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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A9C12E92718 for ; Thu, 5 Oct 2023 15:59:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236259AbjJEP6a (ORCPT ); Thu, 5 Oct 2023 11:58:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37758 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237198AbjJEP5g (ORCPT ); Thu, 5 Oct 2023 11:57:36 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9C9F95FEB; Thu, 5 Oct 2023 08:17:13 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3EB54C433C7; Thu, 5 Oct 2023 15:17:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1696519033; bh=CaTNBuS9Fb+l4tmi5Xy/KGFrITEbvOikbxtS6uzbucQ=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=RmrQmJWsiOI0JOKuWZWH5xdVVFwz84p4aSCWCLx4AbpCab9LDFs+I7CKPX4pWDy71 y8S1ua7EdGnzFqblYc7vfLslKvpbicVKf9a9jx2Gi7UZH1Brwsin7U39NGSrlz2bjg 2CpMIAyxKbfSrs2ySjKKLzB6X7JCNECwTURpmEjjIEt8h/QU+wU5uOjfSGReSFWqMy VSBZ9Ecczyox3r88Si/HGCH96nlwsN2/7kREX5rHFrLqIfEICs2WqnnKXxMHFBcjTA YByJwxMeeQy08EwPtvKSZhIocbYJx1EeCn1a7QrifspH0K1HkhDFgm8dKDOwnz2qhM 4Py4qq+UtZvlg== Date: Thu, 5 Oct 2023 16:17:18 +0100 From: Jonathan Cameron To: Matti Vaittinen Cc: Matti Vaittinen , Lars-Peter Clausen , linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v6] tools: iio: iio_generic_buffer ensure alignment Message-ID: <20231005161718.612fab8c@jic23-huawei> In-Reply-To: References: X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org On Tue, 3 Oct 2023 12:57:47 +0300 Matti Vaittinen wrote: > The iio_generic_buffer can return garbage values when the total size of > scan data is not a multiple of the largest element in the scan. This can be > demonstrated by reading a scan, consisting, for example of one 4-byte and > one 2-byte element, where the 4-byte element is first in the buffer. > > The IIO generic buffer code does not take into account the last two > padding bytes that are needed to ensure that the 4-byte data for next > scan is correctly aligned. > > Add the padding bytes required to align the next sample with the scan size. > > Signed-off-by: Matti Vaittinen > Fixes: e58537ccce73 ("staging: iio: update example application.") Applied to the togreg branch of iio.git and pushed out as testing for all the normal reasons. Thanks, Jonathan > > --- > Revision history > v5 => v6: > - fix typo pointed by Andy (wan't => want). > v4 => v5: > - drop unnecessary comment. > - drop all other patches as those were already applied. > - add Fixes-tag. > v3 => v4: > - drop extra print and TODO coment > - add comment clarifying alignment sizes > --- > tools/iio/iio_generic_buffer.c | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/tools/iio/iio_generic_buffer.c b/tools/iio/iio_generic_buffer.c > index 44bbf80f0cfd..0d0a7a19d6f9 100644 > --- a/tools/iio/iio_generic_buffer.c > +++ b/tools/iio/iio_generic_buffer.c > @@ -54,9 +54,12 @@ enum autochan { > static unsigned int size_from_channelarray(struct iio_channel_info *channels, int num_channels) > { > unsigned int bytes = 0; > - int i = 0; > + int i = 0, max = 0; > + unsigned int misalignment; > > while (i < num_channels) { > + if (channels[i].bytes > max) > + max = channels[i].bytes; > if (bytes % channels[i].bytes == 0) > channels[i].location = bytes; > else > @@ -66,6 +69,14 @@ static unsigned int size_from_channelarray(struct iio_channel_info *channels, in > bytes = channels[i].location + channels[i].bytes; > i++; > } > + /* > + * We want the data in next sample to also be properly aligned so > + * we'll add padding at the end if needed. Adding padding only > + * works for channel data which size is 2^n bytes. > + */ > + misalignment = bytes % max; > + if (misalignment) > + bytes += max - misalignment; > > return bytes; > } > > base-commit: 0bb80ecc33a8fb5a682236443c1e740d5c917d1d