[PATCH 02/39] wimax: declarations for the in-kernel WiMAX API

Inaky Perez-Gonzalez
2008-11-26T22:41:12Z

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/net/wimax.h | 568 +++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 568 insertions(+), 0 deletions(-)
create mode 100644 include/net/wimax.h

diff --git a/include/net/wimax.h b/include/net/wimax.h
new file mode 100644
index 0000000..1e8bbf8
--- /dev/null
+++ b/include/net/wimax.h
@@ -0,0 +1,568 @@
+/*
+ * 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` in the device's private structure,
+ * initialize and register it. For details, see `struct
+ * wimax_dev`s documentation.
+ *
+ * Once this is done, wimax-tools's libwimax can be used to
+ * communicate with the driver from user space.
+ *
+ * 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 generit netlink (other
+ * methods can be added as needed).
+ *
+ * For user-to-kernel traffic 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. For kernel-to-user
+ * (notifications) we use messages over multicast groups. This way we
+ * can have multiple applications monitoring them.
+ *
+ * Each WiMAX network interface gets assigned a unique Generic Netlink
+ * Family ID (named "WiMAX <IFACEINDEX>").
+ *
+ * This makes it easy (and cheap) to map device to family ID
+ * considering that most deployments will have a single WiMAX device
+ * per system (without any limits on how many WiMAX adaptors per
+ * device might be present). For details, see file
+ * drivers/net/wimax/id-table.c.
+ *
+ * It also makes it easy to do traffic segregation using different
+ * multicast groups, that allow many applications to listen for
+ * notifications without being disrupted by the amount of traffic sent
+ * to other groups.
+ *
+ * User space must explicitly send an open command to the kernel [use
+ * libwimax:wimax_open()] to open a WiMAX handle. The kernel replies
+ * with information about the device that user space will need to talk
+ * to it. Once done, liwimax:wimax_close() releases the handle. No
+ * handle state information is maintained in the kernel (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
+ * the WiMAX API.
+ *
+ * At open time, an 'open' command is issued; that returns interface
+ * information and with it, the API version the kernel is currently
+ * exporting.
+ *
+ * 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 verion: 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.
+ *
+ * libwimax:wimax_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 create
+ * any number of pipes through which it can send
+ * messages/notifications to user space. User space can also send
+ * messages through the messaging pipe back to kernel space. See
+ * drivers/net/wimax/op-msg.c for details.
+ *
+ * The kernel-to-user messages are sent with wimax_pipe_msg(), over a
+ * generic netlink multicast group named after the pipe name and
+ * associated to the device's generic netlink family.
+ *
+ * There is always a default pipe created, the messaging pipe. It's up
+ * to the driver to create other pipes (for example, to send a lot of
+ * diagnostics information).
+ *
+ * The bidirectional messaging interface is built over said
+ * "messaging" pipe [which always exists], and the functions
+ * wimax_msg_*() are already setup to work with it. Messages from user
+ * space are sent as unicast and received by the kernel driver through
+ * 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 wimax_pipe;
+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.
+ * 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.
+ *
+ * @pipe_list: [private] List of registered pipes.
+ *
+ * @pipe_msg: [private] Generic Netlink multicast group for the
+ * driver to report answers to messages and driver-specific
+ * reports.
+ *
+ * @mutex: [private] Serializes all concurrent access and execution of
+ * operations.
+ *
+ * @state: [private] Current state of the WiMAX device.
+ *
+ * @gnl_family: [private] Generic Netlink pipe ID.
+ *
+ * @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 net_dev->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.
+ *
+ * This will populate sysfs entries in the device's directory that tag
+ * it as a device that supports the WiMAX interface (for
+ * userspace). 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 list_head pipe_list;
+ struct wimax_pipe *pipe_msg;
+ struct mutex mutex; /* Protects all members and API calls */
+ enum wimax_st state;
+
+ int (*op_msg_from_user)(struct wimax_dev *wimax_dev,
+ 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 genl_family gnl_family;
+ struct rfkill *rfkill;
+ struct input_dev *rfkill_input;
+ unsigned rf_hw;
+ unsigned rf_sw;
+ char name[32];
+};
+
+
+
+/*
+ * 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 message sending over pipes
+ *
+ * This is a facility for sending messages/notifications to user
+ * space over "pipes".
+ *
+ * There is one pipe created by default, the "msg" pipe (which is
+ * bidirectional); drivers can create others for sending notifications
+ * with wimax_pipe_add() and wimax_pipe_rm(). Mostly useful for
+ * multiplexing chunks of unrelated information (like high-bandwidth
+ * traces, diagnostics, etc) over each pipe without disturbing each
+ * other's listeners.
+ *
+ * pipe_handle = wimax_pipe_add(wimax_dev, "PIPENAME");
+ * ...
+ * wimax_pipe_msg*(wimax_dev, pipe_handle, ...);
+ * ...
+ * wimax_pipe_rm(wimax_dev, pipe_handle);
+ *
+ * In user space, use libwimax's pipe facilities to read from them.
+ */
+extern struct wimax_pipe *wimax_pipe_add(struct wimax_dev *, const char *);
+extern void wimax_pipe_rm(struct wimax_dev *, struct wimax_pipe *);
+
+/*
+ * Sending a message over a pipe:
+ *
+ * Sending a buffer:
+ *
+ * wimax_pipe_msg(wimax_dev, pipe_handle, buf, buf_size, GFP_KERNEL);
+ *
+ * Broken up:
+ *
+ * skb = wimax_pipe_msg_alloc(wimax_dev, pipe_handle, buf_size, GFP_KERNEL);
+ * ...fill up skb...
+ * wimax_pipe_msg_send(wimax_dev, pipe_handle, skb);
+ *
+ * Be sure not to modify skb->data in the middle (ie: don't use
+ * skb_push()/skb_pull()/skb_reserve() on the skb).
+ */
+extern struct sk_buff *wimax_pipe_msg_alloc(struct wimax_dev *,
+ const void *, size_t, gfp_t);
+extern int wimax_pipe_msg_send(struct wimax_dev *, struct wimax_pipe *,
+ struct sk_buff *);
+extern int wimax_pipe_msg(struct wimax_dev *, struct wimax_pipe *,
+ const void *, size_t, gfp_t);
+
+extern const void *wimax_msg_data(struct sk_buff *);
+extern ssize_t wimax_msg_len(struct sk_buff *);
+
+
+/*
+ * Same as before, but default to the "msg" pipe; as well, data
+ * can be received from user space (the wimax_dev->op_msg_from_user())
+ * will be called for each message sent.
+ */
+static inline
+struct sk_buff *wimax_msg_to_user_alloc(struct wimax_dev *wimax_dev,
+ const void *msg, size_t size, gfp_t gfp)
+{
+ return wimax_pipe_msg_alloc(wimax_dev, msg, size, gfp);
+}
+
+static inline
+int wimax_msg_to_user_send(struct wimax_dev *wimax_dev, struct sk_buff *skb)
+{
+ return wimax_pipe_msg_send(wimax_dev, wimax_dev->pipe_msg, skb);
+}
+
+static inline
+int wimax_msg_to_user(struct wimax_dev *wimax_dev,
+ const void *buf, size_t size, gfp_t gfp)
+{
+ return wimax_pipe_msg(wimax_dev, wimax_dev->pipe_msg,
+ buf, size, gfp);
+}
+
+
+/*
+ * 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__ */
--
1.5.6.5