linux-kernel - Re: [Linaro-acpi] How to pass I2C platform

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Message-ID: <4539649.rsMWK1FkZ6@wuerfel>
Date:	Thu, 03 Apr 2014 15:34:30 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	linaro-acpi@...ts.linaro.org
Cc:	"mika.westerberg@...ux.intel.com" <mika.westerberg@...ux.intel.com>,
	"Pallala, Ramakrishna" <ramakrishna.pallala@...el.com>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [Linaro-acpi] How to pass I2C platform_data under ACPI

On Thursday 03 April 2014 14:38:33 mika.westerberg@...ux.intel.com wrote:
> On Thu, Apr 03, 2014 at 11:25:34AM +0000, Pallala, Ramakrishna wrote:
> > >> In non ACPI environment I used to initialize the platform_data under 
> > >> board or platforms files. Under ACPI how do I do that?
> > >
> > >If you can't extract that information from ACPI namespace, then one option is to pass platform data along with the device ACPI ID:
> > >
> > >static const struct acpi_device_id my_acpi_match[] = {
> > >     { "MYID0001", (kernel_ulong_t)&my_platform_data }
> > >     ...
> > >     { },
> > >};
> > 
> > Thanks for the Quick reply.
> > 
> > So If I  want to use different platform_data for different boards can I
> > do something like below?
> 
> Exactly.
> 
> > And initialize the platform data in either driver or in separate module
> > which gets compiled along with driver?
> 
> Typically it has been done in the same driver but I don't see any problems
> having a separate module as well.
> 
> > static const struct acpi_device_id my_acpi_match[] = {
> >       { "MYID0001", (kernel_ulong_t)&my_platform_data1 }
> >       { "MYID0002", (kernel_ulong_t)&my_platform_data2 }
> >       ...
> >       { },

We definitely don't want per-board match entries, that does not scale.
The driver should be reasonably generic and get all the necessary data
out of well-defined tables. You can have different IDs when there
are only a few cases that are actually relevant, but it has to be
conceivable that the same driver get used on future hardware without
changes.

	Arnd
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