Patchwork [02/29] wimax: headers for kernel API and user space interaction

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Submitter Inaky Perez-Gonzalez
Date Dec. 21, 2008, 12:57 a.m.
Message ID <963f349c513a2df72f20f25f039e061f24678ac7.1229820957.git.inaky@linux.intel.com>
Download mbox | patch
Permalink /patch/15121/
State Not Applicable
Delegated to: David Miller
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Comments

Inaky Perez-Gonzalez - Dec. 21, 2008, 12:57 a.m.
Definitions for the user/kernel API protocol through generic
netlink. User space can copy it verbatim and use it.

Kernel API definition declares the main data types and calls for the
drivers to integrate into the WiMAX stack. Provides usage
documentation.

Signed-off-by: Inaky Perez-Gonzalez <inaky@linux.intel.com>
---
 include/linux/wimax.h |  234 ++++++++++++++++++++++
 include/net/wimax.h   |  520 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 754 insertions(+), 0 deletions(-)
 create mode 100644 include/linux/wimax.h
 create mode 100644 include/net/wimax.h

Patch

diff --git a/include/linux/wimax.h b/include/linux/wimax.h
new file mode 100644
index 0000000..c89de7f
--- /dev/null
+++ b/include/linux/wimax.h
@@ -0,0 +1,234 @@ 
+/*
+ * Linux WiMax
+ * API for user space
+ *
+ *
+ * Copyright (C) 2007-2008 Intel Corporation. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ *   * Redistributions of source code must retain the above copyright
+ *     notice, this list of conditions and the following disclaimer.
+ *   * Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in
+ *     the documentation and/or other materials provided with the
+ *     distribution.
+ *   * Neither the name of Intel Corporation nor the names of its
+ *     contributors may be used to endorse or promote products derived
+ *     from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ *
+ * Intel Corporation <linux-wimax@intel.com>
+ * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
+ *  - Initial implementation
+ *
+ *
+ * This file declares the user/kernel protocol that is spoken over
+ * Generic Netlink, as well as any type declaration that is to be used
+ * by kernel and user space.
+ *
+ * It is intended for user space to clone it verbatim to use it as a
+ * primary reference for definitions.
+ *
+ * Stuff intended for kernel usage as well as full protocol and stack
+ * documentation is rooted in include/net/wimax.h.
+ */
+
+#ifndef __LINUX__WIMAX_H__
+#define __LINUX__WIMAX_H__
+
+#include <linux/types.h>
+
+enum {
+	/**
+	 * Version of the interface (unsigned decimal, MMm, max 25.5)
+	 * M - Major: change if removing or modifying an existing call.
+	 * m - minor: change when adding a new call
+	 */
+	WIMAX_GNL_VERSION = 00,
+	/* Generic NetLink attributes */
+	WIMAX_GNL_ATTR_INVALID = 0x00,
+	WIMAX_GNL_ATTR_MAX = 10,
+};
+
+
+/*
+ * Generic NetLink operations
+ *
+ * Most of these map to an API call; _OP_ stands for operation, _RP_
+ * for reply and _RE_ for report (aka: signal).
+ */
+enum {
+	WIMAX_GNL_OP_MSG_FROM_USER,	/* User to kernel message */
+	WIMAX_GNL_OP_MSG_TO_USER,	/* Kernel to user message */
+	WIMAX_GNL_OP_RFKILL,	/* Run wimax_rfkill() */
+	WIMAX_GNL_OP_RESET,	/* Run wimax_rfkill() */
+	WIMAX_GNL_RE_STATE_CHANGE,	/* Report: status change */
+};
+
+
+/* Message from user / to user */
+enum {
+	WIMAX_GNL_MSG_IFIDX = 1,
+	WIMAX_GNL_MSG_PIPE_NAME,
+	WIMAX_GNL_MSG_DATA,
+};
+
+
+/*
+ * wimax_rfkill()
+ *
+ * The state of the radio (ON/OFF) is mapped to the rfkill subsystem's
+ * switch state (DISABLED/ENABLED).
