On Tue, 26 Nov 2019 12:56:11 +0000 Oezguen Guenyeli <oezguen.guenyeli.wg@xxxxxxxxxxx> wrote: > Hi, > I am developing Linux iio driver for one sensor and sensor provides 15 measurement samples that have to been sent the user-space for high level algorithm. > I can read data from dev/iio:device and I can apply high-level algorithm. However, I have problem about read_raw_multi function. Max_len pass value as INDIO_MAX_RAW_ELEMENTS in iio_read_channel_info function that locates in industrialio-core.c file and INDIO_MAX_RAW_ELEMENTS is defined 4 in iio.h file. > Is there any specific reason to define 4 ? Because in that way I cannot pass 15 values to user space with read_raw_multi function. Yes. The intent is that read_raw multi is used for well defined types. The largest of those that has been defined in the IIO ABI is quaternions, which have 4 elements, hence the limit. There is little point in using IIO for a device such as the one you describe as no generic userspace code is ever going to work with it. If you have a series of values that are separate well defined channels, but need to sample them in one go, then use the buffered interface and read them via a chardev. If not and there is a good reason why these 15 numbers represent one 'thing' then pitch the new userspace ABI and we can consider changing that limit. Thanks, Jonathan > > Thanks, > > Özgün Kemal Günyeli >
