Re: [PATCH v4 3/3] PM / DEVFREQ: add sysfs interface (including user tickling)

From: MyungJoo Ham <myungjoo.ham@samsung.com>
To: Pavel Machek <pavel@ucw.cz>
Cc: Len Brown <len.brown@intel.com>,
	Greg Kroah-Hartman <gregkh@suse.de>,
	Kyungmin Park <kyungmin.park@samsung.com>,
	linux-pm@lists.linux-foundation.org,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH v4 3/3] PM / DEVFREQ: add sysfs interface (including user tickling)
Date: Tue, 19 Jul 2011 11:14:56 +0900	[thread overview]
Message-ID: <CAJ0PZbTYNAssXYiOq8zjU9uv-zu-tK1msiMyYz0F0p_DkENMQQ@mail.gmail.com> (raw)
In-Reply-To: <20110609171157.GA3877@ucw.cz>

On Fri, Jun 10, 2011 at 2:11 AM, Pavel Machek <pavel@ucw.cz> wrote:
> Hi!
>
>> +What:                /sys/devices/.../power/devfreq_polling_interval
>> +Date:                July 2011
>> +Contact:     MyungJoo Ham <myungjoo.ham@samsung.com>
>> +Description:
>> +             The /sys/devices/.../power/devfreq_polling_interval shows the
>> +             requested polling interval of the corresponding device.
>
> AFAICT, polling only makes sense for one governor; and I guess more
> governor parameters will be needed in future. Should polling interval
> be governor-specific?

struct devfreq_governor {
        char name[DEVFREQ_NAME_LEN];
        void *data; /* private data for get_target_freq */
        int (*get_target_freq)(struct devfreq *this, unsigned long *freq);
};

The "data" entry in struct devfreq_governor is meant to be the
parameters as well as internal governor data in the future; the
current three example governors do not need it anyway.

Unlike CPUFREQ, we have many heterogeneous devices to support with
DEVFREQ. Thus, a specific device may need a governor with its own
unique design and supply such a governor (not defined as those
examples in devfreq.c) with devfreq_add_device.

And, yes. Among those three examples, only "simple-ondemand" is
required to use polling interval.

However, any drivers may add its own governors with polling and
tickling requires polling interval regardless of the governor used.

Therefore, I think polling interval is not governor specific in devfreq.

Thank you.
- MyungJoo

> --
> (english) http://www.livejournal.com/~pavelmachek
> (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
>

-- 
MyungJoo Ham (함명주), Ph.D.
Mobile Software Platform Lab,
Digital Media and Communications (DMC) Business
Samsung Electronics
cell: 82-10-6714-2858
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