Re: [PATCH V4 01/10] dt-bindings: iio: imu: icm42600: Add icm42607 binding

[Jonathan Cameron <jic23@kernel.org>]

On Sun, 3 May 2026 15:51:30 -0500
Chris Morgan <macromorgan@hotmail.com> wrote:

> On Sun, May 03, 2026 at 02:18:18PM +0200, Krzysztof Kozlowski wrote:
> > On Fri, May 01, 2026 at 05:11:40PM -0500, Chris Morgan wrote:  
> > > From: Chris Morgan <macromorgan@hotmail.com>
> > > 
> > > Add devicetree binding for the Invensense ICM42607 and Invensense
> > > ICM42607P inertial measurement unit. This unit is a combined
> > > accelerometer, gyroscope, and thermometer available via I2C or SPI.
> > > 
> > > This device is functionally very similar to the icm42600 series with a
> > > very different register layout. Additionally, add mount-matrix
> > > attribute to schema.  
> > 
> > Why adding it? Is it something new? Is it applicable to other variants?
> > If not, why it is allowed for them?  
> 
> It's not new, technically this is a bug/oversight from the very first
> iteration of the invensense icm42600 driver. The driver requests a
> mount matrix using iio_read_mount_matrix and then returns an error from

Unless it's broken (always possible) iio_read_mount_matrix() is supposed
to return an identity matrix if there isn't any info in the binding.

	/* Matrix was not declared at all: fallback to identity. */
	return iio_setup_mount_idmatrix(dev, matrix);

So not required by the linux driver at least.  Probably not something
we should require in general.

Separate patch to introduce it to the binding as optional and say something
about what it is for to justify it's inclusion.  That patch goes before
this one.

> the probe function if it can't read one [1]. So it's very much required
> (and for the next version I'll upgrade it to a required element). I'm
> adding it because a cursory grep suggests that my use case (for the
> Anbernic RG-DS and in the near future the Anbernic RG Vita Pro) are the
> first devices to use this driver in mainline in a device tree based
> system.
> 
> Thank you,
> Chris
> 
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/iio/imu/inv_icm42600/inv_icm42600_core.c?h=v7.1-rc1#n746
> 
> > 
> > Do not say WHAT you did, say why you did it.
> > 
> > Best regards,
> > Krzysztof
> >