linux-kernel - Re: [PATCH] i2c: Make I2C ID tables non-mandatory for DT'ed and/or ACPI'ed devices

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Date:	Wed, 04 Jun 2014 08:09:31 +0200
From:	Michael Lawnick <ml.lawnick@....de>
To:	Linus Walleij <linus.walleij@...aro.org>
CC:	Wolfram Sang <wsa@...-dreams.de>,
	Grant Likely <grant.likely@...aro.org>,
	Lee Jones <lee.jones@...aro.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>
Subject: Re: [PATCH] i2c: Make I2C ID tables non-mandatory for DT'ed and/or
 ACPI'ed devices

Am 03.06.2014 13:18, schrieb Linus Walleij:
> On Mon, Jun 2, 2014 at 4:29 PM, Michael Lawnick <ml.lawnick@....de> wrote:
>> Am 02.06.2014 14:16, schrieb Linus Walleij:
>
>>> Is this really so useful on embedded systems?
>>>
>>> I was under the impression that this method was something used
>>> on say PC desktops with temperature monitors and EEPROMs
>>> on some I2C link on the PCB, usage entirely optional and fun
>>> for userspace hacks.
>>>
>> We use it for dynamic instantiating whole subsystems with multiplexers,
>> sensors, controllers in an embedded system. The device list is taken from an
>> I2C eeprom which gets read on hotplug.
>
> Does this mean that you have stored the names (strings) that are used
> by the Linux kernel for identifying the devices into your EEPROM?
>
> That means that you have made the kernel-internal device driver names
> an ABI which is unfortunate :-/
>
> This is one of the reasons to why we insist on device tree: OS neutral
> hardware description.

The eeprom contains a device tree that is dynamically merged.

KR
Michael


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