On 04/14/2016 07:00 PM, Lars-Peter Clausen wrote:
On 04/14/2016 05:28 PM, Gregor Boirie wrote:
Greetings,
I'm trying to use an st_pressure based sensor to sample pressure
data using generic_buffer tool. However it seems that it does not
support data packed onto 24 bits samples.
st_pressure driver defines scan_type for my device as:
<code>
/* ... */
.scan_type = {
.sign = 'u',
.realbits = 24,
.storagebits = 24,
.endianness = IIO_LE,
},
</code>
What is the proper way to make this work ? Using 32 bits storagebits
field ? Enhance generic_buffer to support 24 bits samples ? Anything
else ??
It seems iio_compute_scan_bytes consider sample data as a simple byte
stream. So I'm wondering what are the alignment constraints for sample
start address ? Should they be aligned onto their natural "word"
boundaries, i.e. 16 bits for u16, 32 bits for u32, etc... ? And for
24 bits samples ?
IIO really only supports powers of two >= 8 for the storagebits size.
Everything else is undefined.
Samples are aligned to their storage size.
How does 24-bit alignment work?
Maybe the IIO core should check that storagebits is one of 8/16/32/64
and otherwise fail at register time? A quick grep finds only 2 drivers
using storagebits = 24 and they could easily be modified to 32.
--
Regards,
Leonard
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