5.4-stable review patch. If anyone has any objections, please let me know.
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From: Matti Vaittinen mazziesaccount@gmail.com
[ 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: e58537ccce73 ("staging: iio: update example application.") Link: https://lore.kernel.org/r/ZRvlm4ktNLu+qmlf@dc78bmyyyyyyyyyyyyydt-3.rev.dnain... Signed-off-by: Jonathan Cameron Jonathan.Cameron@huawei.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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 e38c72fd58ccf..2fd10eab75b53 100644 --- a/tools/iio/iio_generic_buffer.c +++ b/tools/iio/iio_generic_buffer.c @@ -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; }