Re: [PATCH v2] Re: Battery class driver.

On Wed, Nov 01, 2006 at 09:53:12PM +0200, Shem Multinymous wrote:
Hi Greg,

On 11/1/06, Greg KH <greg@xxxxxxxxx> 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.

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.

This particular alternative indeed seems cleanest for the kernel side.
The drawback is that someone in userspace who doesn't care about units
but just wants to show a status report or compute the amount of
remaining fooergy divided by the amount of a fooergy when fully
charged, like your typical battery applet, will need to parse
filenames (or try out a fixed and possibly partial list) to find out
which attribute files contain the numbers.

If the file isn't there, they the attribute isn't present. It doesn't
get easier than that.

And of course user apps will have to change, but only once. And then
they will work with all types of batterys, unlike today.

thanks,

greg k-h
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