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tools: iio: iio_generic_buffer ensure alignment

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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: e58537ccce ("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>
This commit is contained in:
Matti Vaittinen 2023-10-03 12:57:47 +03:00 committed by Jonathan Cameron
parent 848f68c760
commit 2d3dff577d
1 changed files with 12 additions and 1 deletions
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13
tools/iio/iio_generic_buffer.c
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@ -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;
}