Merge branch 'for-2.6.31' of git://git.linux-nfs.org/projects/trondmy/nfs-2.6

[pandora-kernel.git] / Documentation / rfkill.txt

diff --git a/Documentation/rfkill.txt b/Documentation/rfkill.txt
index 1b74b5f..b486050 100644 (file)
--- a/Documentation/rfkill.txt
+++ b/Documentation/rfkill.txt
@@ -3,9 +3,8 @@ rfkill - RF kill switch support
 
 1. Introduction
 2. Implementation details
 
 1. Introduction
 2. Implementation details

-3. Kernel driver guidelines
-4. Kernel API
-5. Userspace support
+3. Kernel API
+4. Userspace support

 
 
 1. Introduction
 
 
 1. Introduction


@@ -19,82 +18,62 @@ disable all transmitters of a certain type (or all). This is intended for
 situations where transmitters need to be turned off, for example on
 aircraft.
 
 situations where transmitters need to be turned off, for example on
 aircraft.
 

+The rfkill subsystem has a concept of "hard" and "soft" block, which
+differ little in their meaning (block == transmitters off) but rather in
+whether they can be changed or not:
+ - hard block: read-only radio block that cannot be overriden by software
+ - soft block: writable radio block (need not be readable) that is set by
+               the system software.

 
 
 2. Implementation details
 
 
 
 2. Implementation details
 

-The rfkill subsystem is composed of various components: the rfkill class, the
-rfkill-input module (an input layer handler), and some specific input layer
-events.
-
-The rfkill class is provided for kernel drivers to register their radio
-transmitter with the kernel, provide methods for turning it on and off and,
-optionally, letting the system know about hardware-disabled states that may
-be implemented on the device. This code is enabled with the CONFIG_RFKILL
-Kconfig option, which drivers can "select".
-
-The rfkill class code also notifies userspace of state changes, this is
-achieved via uevents. It also provides some sysfs files for userspace to
-check the status of radio transmitters. See the "Userspace support" section
-below.
+The rfkill subsystem is composed of three main components:
+ * the rfkill core,
+ * the deprecated rfkill-input module (an input layer handler, being
+   replaced by userspace policy code) and
+ * the rfkill drivers.

 
 

+The rfkill core provides API for kernel drivers to register their radio
+transmitter with the kernel, methods for turning it on and off and, letting
+the system know about hardware-disabled states that may be implemented on
+the device.

 
 

-The rfkill-input code implements a basic response to rfkill buttons -- it
-implements turning on/off all devices of a certain class (or all).
+The rfkill core code also notifies userspace of state changes, and provides
+ways for userspace to query the current states. See the "Userspace support"
+section below.

 
 When the device is hard-blocked (either by a call to rfkill_set_hw_state()
 
 When the device is hard-blocked (either by a call to rfkill_set_hw_state()

-or from query_hw_block) set_block() will be invoked but drivers can well
-ignore the method call since they can use the return value of the function
-rfkill_set_hw_state() to sync the software state instead of keeping track
-of calls to set_block().
-
-
-The entire functionality is spread over more than one subsystem:
-
- * The kernel input layer generates KEY_WWAN, KEY_WLAN etc. and
-   SW_RFKILL_ALL -- when the user presses a button. Drivers for radio
-   transmitters generally do not register to the input layer, unless the
-   device really provides an input device (i.e. a button that has no
-   effect other than generating a button press event)
-
- * The rfkill-input code hooks up to these events and switches the soft-block
-   of the various radio transmitters, depending on the button type.
-
- * The rfkill drivers turn off/on their transmitters as requested.
-
- * The rfkill class will generate userspace notifications (uevents) to tell
-   userspace what the current state is.
+or from query_hw_block) set_block() will be invoked for additional software
+block, but drivers can ignore the method call since they can use the return
+value of the function rfkill_set_hw_state() to sync the software state
+instead of keeping track of calls to set_block(). In fact, drivers should
+use the return value of rfkill_set_hw_state() unless the hardware actually
+keeps track of soft and hard block separately.

 
 
 
 

+3. Kernel API

 
 

-3. Kernel driver guidelines

 
 

-
-Drivers for radio transmitters normally implement only the rfkill class.
-These drivers may not unblock the transmitter based on own decisions, they
-should act on information provided by the rfkill class only.
+Drivers for radio transmitters normally implement an rfkill driver.

 
 Platform drivers might implement input devices if the rfkill button is just
 that, a button. If that button influences the hardware then you need to
 
 Platform drivers might implement input devices if the rfkill button is just
 that, a button. If that button influences the hardware then you need to

-implement an rfkill class instead. This also applies if the platform provides
+implement an rfkill driver instead. This also applies if the platform provides

 a way to turn on/off the transmitter(s).
 
 a way to turn on/off the transmitter(s).
 

