Re: [PATCH v6 6/7] iio: ABI: Add custom data type

[David Lechner]

On 2/25/26 5:43 AM, Andy Shevchenko wrote:
> On Wed, Feb 25, 2026 at 11:18:06AM +0100, Francesco Lavra wrote:
>> This type is used when the data received from or sent to a device cannot be
>> identified with a standard type and must be processed by custom userspace.
>> Any driver using the custom type must provide a driver-specific document
>> that explains what the data represents and how it is to be interpreted by
>> userspace.
> 
> This rises the same Q as for other firmware-hidden algos, et cetera: How
> can we prevent the kernel from being just a simple proxy between HW and
> the userspace? What would be the point of having the "driver" in the kernel
> space?
> 

I tend to agree that this opens the door for misuse or an excuse to not
make the effort to develop something more generally useful on future drivers.

For this patch series, could we still use IIO_ROT and introduce a
new IIO_MOD_PARTIAL_QUATERNION that is defined according to the
description in the documentation patch in this series? This may be
the only driver that ever uses it, but it is still clearly defined.

Or perhaps we could even say that if a IIO_MOD_QUATERNION has
.repeat = 3 instead of .repeat = 4, then it should be interpreted
this way?