Re: [PATCH 1/2] dt-bindings: iio: imu: mpu6050: Document invensense,icm20608d

From: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
To: Michael Srba <Michael.Srba@seznam.cz>,
	Jonathan Cameron <jic23@kernel.org>,
	Lars-Peter Clausen <lars@metafoo.de>,
	Rob Herring <robh+dt@kernel.org>
Cc: Jean-Baptiste Maneyrol <jmaneyrol@invensense.com>,
	linux-iio@vger.kernel.org, devicetree@vger.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: iio: imu: mpu6050: Document invensense,icm20608d
Date: Thu, 10 Mar 2022 22:24:03 +0100	[thread overview]
Message-ID: <145bddd6-0a7e-95f4-5282-b1900f020d88@canonical.com> (raw)
In-Reply-To: <2af7be38-7784-96af-aa3f-84b87d983b38@seznam.cz>

On 10/03/2022 19:56, Michael Srba wrote:
> Hi,
> the thing is, the only reason the different compatible is needed at all
> is that the chip presents a different WHOAMI, and the invensense,icm20608
> compatible seems to imply the non-D WHOAMI value.

But this is a driver implementation issue, not related to bindings.
Bindings describe the hardware.

> I'm not sure how the driver would react to both compatibles being present,
> and looking at the driver code, it seems that icm20608d is not the only
> fully icm20608-compatible (to the extent of features supported by
> the driver, and excluding the WHOAMI value) invensense IC, yet none
> of these other ICs add the invensense,icm20608 compatible, so I guess I
> don't see a good reason to do something different.

Probably my question should be asked earlier, when these other
compatibles were added in such way.

Skipping the DMP core, the new device is fully backwards compatible with
icm20608. Therefore extending the compatible makes sense. This is not
only correct from devicetree point of view, but also is friendly towards
out of tree users of bindings.

The Linux driver behavior about whoami register does not matter here.
Not mentioning that it would be easy for driver to accept multiple
values of whoami.

Best regards,
Krzysztof