linux-kernel - Re: [PATCH] RFC: pinctrl: grab default handler with bus notifiers

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Message-ID: <CACRpkdYd6B-fTfUg18q5BjZRbY7sUAUNXA_7VPBs9SQoug9Q4w@mail.gmail.com>
Date:	Fri, 16 Nov 2012 12:36:33 +0100
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Stephen Warren <swarren@...dotorg.org>
Cc:	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Linus Walleij <linus.walleij@...ricsson.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Stephen Warren <swarren@...dia.com>,
	Anmar Oueja <anmar.oueja@...aro.org>,
	Felipe Balbi <balbi@...com>, Benoit Cousson <b-cousson@...com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Mitch Bradley <wmb@...mworks.com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Kevin Hilman <khilman@...com>,
	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>,
	Rickard Andersson <rickard.andersson@...ricsson.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Russell King <linux@....linux.org.uk>
Subject: Re: [PATCH] RFC: pinctrl: grab default handler with bus notifiers

On Thu, Nov 15, 2012 at 7:23 PM, Stephen Warren <swarren@...dotorg.org> wrote:
> On 11/15/2012 07:03 AM, Linus Walleij wrote:

>> OK I'll have to come up with a patch to the device core
>> instead... it'll be much simpler anyway and if both of you guys
>> can back it I guess Greg might be OK with it too.
>
> I did have one thought here; how will this interact with hogs? If a
> device's pinctrl configuration must be pinctrl_get()'d before the device
> is probed, then a pinctrl device with hogs will never get probed because
> it won't be registered to provide the pinctrl node parsing.

Catch 22 :-(

Yeah we need to come up with something there.

> Solutions might include:
>
> a) Some special case where if the pinctrl driver only can't probe due to
> missing pinctrl from its own node, don't defer the probe, but defer the
> pinctrl_get().
>
> b) Separate out DT node parsing from device instantiation, so that the
> driver can always parse the DT, without needing the context of a
> specific pinctrl device to do so.

But this mechanism can't be device tree-specific, we have some
of olschool pdata users and ACPI probing around the corner.

I will likely just cook up something like seeing if the
dev_name() for provider and consumer is the same and
in that case avoid deferral.

Oh well, I'll try to actually code this now...

Yours,
Linus Walleij
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