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

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Message-ID: <20231223125350.xqggx3nyzyjjmnut@pali>
Date: Sat, 23 Dec 2023 13:53:50 +0100
From: Pali Rohár <pali@...nel.org>
To: Hans de Goede <hdegoede@...hat.com>
Cc: Paul Menzel <pmenzel@...gen.mpg.de>, Jean Delvare <jdelvare@...e.com>,
	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 Saturday 23 December 2023 13:45:32 Hans de Goede wrote:
> 2. Add a "probe_i2c_address" bool module option and when this
>    is set try to read the WHO_AM_I register, see
>    drivers/misc/lis3lv02d/lis3lv02d.c
>    and if this succeeds and gives a known model id then
>    continue with the found i2c_address. This should first
>    try address 0x29 which seems to be the most common and
>    then try 0x18 and then give up.

This is the main problem of the whole email thread. How to figure out
the correct smbus device address.

And we really must not poke random address during kernel boot time.
I think in the past was there enough problems linux kernel broke some HW
or made system unbootable just because it tried to read something from
some random undocumented address.

Please do not try random unverified address on all machines.

smbus is not really bus which provides discovering and identifying
devices on the bus.