.cable.virginm.net [82.4.196.95]) (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 E6997205C9; Wed, 30 Oct 2019 19:43:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572464613; bh=SvrbAEw49Plnafe/VzNSWq8FLiN2PZsNxZj5PIYPCAQ=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=qhMfLygR9U7KoGtM2N9i/dXW6g1ijNGhj7Oz//aFnrSyQHID47A0Xju37huThLgpU h2ojTqe8N+JdKsUkmDhwMG6UVR57UeaIW3J+7nW8m+arNodehDgUpxDiZMAUYkY6hF qhqdix6PJKUna/ZSbL6CNrR4Cu4Vn9z04ds/n3uw= Date: Wed, 30 Oct 2019 19:43:25 +0000 From: Jonathan Cameron To: Bart Van Assche Cc: Peter Zijlstra , Ingo Molnar , Thomas Gleixner , Christoph Hellwig , "Martin K . Petersen" , linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org, Hartmut Knaack , Lars-Peter Clausen , Peter Meerwald-Stadler , linux-iio@vger.kernel.org Subject: Re: [PATCH 4/9] drivers/iio: Sign extend without triggering implementation-defined behavior Message-ID: <20191030194325.2ad20a8e@archlinux> In-Reply-To: <20191028200700.213753-5-bvanassche@acm.org> References: <20191028200700.213753-1-bvanassche@acm.org> <20191028200700.213753-5-bvanassche@acm.org> X-Mailer: Claws Mail 3.17.4 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 28 Oct 2019 13:06:55 -0700 Bart Van Assche wrote: > From the C standard: "The result of E1 >> E2 is E1 right-shifted E2 bit > positions. If E1 has an unsigned type or if E1 has a signed type and a > nonnegative value, the value of the result is the integral part of the > quotient of E1 / 2E2 . If E1 has a signed type and a negative value, the > resulting value is implementation-defined." > > Hence use sign_extend_24_to_32() instead of "<< 8 >> 8". +CC linux-iio > > Cc: Jonathan Cameron > Cc: Hartmut Knaack > Cc: Lars-Peter Clausen > Cc: Peter Meerwald-Stadler > Signed-off-by: Bart Van Assche > --- > drivers/iio/common/st_sensors/st_sensors_core.c | 7 +------ > 1 file changed, 1 insertion(+), 6 deletions(-) > > diff --git a/drivers/iio/common/st_sensors/st_sensors_core.c b/drivers/iio/common/st_sensors/st_sensors_core.c > index 4a3064fb6cd9..94a9cec69cd7 100644 > --- a/drivers/iio/common/st_sensors/st_sensors_core.c > +++ b/drivers/iio/common/st_sensors/st_sensors_core.c > @@ -21,11 +21,6 @@ > > #include "st_sensors_core.h" > > -static inline u32 st_sensors_get_unaligned_le24(const u8 *p) > -{ > - return (s32)((p[0] | p[1] << 8 | p[2] << 16) << 8) >> 8; > -} > - > int st_sensors_write_data_with_mask(struct iio_dev *indio_dev, > u8 reg_addr, u8 mask, u8 data) > { > @@ -556,7 +551,7 @@ static int st_sensors_read_axis_data(struct iio_dev *indio_dev, > else if (byte_for_channel == 2) > *data = (s16)get_unaligned_le16(outdata); > else if (byte_for_channel == 3) > - *data = (s32)st_sensors_get_unaligned_le24(outdata); > + *data = get_unaligned_signed_le24(outdata); > > st_sensors_free_memory: > kfree(outdata);