+ */
+enum wimax_rf_state {
+	WIMAX_RF_OFF = 0,	/* Radio is off, rfkill on/enabled */
+	WIMAX_RF_ON = 1,	/* Radio is on, rfkill off/disabled */
+	WIMAX_RF_QUERY = 2,
+};
+
+/* Attributes */
+enum {
+	WIMAX_GNL_RFKILL_IFIDX = 1,
+	WIMAX_GNL_RFKILL_STATE,
+};
+
+
+/* Attributes for wimax_reset() */
+enum {
+	WIMAX_GNL_RESET_IFIDX = 1,
+};
+
+
+/*
+ * Attributes for the Report State Change
+ *
+ * For now we just have the old and new states; new attributes might
+ * be added later on.
+ */
+enum {
+	WIMAX_GNL_STCH_IFIDX = 1,
+	WIMAX_GNL_STCH_STATE_OLD,
+	WIMAX_GNL_STCH_STATE_NEW,
+};
+
+
+/**
+ * enum wimax_st - The different states of a WiMAX device
+ * @__WIMAX_ST_NULL: The device structure has been allocated and zeroed,
+ *     but still wimax_dev_add() hasn't been called. There is no state.
+ *
+ * @WIMAX_ST_DOWN: The device has been registered with the WiMAX and
+ *     networking stacks, but it is not initialized (normally that is
+ *     done with 'ifconfig DEV up' [or equivalent], which can upload
+ *     firmware and enable communications with the device).
+ *     In this state, the device is powered down and using as less
+ *     power as possible.
+ *     This state is the default after a call to wimax_dev_add(). It
+ *     is ok to have drivers move directly to %WIMAX_ST_UNINITIALIZED
+ *     or %WIMAX_ST_RADIO_OFF in _probe() after the call to
+ *     wimax_dev_add().
+ *     It is recommended that the driver leaves this state when
+ *     calling 'ifconfig DEV up' and enters it back on 'ifconfig DEV
+ *     down'.
+ *
+ * @__WIMAX_ST_QUIESCING: The device is being torn down, so no API
+ *     operations are allowed to proceed except the ones needed to
+ *     complete the device clean up process.
+ *
+ * @WIMAX_ST_UNINITIALIZED: [optional] Communication with the device
+ *     is setup, but the device still requires some configuration
+ *     before being operational.
+ *     Some WiMAX API calls might work.
+ *
+ * @WIMAX_ST_RADIO_OFF: The device is fully up; radio is off (wether
+ *     by hardware or software switches).
+ *     It is recommended to always leave the device in this state
+ *     after initialization.
+ *
+ * @WIMAX_ST_READY: The device is fully up and radio is on.
+ *
+ * @WIMAX_ST_SCANNING: [optional] The device has been instructed to
+ *     scan. In this state, the device cannot be actively connected to
+ *     a network.
+ *
+ * @WIMAX_ST_CONNECTING: The device is connecting to a network. This
+ *     state exists because in some devices, the connect process can
+ *     include a number of negotiations between user space, kernel
+ *     space and the device. User space needs to know what the device
+ *     is doing. If the connect sequence in a device is atomic and
+ *     fast, the device can transition directly to CONNECTED
+ *
+ * @WIMAX_ST_CONNECTED: The device is connected to a network.
+ *
+ * @__WIMAX_ST_INVALID: This is an invalid state used to mark the
+ *     maximum numeric value of states.
+ *
+ * Description:
+ *
+ * Transitions from one state to another one are atomic and can only
+ * be caused in kernel space with wimax_state_change(). To read the
+ * state, use wimax_state_get().
+ *
+ * States starting with __ are internal and shall not be used or
+ * referred to by drivers or userspace. They look ugly, but that's the
+ * point -- if any use is made non-internal to the stack, it is easier
+ * to catch on review.
