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

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Message-ID: <20240213150708.57148f6a@endymion.delvare>
Date: Tue, 13 Feb 2024 15:07:08 +0100
From: Jean Delvare <jdelvare@...e.de>
To: Pali Rohár <pali@...nel.org>
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 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