uwb: add the uwb include files

Signed-off-by: David Vrabel <david.vrabel@csr.com>

1 files changed, 761 insertions, 0 deletions

diff --git a/include/linux/uwb.h b/include/linux/uwb.h
new file mode 100644
index 00000000000..0cd35937e12
--- /dev/null
+++ b/include/linux/uwb.h
@@ -0,0 +1,761 @@
+/*
+ * Ultra Wide Band
+ * UWB API
+ *
+ * Copyright (C) 2005-2006 Intel Corporation
+ * 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.
+ *
+ *
+ * FIXME: doc: overview of the API, different parts and pointers
+ */
+
+#ifndef __LINUX__UWB_H__
+#define __LINUX__UWB_H__
+
+#include <linux/limits.h>
+#include <linux/device.h>
+#include <linux/mutex.h>
+#include <linux/timer.h>
+#include <linux/workqueue.h>
+#include <linux/uwb/spec.h>
+
+struct uwb_dev;
+struct uwb_beca_e;
+struct uwb_rc;
+struct uwb_rsv;
+struct uwb_dbg;
+
+/**
+ * struct uwb_dev - a UWB Device
+ * @rc: UWB Radio Controller that discovered the device (kind of its
+ *     parent).
+ * @bce: a beacon cache entry for this device; or NULL if the device
+ *     is a local radio controller.
+ * @mac_addr: the EUI-48 address of this device.
+ * @dev_addr: the current DevAddr used by this device.
+ * @beacon_slot: the slot number the beacon is using.
+ * @streams: bitmap of streams allocated to reservations targeted at
+ *     this device.  For an RC, this is the streams allocated for
+ *     reservations targeted at DevAddrs.
+ *
+ * A UWB device may either by a neighbor or part of a local radio
+ * controller.
+ */
+struct uwb_dev {
+	struct mutex mutex;
+	struct list_head list_node;
+	struct device dev;
+	struct uwb_rc *rc;		/* radio controller */
+	struct uwb_beca_e *bce;		/* Beacon Cache Entry */
+
+	struct uwb_mac_addr mac_addr;
+	struct uwb_dev_addr dev_addr;
+	int beacon_slot;
+	DECLARE_BITMAP(streams, UWB_NUM_STREAMS);
+};
+#define to_uwb_dev(d) container_of(d, struct uwb_dev, dev)
+
+/**
+ * UWB HWA/WHCI Radio Control {Command|Event} Block context IDs
+ *
+ * RC[CE]Bs have a 'context ID' field that matches the command with
+ * the event received to confirm it.
+ *
+ * Maximum number of context IDs
+ */
+enum { UWB_RC_CTX_MAX = 256 };
+
+
+/** Notification chain head for UWB generated events to listeners */
+struct uwb_notifs_chain {
+	struct list_head list;
+	struct mutex mutex;
+};
+
+/**
+ * struct uwb_mas_bm - a bitmap of all MAS in a superframe
+ * @bm: a bitmap of length #UWB_NUM_MAS
+ */
+struct uwb_mas_bm {
+	DECLARE_BITMAP(bm, UWB_NUM_MAS);
+};
+
+/**
+ * uwb_rsv_state - UWB Reservation state.
+ *
+ * NONE - reservation is not active (no DRP IE being transmitted).
+ *
+ * Owner reservation states:
+ *
+ * INITIATED - owner has sent an initial DRP request.
+ * PENDING - target responded with pending Reason Code.
+ * MODIFIED - reservation manager is modifying an established
+ * reservation with a different MAS allocation.
+ * ESTABLISHED - the reservation has been successfully negotiated.
+ *
+ * Target reservation states:
+ *
+ * DENIED - request is denied.
+ * ACCEPTED - request is accepted.
+ * PENDING - PAL has yet to make a decision to whether to accept or
+ * deny.
+ *
+ * FIXME: further target states TBD.
