linux-kernel - Re: Ideas for a generic solution to support accelerometer lis3lv02d in Dell laptops/notebooks?

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Date: Thu, 15 Feb 2024 19:16:33 +0100
From: Pali Rohár <pali@...nel.org>
To: Jean Delvare <jdelvare@...e.de>
Cc: Hans de Goede <hdegoede@...hat.com>,
	Paul Menzel <pmenzel@...gen.mpg.de>,
	Andi Shyti <andi.shyti@...nel.org>, Wolfram Sang <wsa@...nel.org>,
	linux-i2c@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	Kai-Heng Feng <kai.heng.feng@...onical.com>,
	Marius Hoch <mail@...iushoch.de>,
	Mario Limonciello <mario.limonciello@....com>,
	Dell.Client.Kernel@...l.com, Greg KH <gregkh@...uxfoundation.org>
Subject: Re: Ideas for a generic solution to support accelerometer lis3lv02d
 in Dell laptops/notebooks?

On Tuesday 13 February 2024 15:07:08 Jean Delvare wrote:
> On Sat, 23 Dec 2023 13:53:50 +0100, Pali Rohár wrote:
> > smbus is not really bus which provides discovering and identifying
> > devices on the bus.
> 
> For completeness, SMBus version 2.0 actually added support for device
> discovery and even dynamic slave address allocation. This is explained
> in chapter 5, section 5.6 (SMBus Address resolution protocol).
> 
> Unfortunately, this is an optional feature which requires active
> cooperation from each device connected to the bus. If any device on the
> bus supports SMBus ARP then you should get an answer when probing
> (7-bit) I2C address 0x61.
> 
> Long ago I had a plan to add support for SMBus ARP to the kernel, but
> gave up because I couldn't find any system implementing it. If the
> accelerometer device in Dell laptops supported ARP then we could use it
> to figure out the device's address, unfortunately this doesn't seem to
> be the case.
> 
> -- 
> Jean Delvare
> SUSE L3 Support

According to my notes, accelerometer in Dell laptops should use
LNG3DMTR-LGA16-3x3 chipset. From what I found it should be
pin-compatible with LIS302DL, just in different package.

ST LIS302DL datasheet is on the website:
https://www.st.com/resource/en/datasheet/lis302dl.pdf

It is dual i2c and SPI bus support chipset. But in the datasheet there
is nothing about SMBus, looks like this is designed for i2c usage. So I
highly doubt that chipset supports SMBus version 2.0 with ARP extension.

Anyway, SMBus ARP is new thing to me, I have never heard about it or its
usage before. Has anybody else found some device which supports it?
Would be interesting to know if this is not just another standard which
was not publicly deployed yet.