linux-kernel - Re: [PATCHv3 1/4] mfd: smsc: Add support for smsc gpio io/keypad driver

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Date:	Wed, 3 Oct 2012 00:42:12 +0530
From:	"ABRAHAM, KISHON VIJAY" <kishon@...com>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Cc:	Sourav Poddar <sourav.poddar@...com>,
	devicetree-discuss@...ts.ozlabs.org,
	linux-arm-kernel@...ts.infradead.org, linux-omap@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
	b-cousson@...com, balbi@...com, santosh.shilimkar@...com,
	sameo@...ux.intel.com
Subject: Re: [PATCHv3 1/4] mfd: smsc: Add support for smsc gpio io/keypad driver

Hi,

On Tue, Oct 2, 2012 at 6:08 PM, Mark Brown
<broonie@...nsource.wolfsonmicro.com> wrote:
> On Mon, Oct 01, 2012 at 08:54:23PM +0530, ABRAHAM, KISHON VIJAY wrote:
>> On Mon, Oct 1, 2012 at 5:39 PM, Mark Brown
>
>> > Why would that be helpful?  Most platforms don't support DT at all, and
>
>> I'm not sure how to put it correctly. All I'm trying to tell is mfd is
>> a framework that exposes a set of API's to create and remove a device
>> among others. If a mfd child device is not created using mfd API,
>> it'll be unfair to expect that child be removed properly using mfd
>> API. Like in this patch, the device is created using
>> of_platform_populate (not a mfd API) but is removed using
>> mfd_remove_devices (mfd API) [which should result in an abort].
>
> That doesn't sound terribly clever, no, though it's not immediately
> clear to me if the non-clever bit is using mfd_remove_devices() or
> of_platform_populate().
>
>> This means mfd framework does not have an API to create a device from
>> dt data or so do I think since of_platform_populate() is used. Thats
>> why I suggested the idea of extending mfd_add_devices() (or adding a
>> new API in mfd framework) to create child devices from dt data so that
>> we'll have API's in mfd framework to both create and delete a device.
>
> The trouble that always exists with representing MFD children in DT is
> that unless you've got a usefully reusable IP block which is clearly
> separate from the chip integration you end up essentially just dumping
> the Linux data structures into DT which often doesn't leave you with
> something which describes the hardware.

indeed!

Thanks
Kishon
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