+ *
+ * All API operations [with well defined exceptions] will take the
+ * device mutex before starting and then check the state. If the state
+ * is %__WIMAX_ST_NULL, %WIMAX_ST_DOWN, %WIMAX_ST_UNINITIALIZED or
+ * %__WIMAX_ST_QUIESCING, it will drop the lock and quit with
+ * -%EINVAL, -%ENOMEDIUM, -%ENOTCONN or -%ESHUTDOWN.
+ *
+ * The order of the definitions is important, so we can do numerical
+ * comparisons (eg: < %WIMAX_ST_RADIO_OFF means the device is not ready
+ * to operate).
+ */
+/*
+ * The allowed state transitions are described in the table below
+ * (states in rows can go to states in columns where there is an X):
+ *
+ *                                  UNINI   RADIO READY SCAN CONNEC CONNEC
+ *             NULL DOWN QUIESCING TIALIZED  OFF        NING  TING   TED
+ * NULL         -    x
+ * DOWN              -      x        x       x
+ * QUIESCING         x      -
+ * UNINITIALIZED            x        -       x
+ * RADIO_OFF                x                -     x
+ * READY                    x                x     -     x     x      x
+ * SCANNING                 x                x     x     -     x      x
+ * CONNECTING               x                x     x     x     -      x
+ * CONNECTED                x                x     x                  -
+ *
+ * This table not available in kernel-doc because the formatting messes it up.
+ */
+ enum wimax_st {
+	__WIMAX_ST_NULL = 0,
+	WIMAX_ST_DOWN,
+	__WIMAX_ST_QUIESCING,
+	WIMAX_ST_UNINITIALIZED,
+	WIMAX_ST_RADIO_OFF,
+	WIMAX_ST_READY,
+	WIMAX_ST_SCANNING,
+	WIMAX_ST_CONNECTING,
+	WIMAX_ST_CONNECTED,
+	__WIMAX_ST_INVALID			/* Always keep last */
+};
+
+
+#endif /* #ifndef __LINUX__WIMAX_H__ */
diff --git a/include/net/wimax.h b/include/net/wimax.h
new file mode 100644
index 0000000..1602614
--- /dev/null
+++ b/include/net/wimax.h
@@ -0,0 +1,520 @@ 
+/*
+ * Linux WiMAX
+ * Kernel space API for accessing WiMAX devices
+ *
+ *
+ * Copyright (C) 2007-2008 Intel Corporation <linux-wimax@intel.com>
+ * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version
+ * 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ *
+ *
+ * The WiMAX stack provides an API for controlling and managing the
+ * system's WiMAX devices. This API affects the control plane; the
+ * data plane is accessed via the network stack (netdev).
+ *
+ * Parts of the WiMAX stack API and notifications are exported to
+ * user space via Generic Netlink. In user space, libwimax (part of
+ * the wimax-tools package) provides a shim layer for accessing those
+ * calls.
+ *
+ * The API is standarized for all WiMAX devices and different drivers
+ * implement the backend support for it. However, device-specific
+ * messaging pipes are provided that can be used to issue commands and
+ * receive notifications in free form.
+ *
+ * Currently the messaging pipes are the only means of control as it
+ * is not known (due to the lack of more devices in the market) what
+ * will be a good abstraction layer. Expect this to change as more
+ * devices show in the market. This API is designed to be growable in
+ * order to address this problem.
+ *
+ * USAGE
+ *
+ * Embed a `struct wimax_dev` at the beginning of the the device's
+ * private structure, initialize and register it. For details, see
+ * `struct wimax_dev`s documentation.
+ *
+ * Once this is done, wimax-tools's libwimaxll can be used to
+ * communicate with the driver from user space. You user space
+ * application does not have to forcibily use libwimaxll and can talk
+ * the generic netlink protocol directly if desired.
