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The dmaengine buffer has some length alignment requirements that can differ from platform to platform. If the length alignment requirements are not met unexpected behavior like dropping of samples can occur. Currently these requirements are not reported and applications need to know the requirements of the platform by some out-of-band means. Add a new buffer attribute that reports the length alignment requirements called `length_align_bytes`. The reported length alignment is in bytes that means the buffer length alignment in sample sets depends on the number of enabled channels and the bytes per channel. Applications using this attribute to determine the buffer size requirements need to consider this. Signed-off-by: Lars-Peter Clausen <lars@metafoo.de> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
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What: /sys/bus/iio/devices/iio:deviceX/buffer/length_align_bytes KernelVersion: 5.4 Contact: linux-iio@vger.kernel.org Description: DMA buffers tend to have a alignment requirement for the buffers. If this alignment requirement is not met samples might be dropped from the buffer.
This property reports the alignment requirements in bytes.
This means that the buffer size in bytes needs to be a integer
multiple of the number reported by this file.
The alignment requirements in number of sample sets will depend
on the enabled channels and the bytes per channel. This means
that the alignment requirement in samples sets might change
depending on which and how many channels are enabled. Whereas
the alignment requirement reported in bytes by this property
will remain static and does not depend on which channels are
enabled.