Hi Greg,
On 10/31/06, Greg KH <[email protected]> wrote:
> On 10/28/06, David Zeuthen <[email protected]> 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.
It sure is easier, but we're discussinng the case where units change
in runtime; what do we document then? Plug in a different battery and
you get reports in mA and mAh insted of mW and mWh.
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.
Shem
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