+ */
+enum uwb_rsv_state {
+	UWB_RSV_STATE_NONE,
+	UWB_RSV_STATE_O_INITIATED,
+	UWB_RSV_STATE_O_PENDING,
+	UWB_RSV_STATE_O_MODIFIED,
+	UWB_RSV_STATE_O_ESTABLISHED,
+	UWB_RSV_STATE_T_ACCEPTED,
+	UWB_RSV_STATE_T_DENIED,
+	UWB_RSV_STATE_T_PENDING,
+
+	UWB_RSV_STATE_LAST,
+};
+
+enum uwb_rsv_target_type {
+	UWB_RSV_TARGET_DEV,
+	UWB_RSV_TARGET_DEVADDR,
+};
+
+/**
+ * struct uwb_rsv_target - the target of a reservation.
+ *
+ * Reservations unicast and targeted at a single device
+ * (UWB_RSV_TARGET_DEV); or (e.g., in the case of WUSB) targeted at a
+ * specific (private) DevAddr (UWB_RSV_TARGET_DEVADDR).
+ */
+struct uwb_rsv_target {
+	enum uwb_rsv_target_type type;
+	union {
+		struct uwb_dev *dev;
+		struct uwb_dev_addr devaddr;
+	};
+};
+
+/*
+ * Number of streams reserved for reservations targeted at DevAddrs.
+ */
+#define UWB_NUM_GLOBAL_STREAMS 1
+
+typedef void (*uwb_rsv_cb_f)(struct uwb_rsv *rsv);
+
+/**
+ * struct uwb_rsv - a DRP reservation
+ *
+ * Data structure management:
+ *
+ * @rc:             the radio controller this reservation is for
+ *                  (as target or owner)
+ * @rc_node:        a list node for the RC
+ * @pal_node:       a list node for the PAL
+ *
+ * Owner and target parameters:
+ *
+ * @owner:          the UWB device owning this reservation
+ * @target:         the target UWB device
+ * @type:           reservation type
+ *
+ * Owner parameters:
+ *
+ * @max_mas:        maxiumum number of MAS
+ * @min_mas:        minimum number of MAS
+ * @sparsity:       owner selected sparsity
+ * @is_multicast:   true iff multicast
+ *
+ * @callback:       callback function when the reservation completes
+ * @pal_priv:       private data for the PAL making the reservation
+ *
+ * Reservation status:
+ *
+ * @status:         negotiation status
+ * @stream:         stream index allocated for this reservation
+ * @mas:            reserved MAS
+ * @drp_ie:         the DRP IE
+ * @ie_valid:       true iff the DRP IE matches the reservation parameters
+ *
+ * DRP reservations are uniquely identified by the owner, target and
+ * stream index.  However, when using a DevAddr as a target (e.g., for
+ * a WUSB cluster reservation) the responses may be received from
+ * devices with different DevAddrs.  In this case, reservations are
+ * uniquely identified by just the stream index.  A number of stream
+ * indexes (UWB_NUM_GLOBAL_STREAMS) are reserved for this.
+ */
+struct uwb_rsv {
+	struct uwb_rc *rc;
+	struct list_head rc_node;
+	struct list_head pal_node;
+
+	struct uwb_dev *owner;
+	struct uwb_rsv_target target;
+	enum uwb_drp_type type;
+	int max_mas;
+	int min_mas;
+	int sparsity;
+	bool is_multicast;
+
+	uwb_rsv_cb_f callback;
+	void *pal_priv;
+
+	enum uwb_rsv_state state;
+	u8 stream;
+	struct uwb_mas_bm mas;
+	struct uwb_ie_drp *drp_ie;
+	bool ie_valid;
+	struct timer_list timer;
+	bool expired;
+};
+
+static const
+struct uwb_mas_bm uwb_mas_bm_zero = { .bm = { 0 } };
+
+static inline void uwb_mas_bm_copy_le(void *dst, const struct uwb_mas_bm *mas)
+{
+	bitmap_copy_le(dst, mas->bm, UWB_NUM_MAS);
+}
+
+/**
+ * struct uwb_drp_avail - a radio controller's view of MAS usage
+ * @global:   MAS unused by neighbors (excluding reservations targetted
+ *            or owned by the local radio controller) or the beaon period
+ * @local:    MAS unused by local established reservations
+ * @pending:  MAS unused by local pending reservations
+ * @ie:       DRP Availability IE to be included in the beacon
+ * @ie_valid: true iff @ie is valid and does not need to regenerated from
+ *            @global and @local
+ *
+ * Each radio controller maintains a view of MAS usage or
+ * availability. MAS available for a new reservation are determined
+ * from the intersection of @global, @local, and @pending.
