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

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Date:	Mon, 30 Oct 2006 23:49:46 -0800
From:	Greg KH <greg@...ah.com>
To:	Shem Multinymous <multinymous@...il.com>
Cc:	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: [PATCH v2] Re: Battery class driver.

On Sat, Oct 28, 2006 at 08:12:41PM +0200, Shem Multinymous wrote:
> Hi David,
> 
> On 10/28/06, David Zeuthen <davidz@...hat.com> wrote:
> >What about just prepending the unit to the 'threshold' file? Then user
> >space can expect the contents of said file to be of the form "%d %s". I
> >don't think that violates the "only one value per file" sysfs mantra.
> 
> The tp_smapi battery driver did just this  ("16495 mW"). But I dropped
> it in a recent version when Pavel pointed out the rest of sysfs, hwmon
> included, uses undecorated integers.
> Consistency aside, it seems reasonable and convenient. You have to
> decree that writes to the attributes (where relevant) don't include
> the units, of course, so no one will expect the kernel to parse that.
> 
> There's an issue here if a drunk driver decides to specify (say)
> capacity_remaining in mWh and capacity_last_full in mAa, which will
> confuse anyone comparing those attributest. So don't do that.
> 
> Jean, what's your opinion on letting hwmon-ish attributes specify
> units as "%d %s" where these are hardware-dependent?

No, the sysfs files should just always keep the same units as
documented.  It's easier all around that way.

thanks,

greg k-h
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