linux-kernel - Re: [PATCH 1/3] MFD: introduce lpc

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Message-ID: <4B7BBEE5.3040104@compulab.co.il>
Date:	Wed, 17 Feb 2010 12:03:17 +0200
From:	Denis Turischev <denis@...pulab.co.il>
To:	Jean Delvare <khali@...ux-fr.org>
CC:	David Brownell <david-b@...bell.net>,
	LKML <linux-kernel@...r.kernel.org>,
	Samuel Ortiz <sameo@...ux.intel.com>, linux-i2c@...r.kernel.org
Subject: Re: [PATCH 1/3] MFD: introduce lpc_sch for Intel SCH LPC bridge

Jean Delvare wrote:
> On Tue, 16 Feb 2010 11:57:46 -0800, David Brownell wrote:
>> On Thursday 11 February 2010, Denis Turischev wrote:
>>> Intel Poulsbo (SCH) chipset LPC bridge controller contains several
>>> functions. Creating and MFD driver for the LPC bridge controller allows
>> Spelling nit: "Creating an" (not and).  Keyboard, brain, or edit fault.  ;)
>>
>>
>>> simultaneous use of SMBus and GPIO interfaces on the SCH.
>> This looks like the right way to package such southbridge level
>> componentry.  Maye not just these two interfaces, either.
>>
>> But ... how does this play with ACPI?  The last several Intel
>> systems I looked at seemed to expect ACPI to manage GPIOs and the
>> IRQs they may issue.  (He wrote, staring at an ICH8-system where
>> ACPI uses GPIOs to manage several buttons and LEDs.)
>>
>> It would seem error-prone to ignore that coupling on systems
>> with ACPI.  Linux has enough trouble sorting out issues caused
>> by buggy AML (ACPI bytecode) without introducing conflicts in
>> who manages which hardware resource (ACPI vs. operating system).
> 
> Might be a good idea to use acpi_check_resource_conflict() or similar
> before instantiating the platform devices.

May be it worth to add such resource check directly to mfd_add_device function?

> 
>> Of course, if ACPI weren't being used to hide such board-specific
>> details from operating systems, such issues would not exist.  But
>> such hiding is one of the basic goals of ACPI ... annoying.
> 
> Don't start me on this :(
> 

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