Some PCI devices provide power management capabilities in addition to those provided by the PCI Power Management Specification. The pci_report_pmcap(9f)
function reports those Power Management capabilities of the PCI device to the framework. Framework supports dynamic changing of the capability by allowing pci_report_pmcap(9f) to be called multiple times. Following are the
supported capabilities as indicated by the cap:
PCI_PM_IDLESPEED -- The PCI_PM_IDLESPEED value indicates the lowest PCI clock speed that a device can tolerate when idle, and is applicable only to 33 MHz PCI bus. arg represents the lowest possible idle speed in KHz (1 KHz is 1000 Hz).
The integer value representing the speed should be cast to (void *) before passing as arg to pci_report_pmcap(9f).
The special values of arg are:
-
PCI_PM_IDLESPEED_ANY
- The device can tolerate any idle clock speed.
-
PCI_PM_IDLESPEED_NONE
- The device cannot tolerate slowing down of PCI clock even when idle.
If the driver doesn't make this call, PCI_PM_IDLESPEED_NONE is assumed. In this case, one offending device can keep the entire bus from being power managed.
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