RPM_SUSPENDED, which means that each device is initially regarded by the
PM core as 'suspended', regardless of its real hardware status
+ `enum rpm_status last_status;`
+ - the last runtime PM status of the device captured before disabling runtime
+ PM for it (invalid initially and when disable_depth is 0)
+
`unsigned int runtime_auto;`
- if set, indicates that the user space has allowed the device driver to
power manage the device at run time via the /sys/devices/.../power/control
`int pm_runtime_resume(struct device *dev);`
- execute the subsystem-level resume callback for the device; returns 0 on
- success, 1 if the device's runtime PM status was already 'active' or
- error code on failure, where -EAGAIN means it may be safe to attempt to
- resume the device again in future, but 'power.runtime_error' should be
- checked additionally, and -EACCES means that 'power.disable_depth' is
+ success, 1 if the device's runtime PM status is already 'active' (also if
+ 'power.disable_depth' is nonzero, but the status was 'active' when it was
+ changing from 0 to 1) or error code on failure, where -EAGAIN means it may
+ be safe to attempt to resume the device again in future, but
+ 'power.runtime_error' should be checked additionally, and -EACCES means
+ that the callback could not be run, because 'power.disable_depth' was
different from 0
`int pm_runtime_resume_and_get(struct device *dev);`