Commit b003b7a7 authored Oct 03, 2023 by Matti Vaittinen Committed by Greg Kroah-Hartman Nov 20, 2023

tools: iio: iio_generic_buffer ensure alignment



[ Upstream commit 2d3dff577dd0ea8fe9637a13822f7603c4a881c8 ]

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 <mazziesaccount@gmail.com>
Fixes: e58537cc ("staging: iio: update example application.")
Link: https://lore.kernel.org/r/ZRvlm4ktNLu+qmlf@dc78bmyyyyyyyyyyyyydt-3.rev.dnainternet.fi


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent 7a64d15d

tools/iio/iio_generic_buffer.c

+12 −1

Original line number	Diff line number	Diff line
		@@ -52,9 +52,12 @@ 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
		@@ -64,6 +67,14 @@ 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;
		}