linux-kernel - Re: [RFC PATCH 0/2] DT match helpers for initcalls and platform devices

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Message-ID: <CAL_JsqKna00oyhSd0qTYfLVFeE6d-gbekmV9tg7raPxmCTsYHQ@mail.gmail.com>
Date:	Wed, 30 Oct 2013 16:40:38 -0500
From:	Rob Herring <robherring2@...il.com>
To:	Thierry Reding <thierry.reding@...il.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Grant Likely <grant.likely@...aro.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Rob Herring <rob.herring@...xeda.com>
Subject: Re: [RFC PATCH 0/2] DT match helpers for initcalls and platform devices

On Wed, Oct 30, 2013 at 3:02 PM, Rob Herring <robherring2@...il.com> wrote:
> On Wed, Oct 30, 2013 at 3:26 AM, Thierry Reding
> <thierry.reding@...il.com> wrote:
>> On Wed, Oct 30, 2013 at 01:12:49AM -0500, Rob Herring wrote:
>>> From: Rob Herring <rob.herring@...xeda.com>
>>>
>>> This series adds a couple of boilerplate helpers to match with DT for
>>> initcalls and platform device creation and probe. The goal here is to
>>> remove more platform code out of arch/arm and eventually the machine
>>> descriptors.
>>
>> I fear that this is a step backwards because it makes it easier for
>> people to do the wrong thing. We've been doing the same with interrupt
>> controllers and clocks. With those there's at least the argument that
>> they need to be available really early and therefore cannot use the
>> regular driver model. But for everything else, shouldn't we enforce
>> proper drivers to be written?
>
> You think both are a step backwards or just the initcall one? For
> initcalls, there are things which are not drivers, but just one time
> init.  The example on highbank is highbank_pm_init. In some cases like
> cpuidle, they have been converted to platform drivers, but then we
> have platform code to create devices if we are on the relevant
> platform. There is not really a real device node that exists for some
> of these drivers and we need to create the device rather than the
> device getting created by scanning the buses in the DT.
>
> I think this is less error prone because we've had cases of
> unconditional initcalls which break multi-platform kernels.
>
>> Perhaps if you can point me to some examples I could get more context
>> why and where this would be useful.
>
> I'll push out a WIP branch later which has the above examples and
> removes the machine_desc struct for highbank. This all is more for
> arm64 which doesn't have or want to have a machine_desc.

Here is a branch with example users:

git://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git
highbank-rm-mach-desc

Rob
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