iio: Understanding the modes

[Miquel Raynal <miquel.raynal@bootlin.com>]

Hello IIO folks,

I am currently writing a blog post trying to explain the situation that
I had with the max1027 driver [1] and possibly try to explain the logic
behind the changes that Jonathan/Nuno requested. As part of this work, I
tried to understand (and explain?) the meaning of the mode definitions
and if they were needed or not, but just looking at the code was not
enough for me to really understand.

While digging into the IIO core, I realized that many definitions and
helpers had no comments explaining their use. I could not find any
documentation about the kernel API in general neither (while the
userspace side is well documented).

I asked yesterday on #linux-iio but got no answers so I am also asking
here in case there are knowledgeable people willing to explain what
each of these definition actually mean and how they should be used:
https://elixir.bootlin.com/linux/latest/source/include/linux/iio/iio.h#L319

I am ready to send a patch upstream to add the necessary comment
so that these explanations do not stay on the mailing list only.

Thanks,
Miquèl

[1] https://lore.kernel.org/linux-iio/20210918180918.6908bbd9@jic23-huawei/