-During suspend/hibernation, transmitters should only be left enabled when
-wake-on wlan or similar functionality requires it and the device wasn't
-blocked before suspend/hibernate. Note that it may be necessary to update
-the rfkill subsystem's idea of what the current state is at resume time if
-the state may have changed over suspend.
-
+For some platforms, it is possible that the hardware state changes during
+suspend/hibernation, in which case it will be necessary to update the rfkill
+core with the current state is at resume time.

 
 

+To create an rfkill driver, driver's Kconfig needs to have

 
 

-4. Kernel API
+       depends on RFKILL || !RFKILL

 
 

-To build a driver with rfkill subsystem support, the driver should depend on
-(or select) the Kconfig symbol RFKILL.
-
-The hardware the driver talks to may be write-only (where the current state
-of the hardware is unknown), or read-write (where the hardware can be queried
-about its current state).
+to ensure the driver cannot be built-in when rfkill is modular. The !RFKILL
+case allows the driver to be built when rfkill is not configured, which which
+case all rfkill API can still be used but will be provided by static inlines
+which compile to almost nothing.

 
 Calling rfkill_set_hw_state() when a state change happens is required from
 rfkill drivers that control devices that can be hard-blocked unless they also
 
 Calling rfkill_set_hw_state() when a state change happens is required from
 rfkill drivers that control devices that can be hard-blocked unless they also


@@ -105,10 +84,35 @@ device). Don't do this unless you cannot get the event in any other way.
 
 5. Userspace support
 
 
 5. Userspace support
 

-The following sysfs entries exist for every rfkill device:
+The recommended userspace interface to use is /dev/rfkill, which is a misc
+character device that allows userspace to obtain and set the state of rfkill
+devices and sets of devices. It also notifies userspace about device addition
+and removal. The API is a simple read/write API that is defined in
+linux/rfkill.h, with one ioctl that allows turning off the deprecated input
+handler in the kernel for the transition period.
+
+Except for the one ioctl, communication with the kernel is done via read()
+and write() of instances of 'struct rfkill_event'. In this structure, the
+soft and hard block are properly separated (unlike sysfs, see below) and
+userspace is able to get a consistent snapshot of all rfkill devices in the
+system. Also, it is possible to switch all rfkill drivers (or all drivers of
+a specified type) into a state which also updates the default state for
+hotplugged devices.
+
+After an application opens /dev/rfkill, it can read the current state of
+all devices, and afterwards can poll the descriptor for hotplug or state
+change events.
+
+Applications must ignore operations (the "op" field) they do not handle,
+this allows the API to be extended in the future.
+
+Additionally, each rfkill device is registered in sysfs and there has the
+following attributes:

 
        name: Name assigned by driver to this key (interface or driver name).
 
        name: Name assigned by driver to this key (interface or driver name).

-       type: Name of the key type ("wlan", "bluetooth", etc).
+       type: Driver type string ("wlan", "bluetooth", etc).
+       persistent: Whether the soft blocked state is initialised from
+                   non-volatile storage at startup.

        state: Current state of the transmitter
                0: RFKILL_STATE_SOFT_BLOCKED
                        transmitter is turned off by software
        state: Current state of the transmitter
                0: RFKILL_STATE_SOFT_BLOCKED
                        transmitter is turned off by software


@@ -117,7 +121,12 @@ The following sysfs entries exist for every rfkill device:
                2: RFKILL_STATE_HARD_BLOCKED
                        transmitter is forced off by something outside of
                        the driver's control.
                2: RFKILL_STATE_HARD_BLOCKED
                        transmitter is forced off by something outside of
                        the driver's control.

-       claim: 0: Kernel handles events (currently always reads that value)
+              This file is deprecated because it can only properly show
+              three of the four possible states, soft-and-hard-blocked is
+              missing.
+       claim: 0: Kernel handles events
+              This file is deprecated because there no longer is a way to
+              claim just control over a single rfkill instance.

 
 rfkill devices also issue uevents (with an action of "change"), with the
 following environment variables set:
 
 rfkill devices also issue uevents (with an action of "change"), with the
 following environment variables set:


@@ -128,9 +137,3 @@ RFKILL_TYPE
 
 The contents of these variables corresponds to the "name", "state" and
 "type" sysfs files explained above.
 
 The contents of these variables corresponds to the "name", "state" and
 "type" sysfs files explained above.

-
-An alternative userspace interface exists as a misc device /dev/rfkill,
-which allows userspace to obtain and set the state of rfkill devices and
-sets of devices. It also notifies userspace about device addition and
-removal. The API is a simple read/write API that is defined in
-linux/rfkill.h.