Re: [PATCH v3 2/3] acpi: dptf_power: Add DPTF power participant

[Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>]

On Fri, 2016-06-24 at 02:26 +0200, Rafael J. Wysocki wrote:
> > > > 
> On Fri, Jun 24, 2016 at 1:19 AM, Srinivas Pandruvada
> <srinivas.pandruvada@linux.intel.com> wrote:
> > On Fri, 2016-06-24 at 00:31 +0200, Rafael J. Wysocki wrote:
> > > On Thu, Jun 23, 2016 at 11:42 PM, Srinivas Pandruvada
> > > <srinivas.pandruvada@linux.intel.com> wrote:
[...]

> I think what you need is that if acpi_battery is bound to at least
> one
> device, you don't want to bind dptf_power to anything.  Conversely,
> if
> dptf_power has been bound to at least one device, you don't want to
> bind acpi_battery to anything.
> 
> That may be achieved with a lock and two counters, one (A)
> incremented
> only by acpi_battery and the other (B) incremented only by dptf_power
> and such that you can't increment A if B is different from 0 and you
> can't increment B if A is different from 0.  Of course, each driver
> would need to specify which counter it wants to use (A or B), so that
> would take an additional argument to acpi_battery_common_add() and an
> additional field in struct acpi_battery (for the remove operation).
> 
> With that, I think it should only be possible to build both
> acpi_battery and dptf_power if they are both modules.  IOW,
> DPTF_POWER
> should depend on (!ACPI_BATTERY || ACPI_BATTERY=m) or similar.  And
> if
> they are both modules, let user space manage that.
> 
> And the waiting itself doesn't add any value then IMO.
Yes. I think the best solution is not to let define DPTF_POWER when the
ACPI_BATTERY is defined same as my first version of the patch or let
both add as there is no harm as they will show same levels. The reason
is:
We have some devices with two ACPI_BATTERIES (primary and
secondary/backup) and they must be presented as two power supply
devices to user space. In those devices DPTF_POWER may be equivalent to
only one of the ACPI_BATTERY (Will point to same battery for Battery
levels). So we can't simply refuse to add ACPI_BATTERY device addition
because DPTF_POWER device is registered before.

Thanks,
Srinivas





> Thanks,
> Rafael
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