linux-kernel - Re: [ltp] Re: [PATCH v2] Re: Battery class driver.

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Date:	Thu, 02 Nov 2006 12:49:54 -0500
From:	Bill Davidsen <davidsen@....com>
To:	Henrique de Moraes Holschuh <hmh@....eng.br>
CC:	Shem Multinymous <multinymous@...il.com>,
	David Zeuthen <davidz@...hat.com>,
	Richard Hughes <hughsient@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Dan Williams <dcbw@...hat.com>, linux-kernel@...r.kernel.org,
	devel@...top.org, sfr@...b.auug.org.au, len.brown@...el.com,
	benh@...nel.crashing.org,
	linux-thinkpad mailing list <linux-thinkpad@...ux-thinkpad.org>,
	Pavel Machek <pavel@...e.cz>, Jean Delvare <khali@...ux-fr.org>
Subject: Re: [ltp] Re: [PATCH v2] Re: Battery class driver.

Henrique de Moraes Holschuh wrote:
> On Wed, 01 Nov 2006, Greg KH wrote:
>> On Wed, Nov 01, 2006 at 09:53:12PM +0200, Shem Multinymous wrote:
>>> Hi Greg,
>>>
>>> On 11/1/06, Greg KH <greg@...ah.com> wrote:
>>>>> The suggestions so far were:
>>>>> 1. Append units string to the content of such attribute:
>>>>>   /sys/.../capacity_remaining reads "16495 mW".
>>>>> 2. Add a seprate *_units attribute saying what are units for other
>>>>> attribute:
>>>>>   /sys/.../capacity_units gives the units for
>>>>>   /sys/.../capacity_{remaining,last_full,design,min,...}.
>>>>> 3. Append the units to the attribute names:
>>>>>   capacity_{remaining,last_full,design_min,...}:mV.
>>>> No, again, one for power and one for current.  Two different files
>>>> depending on the type of battery present.  That way there is no need to
>>>> worry about unit issues.
>>> I'm missing something. How is that different from option 3 above?
>> No silly ":mV" on the file name.
> 
> As long as that also means no "silly _mV" in the name.  However, if the
> choice is between :mV and _mV, please go with :mV.
> 
>>> BTW, please note that we're talking about a large set of files that
>>> use these units (remaining, last full, design capacity, alarm
>>> thresholds, etc.), and not just a single attribute.
>> Sure, what's wrong with:
>> 	capacity_remaining_power
>> 	capacity_last_full_power
>> 	capacity_design_min_power
>> if you can read that from the battery, and:
>> 	capacity_remaining_current
>> 	capacity_last_full_current
>> 	capacity_design_min_current
>> if you can read that instead.
> 
> Well, "Wh" measures energy and not power, and "Ah" measures electric charge
> and not current, so it would be better to make that:
> 
> capacity_*_energy  (Wh-based)
> 
> and
> 
> capacity_*_charge  (Ah-based)
> 
> Also, should we go with mWh/mAh, or with even smaller units because of the
> tiny battery-driven devices of tomorrow?
> 
Having seen a French consultant with a Windows laptop reporting mJ 
(Joules) I bet that came from the hardware. And given that laptop 
batteries run at (almost) constant voltage, could all of these just be 
converted to mWh for consistency?

-- 
Bill Davidsen <davidsen@....com>
   Obscure bug of 2004: BASH BUFFER OVERFLOW - if bash is being run by a
normal user and is setuid root, with the "vi" line edit mode selected,
and the character set is "big5," an off-by-one errors occurs during
wildcard (glob) expansion.
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