linux-kernel - Re: [PATCH 1/1] Introduce Intel RAPL cooling device driver

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Message-ID: <20130402165340.61b7da02@chromoly>
Date:	Tue, 2 Apr 2013 16:53:40 -0700
From:	Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Platform Driver <platform-driver-x86@...r.kernel.org>,
	Matthew Garrett <matthew.garrett@...ula.com>,
	Zhang Rui <rui.zhang@...el.com>,
	Rafael Wysocki <rafael.j.wysocki@...el.com>,
	Len Brown <len.brown@...el.com>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	Arjan van de Ven <arjan@...ux.intel.com>
Subject: Re: [PATCH 1/1] Introduce Intel RAPL cooling device driver

On Tue, 2 Apr 2013 16:00:42 -0700
Greg KH <gregkh@...uxfoundation.org> wrote:

> And, one final complaint, never use "raw" kobjects, for loads of good
> reasons, not the least being you just prevented userspace from seeing
> what is happening with your devices.  Use the driver model, that's
> what it is there for, if you need "sub children", or subdirectories.
I chose to use to kobjects for the reason that userspace can see the
device linking more clearly.
Let me try to paraphrase, I have two options:
1. if I use the platform device model instead of raw kobjects, I would
have one platform device for each rapl domain. Then link individual
platform device with the generic thermal layer sysfs.

2. In the current patch, I have one platform driver, then expose per
domain kobject that can be linked to the generic thermal layer. Common
attributes of all domains are grouped under the kset. 

I did consider both options. I thought using #2 option is better since
it allow user to discover the topologies easier by following the
sysfs link. If i use use #1, it would be hard to expose the common
attributes and more code too. Perhpas I misread
Documentation/kobjects.txt which i thought kobject/kset are perfect for
presenting situation like this.

-- 
Thanks,

Jacob
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