linux-kernel - Re: [RFC PATCH 0/3] introduce: Multistate Switch Class

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Date:	Tue, 29 Nov 2011 17:18:14 +0900
From:	MyungJoo Ham <myungjoo.ham@...il.com>
To:	Greg KH <gregkh@...e.de>
Cc:	linux-kernel@...r.kernel.org, Mike Lockwood <lockwood@...roid.com>,
	Arve Hjønnevåg <arve@...roid.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Donggeun Kim <dg77.kim@...sung.com>,
	Arnd Bergmann <arnd@...db.de>
Subject: Re: [RFC PATCH 0/3] introduce: Multistate Switch Class

On Sun, Nov 27, 2011 at 12:32 AM, Greg KH <gregkh@...e.de> wrote:
> On Thu, Nov 24, 2011 at 11:03:53AM +0900, MyungJoo Ham wrote:
>> For switch ports, which may have different types of cables
>> (USB, TA, HDMI, Analog A/V, and others), we often have seperated device
>> drivers that detect the state changes at the port and device drivers that
>> do something according to the state changes.
>>
>> For example, when MAX8997-MUIC detects a Charger cable insertion, another
>> device driver (such as MAX8903 charger, MAX8997 charger, Charger Manager,
>> or board file) needs to set charger current limit accordingly and when
>> MAX8997-MUIC detects a HDMI cable insertion, multimedia device drivers
>> need to do some operations accordingly.
>>
>> This patchset supports the usage of notifier for passing such information
>> between device drivers.
>>
>> Another issue is that at a single switch port, there might be multiple
>> and heterogeneous cables attached at the same time. Besides, the state
>> (Attached or Detached) of each cable may alter independently.
>>
>> In order to address such issues, Android kernel's "Switch" class seems to
>> be a good basis and we have implemented "Multistate Switch Class" based on
>> it. The "Switch" class code of Android kernel is GPL as well.
>
> I have the same objections to this patchset that Arnd does, as well as
> the fact that there is no documentation of this new userspace api.
>
> Please include a Documentation/ABI file that describes exactly what you
> are adding here, and how this is to be used, so that we can properly
> review it next time, if you end up sticking with this "new" interface
> proposal.
>
> thanks,
>
> greg k-h
>

Although it only has read-only "state", "name" sysfs entries, sure,
I'll add them at Documentation/ABI with the next iteration.


Cheers!
MyungJoo
-- 
MyungJoo Ham, Ph.D.
Mobile Software Platform Lab, DMC Business, Samsung Electronics
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