linux-kernel - Re: [PATCH v2 1/1] Platform: x86: Add Chrome OS Laptop driver

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Date:	Fri, 2 Nov 2012 14:09:27 +0100
From:	Olof Johansson <olof@...om.net>
To:	Corentin Chary <corentin.chary@...il.com>
Cc:	Benson Leung <bleung@...omium.org>,
	Matthew Garrett <mjg@...hat.com>,
	"platform-driver-x86@...r.kernel.org" 
	<platform-driver-x86@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>, olofj@...omium.org
Subject: Re: [PATCH v2 1/1] Platform: x86: Add Chrome OS Laptop driver

On Fri, Nov 2, 2012 at 2:03 PM, Corentin Chary <corentin.chary@...il.com> wrote:
> On Fri, Nov 2, 2012 at 12:45 PM, Olof Johansson <olof@...om.net> wrote:
>> On Fri, Oct 26, 2012 at 10:30 AM, Corentin Chary
>> <corentin.chary@...il.com> wrote:
>>
>>> Looks better, but I'm curious, what is the final purpose of this driver ?
>>> What ABI will be exposed, who will use it ?
>>>
>>> If it is going to be bigger, it may be a good idea to convert it to a
>>> real platform driver (platform_drivers/platform_device stuff).
>>
>> It's not a driver per se. It's platform glue that, based on the DMI
>> table, registers platform and i2c devices (at this time only i2c
>> devices).
>>
>> Unfortunately there's no way to do this nicely from userspace after
>> boot, since there's limits to how much data you can provide with the
>> simpler userspace-driven i2c probing protocol.
>>
>> So, there's no user-facing ABI on this, and no one is expected to use
>> it from userspace. It's just there to make sure that the un-probably
>> devices on this kind of hardware gets bound to drivers properly.
>>
>> If it's converted to a platform_driver, how do you expect that to
>> probe, where would the platform_device be registered?
>
> I guess I would check dmi in the module init method, and then use the
> probe callback of platform_create_bundle to do more probing if
> necessary.

Maybe I'm dense but I don't see how that could possibly be better than
what the code does today. It would just add more overhead and clutter
by creating a unnecessary dummy device/driver setup just to, in the
end, register the same i2c devices.


-Olof
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