linux-kernel - Re: [PATCH 2/3] spi / ACPI: add ACPI enumeration support

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Message-ID: <20121105161920.44e8e1cb@endymion.delvare>
Date:	Mon, 5 Nov 2012 16:19:20 +0100
From:	Jean Delvare <khali@...ux-fr.org>
To:	Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linus Walleij <linus.walleij@...aro.org>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	linux-kernel@...r.kernel.org, lenb@...nel.org,
	rafael.j.wysocki@...el.com, grant.likely@...retlab.ca,
	ben-linux@...ff.org, w.sang@...gutronix.de,
	mathias.nyman@...ux.intel.com, linux-acpi@...r.kernel.org
Subject: Re: [PATCH 2/3] spi / ACPI: add ACPI enumeration support

On Mon, 5 Nov 2012 16:53:15 +0200, Mika Westerberg wrote:
> On Mon, Nov 05, 2012 at 03:19:58PM +0100, Rafael J. Wysocki wrote:
> > 
> > In the ACPI namespace we have device nodes and serial interfaces below them.
> > In the above case we see that a single device node supports two different
> > interfaces and in that case we probably should create two different
> > struct i2c_adapter objects for the same ACPI device node.
> > 
> > Mika, what do you think?
> 
> I agree.
> 
> Only problem I see is that then we have two I2C adapter devices with the
> same ACPI ID (and hence the same i2c_client->name). I wonder what the I2C
> core thinks about that.

I2C core fears that you're mixing up everything ;) I2C adapter devices
are struct i2c_adapter aka i2c-0, i2c-1 etc. i2c_client is for slave
devices. There's nothing wrong with i2c_clients sharing ->name, that's
even how device driver matching is achieved. The uniqueness of
i2c_clients is on their bus_id which is the combination of i2c adapter
number and slave address (e.g. 0-0050)

i2c_adapter->name should, OTOH, be unique. In i2c bus drivers we
usually append the base I/O address at the end of the name to guarantee
that. ACPI will have to come up with something similar.

-- 
Jean Delvare
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