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

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Message-ID: <20240227205115.szb32h7hxjjr6z3l@pali>
Date: Tue, 27 Feb 2024 21:51:15 +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 Thursday 15 February 2024 19:16:33 Pali Rohár wrote:
> 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.

Now I checked i2c address 0x61 and nothing responds to it.

> 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.