ACPI / hotplug: Introduce user space interface for hotplug profiles

Introduce user space interface for manipulating hotplug profiles
associated with ACPI scan handlers.

The interface consists of sysfs directories under
/sys/firmware/acpi/hotplug/, one for each hotplug profile, containing
an attribute allowing user space to manipulate the enabled field of
the corresponding profile.  Namely, switching the enabled attribute
from '0' to '1' will cause the common hotplug notify handler to be
installed for all ACPI namespace objects representing devices matching
the scan handler associated with the given hotplug profile (and
analogously for the converse switch).

Drivers willing to use the new user space interface should add their
ACPI scan handlers with the help of new funtion
acpi_scan_add_handler_with_hotplug().

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Toshi Kani <toshi.kani@hp.com>
Tested-by: Toshi Kani <toshi.kani@hp.com>

1 files changed, 26 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-firmware-acpi b/Documentation/ABI/testing/sysfs-firmware-acpi
index dd930c8db41f..ce9bee98b43b 100644
--- a/Documentation/ABI/testing/sysfs-firmware-acpi
+++ b/Documentation/ABI/testing/sysfs-firmware-acpi
@@ -18,6 +18,32 @@ Description:
                 yoffset: The number of pixels between the top of the screen
                          and the top edge of the image.
 
+What:           /sys/firmware/acpi/hotplug/
+Date:           February 2013
+Contact:        Rafael J. Wysocki <rafael.j.wysocki@intel.com>
+Description:
+                There are separate hotplug profiles for different classes of
+                devices supported by ACPI, such as containers, memory modules,
+                processors, PCI root bridges etc.  A hotplug profile for a given
+                class of devices is a collection of settings defining the way
+                that class of devices will be handled by the ACPI core hotplug
+                code.  Those profiles are represented in sysfs as subdirectories
+                of /sys/firmware/acpi/hotplug/.
+
+                The following setting is available to user space for each
+                hotplug profile:
+
+                enabled: If set, the ACPI core will handle notifications of
+                        hotplug events associated with the given class of
+                        devices and will allow those devices to be ejected with
+                        the help of the _EJ0 control method.  Unsetting it
+                        effectively disables hotplug for the correspoinding
+                        class of devices.
+
+                The value of the above attribute is an integer number: 1 (set)
+                or 0 (unset).  Attempts to write any other values to it will
+                cause -EINVAL to be returned.
+
 What:           /sys/firmware/acpi/interrupts/
 Date:           February 2008
 Contact:        Len Brown <lenb@kernel.org>