Re: envstat wrong: who's at fault?

[Jukka Ruohonen <jruohonen%iki.fi@localhost>]

On Mon, Jul 26, 2010 at 02:40:18AM -0400, der Mouse wrote:
> The problem is that the charge is decreasing significantly faster than
> the discharge rate indicates.  If the charge figures are accurate, the
> discharge rate here is more like 18-19 W (eg, consider the third and
> fourth data points above: (46.74 Wh - 46.41 Wh) / (1/60 h) = 19.8 W).

All values reported by envstat(8) come directly from ACPI. I am not sure
what kind of chip lies beneath, but these inaccuracies are likely a hardware
rather than a software problem.  Also: it is not guaranteed that the
firmware would not manipulate the readings.

> The current software is 4.0.1, and one of the reasons I'm asking
> whether this could be software is that that affects how plausible it is
> that newer code might fix it.

You will find the readings to be identical in HEAD and in 4.0.1 (or earlier).

You could consider some kind of normalization by using the envsys(4) API,
but I am afraid that there is not much we can do about the actual readings.

- Jukka.