+ *
+ * The radio controller must transmit a DRP Availability IE that's the
+ * intersection of @global and @local.
+ *
+ * A set bit indicates the MAS is unused and available.
+ *
+ * rc->rsvs_mutex should be held before accessing this data structure.
+ *
+ * [ECMA-368] section 17.4.3.
+ */
+struct uwb_drp_avail {
+	DECLARE_BITMAP(global, UWB_NUM_MAS);
+	DECLARE_BITMAP(local, UWB_NUM_MAS);
+	DECLARE_BITMAP(pending, UWB_NUM_MAS);
+	struct uwb_ie_drp_avail ie;
+	bool ie_valid;
+};
+
+
+const char *uwb_rsv_state_str(enum uwb_rsv_state state);
+const char *uwb_rsv_type_str(enum uwb_drp_type type);
+
+struct uwb_rsv *uwb_rsv_create(struct uwb_rc *rc, uwb_rsv_cb_f cb,
+			       void *pal_priv);
+void uwb_rsv_destroy(struct uwb_rsv *rsv);
+
+int uwb_rsv_establish(struct uwb_rsv *rsv);
+int uwb_rsv_modify(struct uwb_rsv *rsv,
+		   int max_mas, int min_mas, int sparsity);
+void uwb_rsv_terminate(struct uwb_rsv *rsv);
+
+void uwb_rsv_accept(struct uwb_rsv *rsv, uwb_rsv_cb_f cb, void *pal_priv);
+
+/**
+ * Radio Control Interface instance
+ *
+ *
+ * Life cycle rules: those of the UWB Device.
+ *
+ * @index:    an index number for this radio controller, as used in the
+ *            device name.
+ * @version:  version of protocol supported by this device
+ * @priv:     Backend implementation; rw with uwb_dev.dev.sem taken.
+ * @cmd:      Backend implementation to execute commands; rw and call
+ *            only  with uwb_dev.dev.sem taken.
+ * @reset:    Hardware reset of radio controller and any PAL controllers.
+ * @filter:   Backend implementation to manipulate data to and from device
+ *            to be compliant to specification assumed by driver (WHCI
+ *            0.95).
+ *
+ *            uwb_dev.dev.mutex is used to execute commands and update
+ *            the corresponding structures; can't use a spinlock
+ *            because rc->cmd() can sleep.
+ * @ies:         This is a dynamically allocated array cacheing the
+ *               IEs (settable by the host) that the beacon of this
+ *               radio controller is currently sending.
+ *
+ *               In reality, we store here the full command we set to
+ *               the radio controller (which is basically a command
+ *               prefix followed by all the IEs the beacon currently
+ *               contains). This way we don't have to realloc and
+ *               memcpy when setting it.
+ *
+ *               We set this up in uwb_rc_ie_setup(), where we alloc
+ *               this struct, call get_ie() [so we know which IEs are
+ *               currently being sent, if any].
+ *
+ * @ies_capacity:Amount of space (in bytes) allocated in @ies. The
+ *               amount used is given by sizeof(*ies) plus ies->wIELength
+ *               (which is a little endian quantity all the time).
