linux-kernel - Re: [PATCH, RFC] Earlier I2C initialization

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Date:	Mon, 30 Jun 2008 08:34:14 +1200
From:	Ryan Mallon <ryan@...ewatersys.com>
To:	Jean Delvare <khali@...ux-fr.org>
CC:	David Brownell <david-b@...bell.net>,
	Uli Luckas <u.luckas@...d.de>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	i2c@...sensors.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH, RFC] Earlier I2C initialization

Jean Delvare wrote:
> Hi Ryan,
> 
> On Fri, 27 Jun 2008 09:12:54 +1200, Ryan Mallon wrote:
>> Jean Delvare wrote:
>>> I don't like option 2 at all. drivers/i2c/early could be, but not
>>> drivers/i2c-early.
>> I don't think its a good idea either. The point was that in order to
>> have two sets of i2c drivers with different link order (with regard to
>> the rest of the driver subsystems) you would need two top level
>> directories in drivers/.
> 
> I don't think so. Look at what the input subsystem does (from
> drivers/Makefile):
> 
> obj-$(CONFIG_SERIO)		+= input/serio/
> obj-$(CONFIG_GAMEPORT)		+= input/gameport/
> obj-$(CONFIG_INPUT)		+= input/
> 
> And there are similar examples with video (video/i810/ and
> video/intelfb/ are early in the list). 

Ah, didn't realise that.

>We could do the same with i2c:
> 
> obj-$(CONFIG_I2C)		+= i2c/early/
> 
> (... lots of things ...)
> 
> obj-$(CONFIG_I2C)		+= i2c/
> 
> Of course this implies minor edits to drivers/i2c/Makefile. I don't
> know if we want to do that, but from a technical point of view it seems
> doable.

That certainly is a better solution if it is needed.

> 
>> The other way of course, is to use one
>> directory, or subdirectories under drivers/i2c/ and use subsys_initcall.

Yeah, its probably the best solution for now. Doing the categorisation
of the busses will make it easy to split the directories/link order up
later if required.

>>> (...)
>>> If we are going to keep using subsys_initcall in bus drivers, then
>>> moving the bus drivers using it to a separate directory is not needed.
>>> Which doesn't mean we don't want to split the i2c bus drivers into
>>> subdirectories for other reasons, but I want to see this as a separate
>>> issue. BTW, I started categorizing the different types of i2c bus
>>> drivers:
>>> http://khali.linux-fr.org/devel/linux-2.6/jdelvare-i2c/i2c-group-bus-drivers.patch
>>> If you want to help with embedded stuff or SOC or whatever makes sense
>>> to group together, please do! For now, everything I am not familiar
>>> with is in group "Others".
>> I don't know all of the embedded systems, but at a glance the following
>> busses from your others section are used on embedded ARM processors:
>>
>> i2c-at91
>> i2c-davinci
>> i2c-ixp2000
>> i2c-omap
>> i2c-pxa
>> i2c-s3c2410
>> i2c-versatile
> 
> OK, I've moved these to a section titled "Embebbed system I2C host
> controller drivers", thanks.

Cool.

~Ryan

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