From: Kevin Hilman <khilman@deeprootsystems•com>
To: Grant Likely <grant.likely@secretlab•ca>
Cc: "Moffett\, Kyle D" <Kyle.D.Moffett@boeing•com>,
Patrick Pannuto <ppannuto@codeaurora•org>,
"linux-kernel\@vger.kernel.org" <linux-kernel@vger•kernel.org>,
"linux-arm-msm\@vger.kernel.org" <linux-arm-msm@vger•kernel.org>,
"magnus.damm\@gmail.com" <magnus.damm@gmail•com>,
"gregkh\@suse.de" <gregkh@suse•de>,
Paul Mundt <lethal@linux-sh•org>,
Magnus Damm <damm@opensource•se>,
"Rafael J. Wysocki" <rjw@sisk•pl>,
Eric Miao <eric.y.miao@gmail•com>, Dmitry Torokhov <dtor@mail•ru>,
"netdev\@vger.kernel.org" <netdev@vger•kernel.org>,
Kyle D Moffett <kyle@moffetthome•net>
Subject: Re: [PATCH 2/2] platform: Facilitate the creation of pseudo-platform buses
Date: Fri, 20 Aug 2010 17:10:00 -0700 [thread overview]
Message-ID: <87y6c03jxj.fsf@deeprootsystems.com> (raw)
In-Reply-To: <AANLkTine=VLLm4+ReKeMKBdbV1JsunNagwKxGMDhEe8e@mail.gmail.com> (Grant Likely's message of "Fri, 20 Aug 2010 14:08:49 -0600")
Grant Likely <grant.likely@secretlab•ca> writes:
[...]
>>>
>>> My fears on this point may very well be unfounded. This isn't the
>>> hill I'm going to die on either. Show me an implementation of driver
>>> sharing that is clean and prove me wrong! :-)
>>
>> IMHO, simply overriding the few dev_pm_ops methods was the cleanest and
>> simplest.
>>
>> Since we seem to be in agreement now that the a new bus may not the
>> right abstraction for this (since we want it to be completely
>> transparent to the drivers), I'll go back to the original design. No new
>> bus types, keep the platform_bus as is, but simply override the few
>> dev_pm_ops methods I care about. This is what is done on SH,
>> SH-Mobile[1] and my original version for OMAP that started this
>> conversation.
>>
>> Yes, the weak-symbol method of overriding is not scalable, but that's a
>> separate issue from whether or not to create a new bus. I have a
>> proposed fix for the weak which I'll post shortly.
>
> Okay.
>
> One constraint remains though: If you can override the dev_pm_ops on
> a per-device or per-device-parent basis, then you've got my support.
hmm, a new requirement?, and one that would require some significant
changes to the driver model.
Currently, dev_pm_ops for a bus applies globally to *all* devices on
that bus (or class or type) and changing that would require changing the
platform_bus code to start having per-device (or per-parent-device)
checks.
> If the override (even when fixed to work at runtime) applies to every
> device on the platform_bus_type, then I'll nack it.
/me can't help but wonder why the OMAP implementation is getting all the
negative attention while the other identical implementations are already
upstream.
> My concern here is that the SoC or platform support code doesn't get
> to "own" the platform_bus_type.
Well, I'm not proposing that here. This "feature" already exists in
mainline (albeit using the less-than-optimal weak symbol approach.) All
I'm proposing is fixing it to make it multi-arch friendly.
If you think this behavior should be changed to non global, that should
be done a separate series since it is not directly related to runtime PM
support for a given platform, IMO.
> Other drivers/code can register their own set of
> platform_devices, which may also need to perform their own dev_pm_ops
> override.
IMHO, we should deal with such hypothetical, future problems *if* they
arise down the road.
> If the override is global to the platform_bus_type, then the model
> will not scale.
It will not scale any more (or less) than the current functionality of
the driver model which handles this globally. Again, if scalabilty
becomes a problem down the road, lets fix it then.
Kevin
next prev parent reply other threads:[~2010-08-21 0:10 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1281484174-32174-1-git-send-email-ppannuto@codeaurora.org>
2010-08-10 23:49 ` [PATCH 2/2] platform: Facilitate the creation of pseudo-platform buses Patrick Pannuto
2010-08-13 1:13 ` Patrick Pannuto
2010-08-14 21:04 ` Greg KH
2010-08-13 22:05 ` Grant Likely
2010-08-16 18:47 ` Patrick Pannuto
2010-08-16 20:25 ` Grant Likely
2010-08-16 23:58 ` Michał Mirosław
[not found] ` <3F978429-F916-42E5-8B36-6AC02DAC8CA2@boeing.com>
2010-08-16 6:43 ` Grant Likely
2010-08-19 19:20 ` Kevin Hilman
2010-08-19 22:22 ` Grant Likely
2010-08-20 18:51 ` Kevin Hilman
2010-08-20 20:08 ` Grant Likely
2010-08-21 0:10 ` Kevin Hilman [this message]
2010-08-21 7:10 ` Grant Likely
2010-08-23 14:53 ` Kevin Hilman
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