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[2001:14ba:16f8:1500::7]) by smtp.gmail.com with ESMTPSA id l19-20020a19c213000000b005042ae2baf8sm132270lfc.258.2023.10.03.02.57.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Oct 2023 02:57:55 -0700 (PDT) Date: Tue, 3 Oct 2023 12:57:47 +0300 From: Matti Vaittinen To: Matti Vaittinen , Matti Vaittinen Cc: Jonathan Cameron , Lars-Peter Clausen , linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v6] tools: iio: iio_generic_buffer ensure alignment Message-ID: MIME-Version: 1.0 Content-Disposition: inline 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 groat.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 (groat.vger.email [0.0.0.0]); Tue, 03 Oct 2023 02:58:31 -0700 (PDT) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1778650171059511892 X-GMAIL-MSGID: 1778727899783198486 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.") --- 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(-) base-commit: 0bb80ecc33a8fb5a682236443c1e740d5c917d1d 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; }