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[2001:14ba:16f8:1500::1]) by smtp.gmail.com with ESMTPSA id eq25-20020a056512489900b004fe1f1c0ee4sm696297lfb.82.2023.09.22.04.16.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 22 Sep 2023 04:16:16 -0700 (PDT) Date: Fri, 22 Sep 2023 14:16:08 +0300 From: Matti Vaittinen To: Matti Vaittinen , Matti Vaittinen Cc: Jonathan Cameron , Lars-Peter Clausen , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Matti Vaittinen , Andy Shevchenko , Angel Iglesias , Andreas Klinger , Christophe JAILLET , Benjamin Bara , linux-iio@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v3 1/6] tools: iio: iio_generic_buffer ensure alignment Message-ID: <029b4e3e18c76b330b606f5b14699e5ee4e5ed35.1695380366.git.mazziesaccount@gmail.com> References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Spam-Status: No, score=-0.6 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on morse.vger.email Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (morse.vger.email [0.0.0.0]); Fri, 22 Sep 2023 04:16:35 -0700 (PDT) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1777737131772376322 X-GMAIL-MSGID: 1777737131772376322 The iio_generic_buffer can return garbage values when the total size of scan data is not a multiple of 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 elemnt is first in the buffer. The IIO generic buffert code does not take into accunt the last two padding bytes that are needed to ensure that the 4byte data for next scan is correctly aligned. Add padding bytes required to align the next sample into the scan size. Signed-off-by: Matti Vaittinen --- Please note, This one could have RFC in subject.: I attempted to write the fix so that the alignment is done based on the biggest channel data. This may be wrong. Maybe a fixed 8 byte alignment should be used instead? This patch can be dropped from the series if the fix is not correct / agreed. tools/iio/iio_generic_buffer.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/tools/iio/iio_generic_buffer.c b/tools/iio/iio_generic_buffer.c index 44bbf80f0cfd..fc562799a109 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 +69,16 @@ static unsigned int size_from_channelarray(struct iio_channel_info *channels, in bytes = channels[i].location + channels[i].bytes; i++; } + /* + * We wan't the data in next sample to also be properly aligned so + * we'll add padding at the end if needed. TODO: should we use fixed + * 8 byte alignment instead of the size of the biggest samnple? + */ + misalignment = bytes % max; + if (misalignment) { + printf("Misalignment %u. Adding Padding %u\n", misalignment, max - misalignment); + bytes += max - misalignment; + } return bytes; }