+ *
+ * Remember this is a very low level API that will to provide all of
+ * WiMAX features. Other daemons and services running in user space
+ * are the expected clients of it. They offer a higher level API that
+ * applications should use (an example of this is the Intel's WiMAX
+ * Network Service for the i2400m).
+ *
+ * DESIGN
+ *
+ * Although not set on final stone, this very basic interface is
+ * mostly completed. Remember this is meant to grow as new common
+ * operations are decided upon. New operations will be added to the
+ * interface, intent being on keeping backwards compatibility as much
+ * as possible.
+ *
+ * This layer implements a set of calls to control a WiMAX device,
+ * exposing a frontend to the rest of the kernel and user space (via
+ * generic netlink) and a backend implementation in the driver through
+ * function pointers.
+ *
+ * WiMAX devices have a state, and a kernel-only API allows the
+ * drivers to manipulate that state. State transitions are atomic, and
+ * only some of them are allowed (see `enum wimax_st`).
+ *
+ * Most API calls will set the state automatically; in most cases
+ * drivers have to only report state changes due to external
+ * conditions.
+ *
+ * All API operations are 'atomic', serialized thorough a mutex in the
+ * `struct wimax_dev`.
+ *
+ * EXPORTING TO USER SPACE THROUGH GENERIC NETLINK
+ *
+ * The API is exported to user space using generic netlink (other
+ * methods can be added as needed).
+ *
+ * There is a Generic Netlink Family named "WiMAX", where interfaces
+ * supporting the WiMAX interface receive commands and broadcast their
+ * signals over a multicast group named "msg".
+ *
+ * Mapping to the source/destination interface is done by an interface
+ * index attribute.
+ *
+ * For user-to-kernel traffic (commands) we use a function call
+ * marshalling mechanism, where a message X with attributes A, B, C
+ * sent from user space to kernel space means executing the WiMAX API
+ * call wimax_X(A, B, C), sending the results back as a message.
+ *
+ * Kernel-to-user (notifications or signals) communication is sent
+ * over multicast groups. This allows to have multiple applications
+ * monitoring them.
+ *
+ * Each command/signal gets assigned it's own attribute policy. This
+ * way the validator will verify that all the attributes in there are
+ * only the ones that should be for each command/signal. Thing of an
+ * attribute mapping to a type+argumentname for each command/signal.
+ *
+ * If we had a single policy for *all* commands/signals, after running
+ * the validator we'd have to check "does this attribute belong in
+ * here"?  for each one. It can be done manually, but it's just easier
+ * to have the validator do that job with multiple policies. As well,
+ * it makes it easier to later expand each command/signal signature
+ * without affecting others and keeping the namespace more or less
+ * sane. Not that it is too complicated, but it makes it even easier.
+ *
+ * No state information is maintained in the kernel for each user
+ * space connection (the connection is stateless).
+ *
+ * TESTING FOR THE INTERFACE AND VERSIONING
+ *
+ * If network interface X is a WiMAX device, there will be a Generic
+ * Netlink family named "WiMAX X" and the device will present a
+ * "wimax" directory in it's network sysfs directory
+ * (/sys/class/net/DEVICE/wimax) [used by HAL].
+ *
+ * The inexistence of any of these means the device does not support
+ * this WiMAX API.
+ *
+ * By querying the generic netlink controller, versioning information
+ * and the multicast groups available can be found. Applications using
+ * the interface can either rely on that or use the generic netlink
+ * controller to figure out which generic netlink commands/signals are
+ * supported.
+ *
+ * NOTE: this versioning is a last resort to avoid hard
+ *    incompatibilities. It is the intention of the design of this
+ *    stack not to introduce backward incompatible changes.
+ *
+ * The version code has to fit in one byte (restrictions imposed by
+ * generic netlink); we use `version / 10` for the major version and
+ * `version % 10` for the minor. This gives 9 minors for each major
+ * and 25 majors.
