From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jani Nikula <jani.nikula@linux.intel.com>
Subject: Re: [PATCH v4 1/4] backlight: introduce backlight_device_registered
Date: Thu, 10 Oct 2013 07:29:53 +0300
Message-ID: <878uy1694u.fsf@intel.com>
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To: Aaron Lu <aaron.lu@intel.com>, "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: linux-acpi@vger.kernel.org, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Daniel Vetter <daniel@ffwll.ch>, Matthew Garrett <matthew.garrett@nebula.com>, Seth Forshee <seth.forshee@canonical.com>, Lee Chun-Yi <joeyli.kernel@gmail.com>, Richard Purdie <rpurdie@rpsys.net>, Igor Gnatenko <i.gnatenko.brain@gmail.com>, Yves-Alexis Perez <corsac@debian.org>, Felipe Contreras <felipe.contreras@gmail.com>, Ben Jencks <ben@bjencks.net>, Steven Newbury <steve@snewbury.org.uk>, James Hogan <james@albanarts.com>, Kamal Mostafa <kamal@canonical.com>, Joerg Platte <jplatte@naasa.net>, Kalle Valo <kvalo@adurom.com>, Martin Steigerwald <Martin@lichtvoll.de>, =?utf-8?Q?J=C3=B6rg?= Otte <jrg.otte@gmail.com>, Mike Galbraith <bitbucket@online.de>, platform-driver-x86@vger.kernel.org, Mika Westerberg <mika.westerberg@linux.intel.com>
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On Thu, 10 Oct 2013, Aaron Lu <aaron.lu@intel.com> wrote:
> On 10/10/2013 08:25 AM, Rafael J. Wysocki wrote:
>> On Tuesday, October 08, 2013 02:39:58 PM Aaron Lu wrote:
>>> +bool backlight_device_registered(enum backlight_type type)
>>> +{
>>> +	bool found = false;
>>> +	struct backlight_device *bd;
>>> +
>>> +	mutex_lock(&bd_list_mutex);
>>> +	list_for_each_entry(bd, &bd_list_head, entry) {
>>> +		if (bd->props.type == type) {
>>> +			found = true;
>>> +			break;
>>> +		}
>>> +	}
>> 
>> Isn't it useful to be able to register more than one backlight device of the
>> same type sometimes?
>
> I think so for some kind of computers. OTOH, the above function should
> be enough for the problem we are solving here, if someday we need to
> differentiate, we can enhance the code then.

Since both Baytrail and Haswell already have two backlight PWMs, this
may be needed sooner than you think. But we shouldn't let that block
fixing the more urgent issue we have now. So I'm fine with this. It
doesn't prevent one from registering more than one device of the same
type anyway.

BR,
Jani.



-- 
Jani Nikula, Intel Open Source Technology Center