This patch introduces acpi_handle_<level>(), where <level> is
a kernel message level such as err/warn/info, to support improved
logging messages for ACPI, esp. hot-plug operations.
acpi_handle_<level>() appends "ACPI" prefix and ACPI object path
to the messages.  This improves diagnosis of hotplug operations
since an error message in a log file identifies an object that
caused an issue.  This interface acquires the global namespace
mutex to obtain an object path.  In interrupt context, it shows
the object path as <n/a>.

acpi_handle_<level>() takes acpi_handle as an argument, which is
passed to ACPI hotplug notify handlers from the ACPICA.  Therefore,
it is always available unlike other kernel objects, such as device.

For example:
  acpi_handle_err(handle, "Device don't exist, dropping EJECT\n");
logs an error message like this at KERN_ERR.
  ACPI: \_SB_.SCK4.CPU4: Device don't exist, dropping EJECT

ACPI hot-plug drivers can use acpi_handle_<level>() when they need
to identify a target ACPI object path in their messages, such as
error cases.  The usage model is similar to dev_<level>().
acpi_handle_<level>() can be used when a device is not created or
is invalid during hot-plug operations.  ACPI object path is also
consistent on the platform, unlike device name that gets incremented
over hotplug operations.

ACPI drivers should use dev_<level>() when a device object is valid.
Device name provides more user friendly information, and avoids
acquiring the global ACPI namespace mutex.  ACPI drivers also
continue to use pr_<level>() when they do not need to specify device
information, such as boot-up messages.

Note: ACPI_[WARNING|INFO|ERROR]() are intended for the ACPICA and
are not associated with the kernel message level.
Signed-off-by: Toshi Kani <toshi.kani@hp.com>
Tested-by: Vijay Mohan Pandarathil <vijaymohan.pandarathil@hp.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>