+ *
+ * The version change protocol is as follow:
+ *
+ * - Major versions: needs to be increased if an existing message/API
+ *   call is changed or removed. Doesn't need to be changed if a new
+ *   message is added.
+ *
+ * - Minor version: needs to be increased if new messages/API calls are
+ *   being added or some other consideration that doesn't impact the
+ *   user-kernel interface too much (like some kind of bug fix) and
+ *   that is kind of left up in the air to common sense.
+ *
+ * User space code should not try to work if the major version it was
+ * compiled for differs from what the kernel offers. As well, if the
+ * minor version of the kernel interface is lower than the one user
+ * space is expecting (the one it was compiled for), the kernel
+ * might be missing API calls; user space shall be ready to handle
+ * said condition. Use the generic netlink controller operations to
+ * find which ones are supported and which not.
+ *
+ * libwimaxll:wimaxll_open() takes care of checking versions.
+ *
+ * THE OPERATIONS:
+ *
+ * Each operation is defined in its on file (drivers/net/wimax/op-*.c)
+ * for clarity. The parts needed for an operation are:
+ *
+ *  - a function pointer in `struct wimax_dev`: optional, as the
+ *    operation might be implemented by the stack and not by the
+ *    driver.
+ *
+ *    All function pointers are named wimax_dev->op_*(), and drivers
+ *    must implement them except where noted otherwise.
+ *
+ *  - When exported to user space, a `struct nla_policy` to define the
+ *    attributes of the generic netlink command and a `struct genl_ops`
+ *    to define the operation.
+ *
+ * All the declarations for the operation codes (WIMAX_GNL_OP_<NAME>)
+ * and generic netlink attributes (WIMAX_GNL_<NAME>_*) are declared in
+ * include/linux/wimax.h; this file is intended to be cloned by user
+ * space to gain access to those declarations.
+ *
+ * A few caveats to remember:
+ *
+ *  - Need to define attribute numbers starting in 1; otherwise it
+ *    fails.
+ *
+ *  - the `struct genl_family` requires a maximum attribute id; when
+ *    defining the `struct nla_policy` for each message, it has to have
+ *    an array size of WIMAX_GNL_ATTR_MAX+1.
+ *
+ * THE PIPE INTERFACE:
+ *
+ * This interface is kept intentionally simple. The driver can send
+ * and receive free-form messages to/from user space through a
+ * pipe. See drivers/net/wimax/op-msg.c for details.
+ *
+ * The kernel-to-user messages are sent with
+ * wimax_msg(). user-to-kernel messages are delivered via
+ * wimax_dev->op_msg_from_user().
+ *
+ * RFKILL:
+ *
+ * RFKILL support is built into the wimax_dev layer; the driver just
+ * needs to call wimax_report_rfkill_{hw,sw}() to inform of changes in
+ * the hardware or software RF kill switches. When the stack wants to
+ * turn the radio off, it will call wimax_dev->op_rfkill_sw_toggle(),
+ * which the driver implements.
+ *
+ * User space can set the software RF Kill switch by calling
+ * wimax_rfkill().
+ *
+ * The code for now only supports devices that don't require polling;
+ * If the device needs to be polled, create a self-rearming delayed
+ * work struct for polling or look into adding polled support to the
+ * WiMAX stack.
+ *
+ * When initializing the hardware (_probe), after calling
+ * wimax_dev_add(), query the device for it's RF Kill switches status
+ * and feed it back to the WiMAX stack using
+ * wimax_report_rfkill_{hw,sw}(). If any switch is missing, always
+ * report it as ON.
+ *
+ * NOTE: the wimax stack uses an inverted terminology to that of the
+ * RFKILL subsystem:
+ *
+ *  - ON: radio is ON, RFKILL is DISABLED or OFF.
+ *  - OFF: radio is OFF, RFKILL is ENABLED or ON.
