linux-kernel - Re: [PATCH v2 1/7] dt-bindings: iio: BU27034 => BU27034ANUC

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Message-ID: <20240708-tropical-stifle-0aca848ad340@spud>
Date: Mon, 8 Jul 2024 18:06:35 +0100
From: Conor Dooley <conor@...nel.org>
To: Matti Vaittinen <mazziesaccount@...il.com>
Cc: Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
	Jonathan Cameron <jic23@...nel.org>,
	Lars-Peter Clausen <lars@...afoo.de>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, linux-iio@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/7] dt-bindings: iio: BU27034 => BU27034ANUC

On Fri, Jul 05, 2024 at 01:54:12PM +0300, Matti Vaittinen wrote:
> The BU27034NUC was cancelled before it entered mass production. It was
> replaced by a new variant BU27034ANUC (note, added 'A'). The new
> variant gained a few significant changes, like removal of the 3.rd data
> channel and dropping some of the gain settings. This means that, from
> software point of view these ICs are incompatible. Lux calculation based
> on the data from the sensors needs to be done differently, and on the
> BU27034ANUC the channel 3 data is missing. Also, the gain setting
> differencies matter.
> 
> Unfortunately, the identification register was not changed so there is no
> safe way for the software to distinguish the variants.
> 
> According to the ROHM HQ engineers, the old BU27034NUC should not be
> encountered in the wild. Hence it makes sense to remove the support for
> the old BU27034NUC and add support for the new BU27034ANUC. Change the
> compatible in order to not load the incompatible old driver for new sensor
> (or, if someone had the old sensor, the new driver for it).
> 
> Drop the compatible for old sensor which should not be in the wild and
> add a new compatible for the new model with accurate model suffix
> 'anuc'.

Since you say that the "old" device should never be encountered "in the
wild", this change seems fine. If it turns out that it is in the wild,
the new compatible means we could resurrect the old driver etc.

Acked-by: Conor Dooley <conor.dooley@...rochip.com>

Cheers,
Conor.

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