linux-kernel - Re: [PATCH 2/2] i2c-designware-pci: Index Haswell ULT bus names from 0

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Message-ID: <20131126130959.GI7427@katana>
Date:	Tue, 26 Nov 2013 14:09:59 +0100
From:	Wolfram Sang <wsa@...-dreams.de>
To:	Benson Leung <bleung@...omium.org>
Cc:	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	khali@...ux-fr.org, andriy.shevchenko@...ux.intel.com,
	jacmet@...site.dk, linux-i2c@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Duncan Laurie <dlaurie@...omium.org>
Subject: Re: [PATCH 2/2] i2c-designware-pci: Index Haswell ULT bus names from
 0

On Tue, Nov 19, 2013 at 06:14:18PM -0800, Benson Leung wrote:
> Hi Wolfram,
> 
> On Thu, Nov 14, 2013 at 10:05 AM, Wolfram Sang <wsa@...-dreams.de> wrote:
> >> In the chromeos_laptop driver, I do by-name matching of i2c busses to
> >> find busses and instantiate devices, so there is value to have each
> >> named something predictable.
> >
> > Any why don't you use fixed bus numbers which you can attach the devices
> > to?
> 
> On this particular set of systems, there are two other classes of i2c
> adapters that use dynamically assigned bus numbers, specifically the
> i915 gmbus adapters, and the i801_smbus adapter. This is why
> chromeos_laptop uses the name matching, as some of the boards that it
> supports have devices on those dynamic busses.

I am not sure I get the problem. If you use i2c_register_board_info() to
register the known devices on the designware busses the dynamically
assigned numbers are guaranteed to be enumarated higer than the static
ones. Check drivers/i2c/i2c-boardinfo.c.

Regards,

   Wolfram


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