Re: [PATCH] platform: Fix platform device resource linking

From: Pantelis Antoniou
Date: Mon Feb 11 2013 - 12:18:33 EST

Hi Grant,

On Feb 9, 2013, at 12:02 AM, Grant Likely wrote:

> On Fri, 18 Jan 2013 11:05:14 +0200, Pantelis Antoniou <panto@xxxxxxxxxxxxxxxxxxxxxxx> wrote:
>> Hi Greg,
>> On Jan 18, 2013, at 5:00 AM, Greg Kroah-Hartman wrote:
>>> On Thu, Jan 17, 2013 at 07:27:21PM +0200, Pantelis Antoniou wrote:
>>>>>> In a nutshell, we have to exercise the platform device subsystem, in ways
>>>>>> that never happened before, so all sorts of weird bugs that no-one has seen
>>>>>> before.
>>>>> Why do you have to do this? What are you doing that is so different
>>>>> from everyone else? What drivers are you using that trigger this type
>>>>> of thing?
>>>> This is all part of a larger patchset; I guess you weren't directly CCed.
>>>> The name of the patchset is 'Introducing Device Tree Overlays' and is a
>>>> method of changing the live device tree and have the changes reflected to
>>>> the kernel's state.
>>> Ok, no wonder I was confused :)
>>> How about cc:ing me on the next round of these patches, all of the,
>>> which will give me the proper background as to what is going on?
>> Will do. I'm still waiting for some feedback from the DT maintainers, but
>> I will make sure that you will be CCed on the next revision.
>> You can of course take a look at it and comment on the current version too.
>>>>>> In that case, the code path for creating platform devices from DT is
>>>>>> not the same as the one that is used when creating platform device from
>>>>>> a board file.
>>>>> Why not?
>>>> Because while DT creates platform devices, it doesn't use the platform device
>>>> methods to do so, rather than builds the platform device itself. This is
>>>> something that was overlooked.
>>> Can't this be fixed? What does the platform device core need to do to
>>> resolve this?
>> Hmm, due to historical reasons the two ways of creating platform devices
>> have diverged. The core of the issue is that while OF creates platform devices
>> it does so in it's own way.
> It's actually the other way around. The DT code path used to be a
> completely separate of_platform_bus_type that didn't share any code with
> platform_bus_type. So in fact, the code patches have converged instead
> of diverged.
> When I merged the paths there were some breakages that prevented me from
> using platform_device_add() directly. Most of those are now gone and
> I've got a patch in my tree which makes the OF code use
> platform_device_add(). That makes this patch series unnecessary. The
> patch is currently in linux-next. Assuming I don't run into any major
> problems it will be merged in v3.9

I'm fine with this, as long as nothing breaks. I'll wait until it lands in
mainline to test it.

>> The problem with doing anything like this would be that a whole bunch of
>> devices/arches depend on DT, and if anything breaks there will be a lot of
>> angry people with pitchforks after the culprit.
> Pitchforks? pish. It's the torches that are dangerous.

Fire bad. Got it.

> g.

What about the other (more substantial) patches that are in limbo? Any word
on them?


-- Pantelis

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