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 08:23:02 +0300
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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 12:29 PM, Jani Nikula wrote:
>> 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
>
> Do we need to differentiate which backlight PWM is registered to decide
> if ACPI video backlight interface should be skipped? My understanding is
> no.

That's correct. If things change, we can fix it then.

Jani.


>
> Thanks,
> Aaron
>
>> 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