linux-kernel - Re: [PATCH 3/3] iio: imu: st_lsm6dsx: add support for rotation sensor

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Message-ID: <43a8feadc9326c35bde8da12d4045ba61be97051.camel@baylibre.com>
Date: Fri, 16 Jan 2026 20:26:56 +0100
From: Francesco Lavra <flavra@...libre.com>
To: Jonathan Cameron <jic23@...nel.org>
Cc: Lorenzo Bianconi <lorenzo@...nel.org>, David Lechner
 <dlechner@...libre.com>,  Nuno Sá <nuno.sa@...log.com>,
 Andy Shevchenko <andy@...nel.org>,  linux-iio@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] iio: imu: st_lsm6dsx: add support for rotation
 sensor

On Fri, 2026-01-16 at 18:27 +0000, Jonathan Cameron wrote:
> 
> > 
> > > > +       const struct st_lsm6dsx_reg *mux;
> > > > +       int err;
> > > > +
> > > > +       mux = &hw->settings->sf_settings.page_mux;  
> > > 
> > > Just to check, can you use regmaps support for paging instead of
> > > doing
> > > this by hand?
> > > That would avoid future problems with enabling caching or similar  
> > 
> > No, the chip has multiple register sets with overlapping addresses, and
> > struct regmap_range_cfg is not usable here.
> 
> Paged addressing always has overlapping addresses, so I'm not following.
> The trick this does is to map those higher pages to a fake set of
> addresses.

I thought having a fake set of addresses in the driver would be frowned
upon since it would create a mismatch between the code and the device
datasheet. But I guess it wouldn't be so bad if appropriate offsets between
register pages are chosen.
Anyway, as you noted in this case the different pages cannot be selected
via a simple bank selector register.

> An example is the ICM42600:
> https://invensense.tdk.com/wp-content/uploads/2020/04/ds-000347_icm-42688-p-datasheet.pdf
> for a suitable datasheet (some of the newer parts have a much more
> complex scheme)
> 
> I took a look at the datasheet and seems there are multiple types of
> paging
> going on and effectively ends up with two nested paging controls. So fair
> enough it
> doesn't fit here.


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