linux-kernel - Re: [linux-pm] [RFC PATCH] thermal: Add support to report cooling statistics achieved by cooling devices

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Date:	Tue, 7 Feb 2012 10:26:02 -0800
From:	Amit Kachhap <amit.kachhap@...aro.org>
To:	Greg KH <greg@...ah.com>
Cc:	Pavel Machek <pavel@....cz>, linux-pm@...ts.linux-foundation.org,
	linaro-dev@...ts.linaro.org, patches@...aro.org,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	rob.lee@...aro.org
Subject: Re: [linux-pm] [RFC PATCH] thermal: Add support to report cooling
 statistics achieved by cooling devices

On 6 February 2012 16:18, Greg KH <greg@...ah.com> wrote:
> On Mon, Feb 06, 2012 at 03:16:17PM -0800, Amit Kachhap wrote:
>> On 6 February 2012 09:03, Greg KH <greg@...ah.com> wrote:
>> > On Mon, Feb 06, 2012 at 05:56:58PM +0100, Pavel Machek wrote:
>> >> Hi!
>> >>
>> >> > Add a sysfs node code to report effective cooling of all cooling devices
>> >> > attached to each trip points of a thermal zone. The cooling data reported
>> >> > will be absolute if the higher temperature trip points are arranged first
>> >> > otherwise the cooling stats is the cumulative effect of the earlier
>> >> > invoked cooling handlers.
>> >> >
>> >> > The basic assumption is that cooling devices will bring down the temperature
>> >> > in a symmetric manner and those statistics can be stored back and used for
>> >> > further tuning of the system.
>> >>
>> >> /sys fs should be one-value-per-file, talk to gregkh.
>> >
>> > That's correct.
>> >
>> > Why not use debugfs for this instead?
>> >
>> > thanks,
>> >
>> > greg k-h
>>
>> Thanks Greg/Pavel for looking into the patch.
>> Basically I checked the places where single sysfs entry is showing
>> more then 1 output. And
>> 1) /sys/devices/system/cpu/cpu0/cpufreq/stats/time_in_state
>> 2) /sys/devices/system/cpu/cpu0/cpufreq/stats/trans_table
>> are the places where the output is more than 1 value.
>
> Yes, those are two known-bad files, whose files will change soon and
> move to debugfs.
>
> Just because you found 2, instead of the thousands of other properly
> formatted files, does not mean you are allowed to create something like
> this.
>
>> Anyway I can enclose this sysfs inside CONFIG_THERMAL_COOLING_STATS macro.
>
> No, you can not create it at all in sysfs, if you really need such a
> large single file, use debugfs instead, that is what it is there for.
>
> Again, one-value-per-file is the sysfs rule, and has been for a decade
> now, please don't think this is a new thing.
>
> greg k-h

Ok I will follow one-value-per-file rule for sysfs file. Thanks
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