+ *
+ * MISCELLANEOUS OPS:
+ *
+ * wimax_reset() can be used to reset the device to power on state; by
+ * default it issues a warm reset that maintains the same device
+ * node. If that is not possible, it falls back to a cold reset
+ * (device reconnect). The driver implements the backend to this
+ * through wimax_dev->op_reset().
+ */
+
+#ifndef __NET__WIMAX_H__
+#define __NET__WIMAX_H__
+#ifdef __KERNEL__
+
+#include <linux/wimax.h>
+#include <net/genetlink.h>
+#include <linux/netdevice.h>
+
+struct net_device;
+struct genl_info;
+struct wimax_dev;
+struct input_dev;
+
+/**
+ * struct wimax_dev - Generic WiMAX device
+ *
+ * @net_dev: [fill] Pointer to the &struct net_device this WiMAX
+ *     device implements.
+ *
+ * @op_msg_from_user: [fill] Driver-specific operation to
+ *     handle a raw message from user space to the driver. The
+ *     driver can send messages to user space using with
+ *     wimax_msg_to_user().
+ *
+ * @op_rfkill_sw_toggle: [fill] Driver-specific operation to act on
+ *     userspace (or any other agent) requesting the WiMAX device to
+ *     change the RF Kill software switch (WIMAX_RF_ON or
+ *     WIMAX_RF_OFF).
+ *     If such hardware support is not present, it is assumed the
+ *     radio cannot be switched off and it is always on (and the stack
+ *     will error out when trying to switch it off). In such case,
+ *     this function pointer can be left as NULL.
+ *
+ * @op_reset: [fill] Driver specific operation to reset the
+ *     device.
+ *     This operation should always attempt first a warm reset that
+ *     does not disconnect the device from the bus and return 0.
+ *     If that fails, it should resort to some sort of cold or bus
+ *     reset (even if it implies a bus disconnection and device
+ *     dissapearance). In that case, -ENODEV should be returned to
+ *     indicate the device is gone.
+ *     This operation has to be synchronous, and return only when the
+ *     reset is complete. In case of having had to resort to bus/cold
+ *     reset implying a device disconnection, the call is allowed to
+ *     return inmediately.
+ *     NOTE: wimax_dev->mutex is NOT locked when this op is being
+ *     called; however, wimax_dev->mutex_reset IS locked to ensure
+ *     serialization of calls to wimax_reset().
+ *     See wimax_reset()'s documentation.
+ *
+ * @name: [fill] A way to identify this device. We need to register a
+ *     name with many subsystems (input for RFKILL, workqueue
+ *     creation, etc). We can't use the network device name as that
+ *     might change and in some instances we don't know it yet (until
+ *     we don't call register_netdev()). So we generate an unique one
+ *     using the driver name and device bus id, place it here and use
+ *     it across the board. Recommended naming:
+ *     DRIVERNAME-BUSNAME:BUSID (dev->bus->name, dev->bus_id).
+ *
+ * @id_table_node: [private] link to the list of wimax devices kept by
+ *     id-table.c. Protected by it's own spinlock.
+ *
+ * @mutex: [private] Serializes all concurrent access and execution of
+ *     operations.
+ *
+ * @mutex_reset: [private] Serializes reset operations. Needs to be a
+ *     different mutex because as part of the reset operation, the
+ *     driver has to call back into the stack to do things such as
+ *     state change, that require wimax_dev->mutex.
+ *
+ * @state: [private] Current state of the WiMAX device.
+ *
+ * @rfkill: [private] integration into the RF-Kill infrastructure.
+ *
+ * @rfkill_input: [private] virtual input device to process the
+ *     hardware RF Kill switches.
+ *
+ * @rf_sw: [private] State of the software radio switch (OFF/ON)
+ *
+ * @rf_hw: [private] State of the hardware radio switch (OFF/ON)
+ *
+ * Description:
+ * This structure defines a common interface to access all WiMAX
+ * devices from different vendors and provides a common API as well as
+ * a free-form device-specific messaging channel.