+ * @ies_mutex:   protect the IE cache
+ * @dbg:         information for the debug interface
+ */
+struct uwb_rc {
+	struct uwb_dev uwb_dev;
+	int index;
+	u16 version;
+
+	struct module *owner;
+	void *priv;
+	int (*start)(struct uwb_rc *rc);
+	void (*stop)(struct uwb_rc *rc);
+	int (*cmd)(struct uwb_rc *, const struct uwb_rccb *, size_t);
+	int (*reset)(struct uwb_rc *rc);
+	int (*filter_cmd)(struct uwb_rc *, struct uwb_rccb **, size_t *);
+	int (*filter_event)(struct uwb_rc *, struct uwb_rceb **, const size_t,
+			    size_t *, size_t *);
+
+	spinlock_t neh_lock;		/* protects neh_* and ctx_* */
+	struct list_head neh_list;	/* Open NE handles */
+	unsigned long ctx_bm[UWB_RC_CTX_MAX / 8 / sizeof(unsigned long)];
+	u8 ctx_roll;
+
+	int beaconing;			/* Beaconing state [channel number] */
+	int scanning;
+	enum uwb_scan_type scan_type:3;
+	unsigned ready:1;
+	struct uwb_notifs_chain notifs_chain;
+
+	struct uwb_drp_avail drp_avail;
+	struct list_head reservations;
+	struct mutex rsvs_mutex;
+	struct workqueue_struct *rsv_workq;
+	struct work_struct rsv_update_work;
+
+	struct mutex ies_mutex;
+	struct uwb_rc_cmd_set_ie *ies;
+	size_t ies_capacity;
+
+	spinlock_t pal_lock;
+	struct list_head pals;
+
+	struct uwb_dbg *dbg;
+};
+
+
+/**
+ * struct uwb_pal - a UWB PAL
+ * @new_rsv: called when a peer requests a reservation (may be NULL if
+ *           the PAL cannot accept reservation requests).
+ *
+ * A Protocol Adaptation Layer (PAL) is a user of the WiMedia UWB
+ * radio platform (e.g., WUSB, WLP or Bluetooth UWB AMP).
+ *
+ * The PALs using a radio controller must register themselves to
+ * permit the UWB stack to coordinate usage of the radio between the
+ * various PALs or to allow PALs to response to certain requests from
+ * peers.
+ *
+ * A struct uwb_pal should be embedded in a containing structure
+ * belonging to the PAL and initialized with uwb_pal_init()).  Fields
+ * should be set appropriately by the PAL before registering the PAL
+ * with uwb_pal_register().
+ */
+struct uwb_pal {
+	struct list_head node;
+
+	void (*new_rsv)(struct uwb_rsv *rsv);
+};
+
+void uwb_pal_init(struct uwb_pal *pal);
+int uwb_pal_register(struct uwb_rc *rc, struct uwb_pal *pal);
+void uwb_pal_unregister(struct uwb_rc *rc, struct uwb_pal *pal);
+
+/*
+ * General public API
+ *
+ * This API can be used by UWB device drivers or by those implementing
+ * UWB Radio Controllers
+ */
+struct uwb_dev *uwb_dev_get_by_devaddr(struct uwb_rc *rc,
+				       const struct uwb_dev_addr *devaddr);
+struct uwb_dev *uwb_dev_get_by_rc(struct uwb_dev *, struct uwb_rc *);
+static inline void uwb_dev_get(struct uwb_dev *uwb_dev)
+{
+	get_device(&uwb_dev->dev);
+}
+static inline void uwb_dev_put(struct uwb_dev *uwb_dev)
+{
+	put_device(&uwb_dev->dev);
+}
+struct uwb_dev *uwb_dev_try_get(struct uwb_rc *rc, struct uwb_dev *uwb_dev);
+
+/**
+ * Callback function for 'uwb_{dev,rc}_foreach()'.
+ *
+ * @dev:  Linux device instance
+ *        'uwb_dev = container_of(dev, struct uwb_dev, dev)'
+ * @priv: Data passed by the caller to 'uwb_{dev,rc}_foreach()'.
