linux-kernel - Re: [PATCH v5 4/5] Extcon: support mutually exclusive relation between cables.

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Date:	Mon, 27 Feb 2012 15:47:32 +0900
From:	MyungJoo Ham <myungjoo.ham@...il.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	linux-kernel@...r.kernel.org, NeilBrown <neilb@...e.de>,
	Randy Dunlap <rdunlap@...otime.net>,
	Mike Lockwood <lockwood@...roid.com>,
	Arve Hjønnevag <arve@...roid.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Donggeun Kim <dg77.kim@...sung.com>,
	gregkh@...uxfoundation.org,
	Linus Walleij <linus.walleij@...aro.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Morten CHRISTIANSEN <morten.christiansen@...ricsson.com>,
	John Stultz <john.stultz@...aro.org>,
	Joerg Roedel <joerg.roedel@....com>
Subject: Re: [PATCH v5 4/5] Extcon: support mutually exclusive relation
 between cables.

On Fri, Feb 24, 2012 at 9:53 PM, Arnd Bergmann <arnd@...db.de> wrote:
> On Friday 24 February 2012, MyungJoo Ham wrote:
>> Ok, here goes an example how it would look like in the next revision of Extcon.
>> I think this addresses your comments on multistate-support patch (3/5)
>>
>> /sys/class/extcon/max8997-muic.0/
>>         name: "max8997-muic.0"
>>         state: 0x00000009                   /* RW. 0xblahblah format
>> for both read and write */
>>         mutually_exclusive/
>>                 rule.0: 0x3
>>                 rule.1: 0x5
>>                 rule.2: 0xC

==> I'll simply add 0x3, 0x5, 0xc as the filenames insteadof rule.0 .. 2.

>>         cable.0/
>>                 name: "VGA"
>>                 state: 1            /* RW: 0 or 1 */
>>                 mutually_exclusive/
>>                         cable.1
>>                         cable.2

==> Removing this subdirectory, "mutually_exclusive"

>>         cable.1/
>>           ...
>>
>>
>> How about this?
>>
>
> I would leave out the global mutually_exclusive/ directory because that
> is redundant and I see no benefit in it. Having the redundant "state"
> files is probably a good idea because the global one lets you make
> atomic changes of multiple cables and the other are very convenient.
>
> What kind of object is /sys/class/extcon/max8997-muic.0/cable.0/mutually_exclusive?
> Is that a file with two lines, a directory with two empty files or
> a directory with symlinks to the other directories?

I meant it to be a directory containing attributes (w/o show/store
callbacks) with names of exclusive cables.

However, because we cannot make 2nd-subdirectories under a kobject (I
didn't know this until some hours ago), it appears that I need to
avoid this approach until it is allowed to do so.

Because the redundant information is in the global mutually_exclusive
directory, I'll skip this one (mutually_exclusive subdirectory under
cable.x subdirectory).


>
>        Arnd





Cheers!
MyungJoo.
-- 
MyungJoo Ham, Ph.D.
System S/W Lab, S/W Center, Samsung Electronics
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