+ *
+ * Usage:
+ *  1. Embed a &struct wimax_dev at *the beginning* the network
+ *     device structure so that netdev_priv() points to it.
+ *
+ *  2. memset() it to zero
+ *
+ *  3. Initialize with wimax_dev_init(). This will leave the WiMAX
+ *     device in the %__WIMAX_ST_NULL state.
+ *
+ *  4. Fill all the fields marked with [fill]; once called
+ *     wimax_dev_add(), those fields CANNOT be modified.
+ *
+ *  5. Call wimax_dev_add() *after* registering the network
+ *     device. This will leave the WiMAX device in the %WIMAX_ST_DOWN
+ *     state.
+ *     Protect the driver's net_device->open() against succeeding if
+ *     the wimax device state is lower than %WIMAX_ST_DOWN.
+ *
+ *  6. Select when the device is going to be turned on/initialized;
+ *     for example, it could be initialized on 'ifconfig up' (when the
+ *     netdev op 'open()' is called on the driver).
+ *
+ * When the device is initialized (at `ifconfig up` time, or right
+ * after calling wimax_dev_add() from _probe(), make sure the
+ * following steps are taken
+ *
+ *  a. Move the device to %WIMAX_ST_UNINITIALIZED. This is needed so
+ *     some API calls that shouldn't work until the device is ready
+ *     can be blocked.
+ *
+ *  b. Initialize the device. Make sure to turn the SW radio switch
+ *     off and move the device to state %WIMAX_ST_RADIO_OFF when
+ *     done. When just initialized, a device should be left in RADIO
+ *     OFF state until user space devices to turn it on.
+ *
+ *  c. Query the device for the state of the hardware rfkill switch
+ *     and call wimax_rfkill_report_hw() and wimax_rfkill_report_sw()
+ *     as needed. See below.
+ *
+ * wimax_dev_rm() undoes before unregistering the network device. Once
+ * wimax_dev_add() is called, the driver can get called on the
+ * wimax_dev->op_* function pointers
+ *
+ * CONCURRENCY:
+ *
+ * The stack provides a mutex for each device that will disallow API
+ * calls happening concurrently; thus, op calls into the driver
+ * through the wimax_dev->op*() function pointers will always be
+ * serialized and *never* concurrent.
+ *
+ * For locking, take wimax_dev->mutex is taken; (most) operations in
+ * the API have to check for wimax_dev_is_ready() to return 0 before
+ * continuing (this is done internally).
+ *
+ * REFERENCE COUNTING:
+ *
+ * The WiMAX device is reference counted by the associated network
+ * device. The only operation that can be used to reference the device
+ * is wimax_dev_get_by_genl_info(), and the reference it acquires has
+ * to be released with dev_put(wimax_dev->net_dev).
+ *
+ * RFKILL:
+ *
+ * At startup, both HW and SW radio switchess are assumed to be off.
+ *
+ * At initialization time [after calling wimax_dev_add()], have the
+ * driver query the device for the status of the software and hardware
+ * RF kill switches and call wimax_report_rfkill_hw() and
+ * wimax_rfkill_report_sw() to indicate their state. If any is
+ * missing, just call it to indicate it is ON (radio always on).
+ *
+ * Whenever the driver detects a change in the state of the RF kill
+ * switches, it should call wimax_report_rfkill_hw() or
+ * wimax_report_rfkill_sw() to report it to the stack.
+ */
+struct wimax_dev {
+	struct net_device *net_dev;
+	struct list_head id_table_node;
+	struct mutex mutex;		/* Protects all members and API calls */
+	struct mutex mutex_reset;
+	enum wimax_st state;
+
+	int (*op_msg_from_user)(struct wimax_dev *wimax_dev,
+				const char *,
+				const void *, size_t,
+				const struct genl_info *info);
+	int (*op_rfkill_sw_toggle)(struct wimax_dev *wimax_dev,
+				   enum wimax_rf_state);
+	int (*op_reset)(struct wimax_dev *wimax_dev);
+
+	struct rfkill *rfkill;
+	struct input_dev *rfkill_input;
+	unsigned rf_hw;
+	unsigned rf_sw;
+	char name[32];
+
+	struct dentry *debugfs_dentry;
+};
+
+
+
+/*
+ * WiMAX stack public API for device drivers
+ * -----------------------------------------
+ *
+ * These functions are not exported to user space.
