acpi_powerres: `acpi_pwr_get_state` and getting initial D-state for deviceHEADmain

Add `acpi_pwr_get_state` as a prerequisite to LPI (low-power idle)
states. Since these states define minimum D-state constraints on other
devices to be able to enter them, it will be necessary to use this
function to check them before attempting to do so.

Aside from that, this function is used to get the initial D-state of a
power consumer when registering it (previously the `ac_state` value
would be set to `ACPI_STATE_UNKNOWN`). It uses the `_PSC` method if
available (older devices), or infers the D-state through the `_PRx`
objects (cached in `ac_prx`) with `acpi_pwr_infer_state` if not.

`acpi_pwr_switch_consumer` now uses this to verify that the D-state of
a power consumer was switched correctly.

Reviewed by:	imp, markj, jrm (mentor)
Approved by:	markj, jrm (mentor)
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D48386

0 files changed, 0 insertions, 0 deletions