Miguel Ojeda пишет:
On Mon, Oct 5, 2009 at 12:38 AM, Alexey Starikovskiy
<astarikovskiy@xxxxxxx> wrote:
Miguel Ojeda пишет:
On Sun, Oct 4, 2009 at 11:36 PM, Alexey Starikovskiy
<astarikovskiy@xxxxxxx> wrote:
Hi Rafael,
This is not my rule, it was/is the rule of power device class. If you do
not
agree to it, please change
appropriate documentation.
Oh, I did not know that. Thank you for pointing it out. I think you
are refering to:
158Q: Suppose, my battery monitoring chip/firmware does not provides
capacity
159 in percents, but provides charge_{now,full,empty}. Should I
calculate
160 percentage capacity manually, inside the driver, and register
CAPACITY
161 attribute? The same question about time_to_empty/time_to_full.
162A: Most likely, no. This class is designed to export properties which
are
163 directly measurable by the specific hardware available.
164
165 Inferring not available properties using some heuristics or
mathematical
166 model is not subject of work for a battery driver. Such
functionality
167 should be factored out, and in fact, apm_power, the driver to serve
168 legacy APM API on top of power supply class, uses a simple
heuristic of
169 approximating remaining battery capacity based on its charge,
current,
170 voltage and so on. But full-fledged battery model is likely not
subject
171 for kernel at all, as it would require floating point calculation
to deal
172 with things like differential equations and Kalman filters. This is
173 better be handled by batteryd/libbattery, yet to be written.
We are not calculating anything new just by the pleasure of doing it,
we are correcting a wrong value provided by the hardware.
You are guessing that normal battery can not jump charge value, and on this
assumption you
cap charge_now with last full_charge. Immediate problem is that full_charge
is not fixed value,
this is why it is separated from design_full_charge.
During battery life full_charge may go down and up, depending on outside
temperature, battery discharge (full or partial).
I've seen batteries on some new machines reporting full charge of more than
design charge.
Obviously, your patch will fail in some of the above situations.
I don't see why. The patch compares against full_charge every time
(which is updated as you say), not against design_full_charge.
1. full_charge > design_full_charge => OK, design_full_charge is not
involved in the min() operation.
2. full_charge goes down => If charge_now > full_charge then hardware
is wrong and we should read full_charge. OK.
3. full_charge goes up => Same.
full_charge_capacity is the value of last full charge. It will be updated to
current full charge, when the charging is complete. It may end up lower or greater than
previous value.
Comparing current charge with the last full charge may correctly give you >100%.
Now we have a decision to make -- do we update full charge to be greater than charge now,
or do we update charge now to be lower than full charge.
So, maybe the battery works as you suggested; still, the kernel should
provide a common meaning to its interfaces. If some batteries report
full_charge when in "charged" state and others report
design_full_charge, then the kernel should convert all of them into
one unique convention, or there is no sane way to write userspace
applications.
I still want to receive raw data from driver, and have 1 level of interpreters.
As I understand, there is HAL, which may do interpretations for you and keep it in single location.
Regards,
Alex.
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