Re: [PATCH v2] arm64: dts: qcom: x1e80100-dell-xps13-9345: enable onboard accelerometers

[Aleksandrs Vinarskis]

On Tuesday, March 31st, 2026 at 19:05, Val Packett <val@xxxxxxxxxxxx> wrote:

> On 3/31/26 10:36 AM, Aleksandrs Vinarskis wrote:
> > Particular laptop comes with two sets of sensors:
> > 1. Motherboard: accelerometer
> > 2. Display/Camera module: accelerometer, ambient ligth (and more)
> >     sensor
> >
> > Both i2c busses are bound to Snapdragon Sensor Core (SSC) and are
> > typically controlled by (A)DSP thus allowing for great power
> > efficiency. This however requires DSP libraries matching ADSP firmware,
> > sensors descriptions (must be extracted from Windows) and other
> > potentially closed-source libraries. Opensource tooling includes
> > `libssc` and `hexagonrpcd`, but they were not verified to be working.
> >
> > Until SSC support for X1E lands, bitbang both i2c busses to enable
> > accelerometer functionality. In the future if/when sensors on this
> > platform can be used from DSP directly, this commit can be reverted.
> >
> > [..]
> 
> WDYM by "support lands"? It's a userspace setup thing, nothing new
> should be required in the kernel.

Hi Val,

In v1 discussion [1] it was mentioned that libssc was never tested on
X1E and is likely missing required libraries. I have briefly looked
into getting `hexagonrpcd` to run without much success (though I have 
to admit, I only spend a few hours on it). It seems just having
`hexagonrpcd` and sensors .json files (extracted from Windows) is not
enough.

> 
> It is amazing that this bitbanging works here, I don't think it was
> expected to ever work on anything newer than msm89x7 o.0

Been running it for a few weeks now without issues.

> 
> But this is likely inefficient… and "stealing" GPIOs from ADSP like this
> sounds rather scary. And would definitely break SSC initialization for
> anyone wanting to bring up hexagonrpcd/iio-sensor-proxy.

Do you have any experience with `hexagonrpcd` on X1/X1E specifically?
Personally, I think it still better to go with always-working bit-bang
approach over correctly implemented but 'needs userspace customization
and firmware' approach, as in practice it means very few people will
get it to work. However, if its possible to get SSC to run X1/X1E it
would be a very good argument to drop this patch, up to maintainers'
discretion.

Speaking more broadly, while the accelerometer is not such a highly
needed feature, ALS is, as it can be used for automatic screen brightness,
keyboard backlight controls. I am planning to port ALS's driver to get
those features next, depending on sensor model other laptops would be
able to benefit from that as well, iff bit-banging approach is chosen.

Alex

[1] https://lore.kernel.org/all/20260228-dell-xps-9345-accel-v1-1-daf9e3b3b5ee@xxxxxxxxxxxxx/

> 
> ~val
> 
>