+ */
+extern void wimax_dev_init(struct wimax_dev *);
+extern int wimax_dev_add(struct wimax_dev *, struct net_device *);
+extern void wimax_dev_rm(struct wimax_dev *);
+
+static inline
+struct wimax_dev *net_dev_to_wimax(struct net_device *net_dev)
+{
+	return netdev_priv(net_dev);
+}
+
+static inline
+struct device *wimax_dev_to_dev(struct wimax_dev *wimax_dev)
+{
+	return wimax_dev->net_dev->dev.parent;
+}
+
+extern void wimax_state_change(struct wimax_dev *, enum wimax_st);
+extern enum wimax_st wimax_state_get(struct wimax_dev *);
+
+/*
+ * Radio Switch state reporting.
+ *
+ * enum wimax_rf_state is declared in linux/wimax.h so the exports
+ * to user space can use it.
+ */
+extern void wimax_report_rfkill_hw(struct wimax_dev *, enum wimax_rf_state);
+extern void wimax_report_rfkill_sw(struct wimax_dev *, enum wimax_rf_state);
+
+
+/*
+ * Free-form messaging to/from user space
+ *
+ * Sending a message:
+ *
+ *   wimax_msg(wimax_dev, pipe_name, buf, buf_size, GFP_KERNEL);
+ *
+ * Broken up:
+ *
+ *   skb = wimax_msg_alloc(wimax_dev, pipe_name, buf_size, GFP_KERNEL);
+ *   ...fill up skb...
+ *   wimax_msg_send(wimax_dev, pipe_name, skb);
+ *
+ * Be sure not to modify skb->data in the middle (ie: don't use
+ * skb_push()/skb_pull()/skb_reserve() on the skb).
+ *
+ * "pipe_name" is any string, than can be interpreted as the name of
+ * the pipe or destinatary; the interpretation of it is driver
+ * specific, so the recipient can multiplex it as wished. It can be
+ * NULL, it won't be used - an example is using a "diagnostics" tag to
+ * send diagnostics information that a device-specific diagnostics
+ * tool would be interested in.
+ */
+extern struct sk_buff *wimax_msg_alloc(struct wimax_dev *, const char *,
+				       const void *, size_t, gfp_t);
+extern int wimax_msg_send(struct wimax_dev *, struct sk_buff *);
+extern int wimax_msg(struct wimax_dev *, const char *,
+		     const void *, size_t, gfp_t);
+
+extern const void *wimax_msg_data_len(struct sk_buff *, size_t *);
+extern const void *wimax_msg_data(struct sk_buff *);
+extern ssize_t wimax_msg_len(struct sk_buff *);
+
+
+/*
+ * WiMAX stack user space API
+ * --------------------------
+ *
+ * This API is what gets exported to user space for general
+ * operations. As well, they can be called from within the kernel,
+ * (with a properly referenced `struct wimax_dev`).
+ *
+ * Properly referenced means: the 'struct net_device' that embeds the
+ * device's control structure and (as such) the 'struct wimax_dev' is
+ * referenced by the caller.
+ */
+extern int wimax_rfkill(struct wimax_dev *, enum wimax_rf_state);
+extern int wimax_reset(struct wimax_dev *);
+
+#else
+/* You might be looking for linux/wimax.h */
+#error This file should not be included from user space.
+#endif /* #ifdef __KERNEL__ */
+#endif /* #ifndef __NET__WIMAX_H__ */