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From: Olof Johansson <>
To: Jochen Friedrich <>
Cc: Jean Delvare <>,,
	linuxppc-dev list <>,, Scott Wood <>
Subject: Re: [PATCHv4 2.6.25] i2c: adds support for i2c bus on Freescale CPM1/CPM2 controllers
Date: Sun, 24 Feb 2008 12:15:10 -0600	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>


On Sun, Feb 24, 2008 at 04:16:30PM +0100, Jochen Friedrich wrote:
> Hi Olof,
> >> 2. record the I2c name in the dts tree, either as seperate tag (like linux,i2c-name="<i2c-name>")
> >>    or as additional compatible entry (like compatible="...", "linux,<i2c-name>").
> > 
> > I have to say no on this one. The device tree is not supposed to know
> > about how linux uses devices, there are firmwares out there that don't
> > use DTS for thier device trees, etc.
> I still believe this this could be done for embedded devices which are usually booted
> via wrapper or U-Boot as those devices will most probably use the most exotic I2c devices
> out there (e.g. home-grown devices used by stbs). However, I'm not an device tree expert.

Sorry, but you're wrong in your assumptions. Not all embedded devices
use U-boot, and not all use the wrapper. It's just a bad idea to encode
linux-specific things in the device tree, period.

And even if you DO decide to go that route, guess what? You need a
translation table just as with (3) anyway!

> >> 3. use a glue layer with a translation map.
> > 
> > In my opinion this is an OK solution since the same information has to
> > be added somewhere already anyway -- eiither to the drivers or to this
> > translation table. It should of course be an abstacted shared table,
> > preferrably contained under the i2c source directories since several
> > platforms and architectures might share them.
> I could think of a mixture between 2. and 3.:
> Using the compatible attribute with the manufacturer stripped off as I2c name by default
> and using an exception table. For now, the struct i2c_driver_device would currently only
> need one entry ("dallas,ds1374", "rtc-ds1374").

You still need the translation table, you're just flattening the
namespace to one string instead of two, the same information still has
to be encoded. I can't see what the benefit of this approach compared to
the other one is. "dallas,ds1374" already only has one translation entry
in the table?


  reply	other threads:[~2008-02-24 18:11 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-01-31 12:54 Jochen Friedrich
2008-02-21 12:05 ` Jean Delvare
2008-02-22 11:16   ` Jochen Friedrich
2008-02-23 12:43     ` Jean Delvare
2008-03-25 18:46       ` Jochen Friedrich
2008-03-26  0:41         ` Stephen Rothwell
2008-02-23 21:28     ` Olof Johansson
2008-02-24 15:16       ` Jochen Friedrich
2008-02-24 18:15         ` Olof Johansson [this message]
2008-02-25 16:48           ` Jochen Friedrich
2008-02-24 16:19     ` Jon Smirl

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