+ *
+ * @returns: 0 to continue the iterations, any other val to stop
+ *           iterating and return the value to the caller of
+ *           _foreach().
+ */
+typedef int (*uwb_dev_for_each_f)(struct device *dev, void *priv);
+int uwb_dev_for_each(struct uwb_rc *rc, uwb_dev_for_each_f func, void *priv);
+
+struct uwb_rc *uwb_rc_alloc(void);
+struct uwb_rc *uwb_rc_get_by_dev(const struct uwb_dev_addr *);
+struct uwb_rc *uwb_rc_get_by_grandpa(const struct device *);
+void uwb_rc_put(struct uwb_rc *rc);
+
+typedef void (*uwb_rc_cmd_cb_f)(struct uwb_rc *rc, void *arg,
+                                struct uwb_rceb *reply, ssize_t reply_size);
+
+int uwb_rc_cmd_async(struct uwb_rc *rc, const char *cmd_name,
+		     struct uwb_rccb *cmd, size_t cmd_size,
+		     u8 expected_type, u16 expected_event,
+		     uwb_rc_cmd_cb_f cb, void *arg);
+ssize_t uwb_rc_cmd(struct uwb_rc *rc, const char *cmd_name,
+		   struct uwb_rccb *cmd, size_t cmd_size,
+		   struct uwb_rceb *reply, size_t reply_size);
+ssize_t uwb_rc_vcmd(struct uwb_rc *rc, const char *cmd_name,
+		    struct uwb_rccb *cmd, size_t cmd_size,
+		    u8 expected_type, u16 expected_event,
+		    struct uwb_rceb **preply);
+ssize_t uwb_rc_get_ie(struct uwb_rc *, struct uwb_rc_evt_get_ie **);
+int uwb_bg_joined(struct uwb_rc *rc);
+
+size_t __uwb_addr_print(char *, size_t, const unsigned char *, int);
+
+int uwb_rc_dev_addr_set(struct uwb_rc *, const struct uwb_dev_addr *);
+int uwb_rc_dev_addr_get(struct uwb_rc *, struct uwb_dev_addr *);
+int uwb_rc_mac_addr_set(struct uwb_rc *, const struct uwb_mac_addr *);
+int uwb_rc_mac_addr_get(struct uwb_rc *, struct uwb_mac_addr *);
+int __uwb_mac_addr_assigned_check(struct device *, void *);
+int __uwb_dev_addr_assigned_check(struct device *, void *);
+
+/* Print in @buf a pretty repr of @addr */
+static inline size_t uwb_dev_addr_print(char *buf, size_t buf_size,
+					const struct uwb_dev_addr *addr)
+{
+	return __uwb_addr_print(buf, buf_size, addr->data, 0);
+}
+
+/* Print in @buf a pretty repr of @addr */
+static inline size_t uwb_mac_addr_print(char *buf, size_t buf_size,
+					const struct uwb_mac_addr *addr)
+{
+	return __uwb_addr_print(buf, buf_size, addr->data, 1);
+}
+
+/* @returns 0 if device addresses @addr2 and @addr1 are equal */
+static inline int uwb_dev_addr_cmp(const struct uwb_dev_addr *addr1,
+				   const struct uwb_dev_addr *addr2)
+{
+	return memcmp(addr1, addr2, sizeof(*addr1));
+}
+
+/* @returns 0 if MAC addresses @addr2 and @addr1 are equal */
+static inline int uwb_mac_addr_cmp(const struct uwb_mac_addr *addr1,
+				   const struct uwb_mac_addr *addr2)
+{
+	return memcmp(addr1, addr2, sizeof(*addr1));
+}
+
+/* @returns !0 if a MAC @addr is a broadcast address */
+static inline int uwb_mac_addr_bcast(const struct uwb_mac_addr *addr)
+{
+	struct uwb_mac_addr bcast = {
+		.data = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff }
+	};
+	return !uwb_mac_addr_cmp(addr, &bcast);
+}
+
+/* @returns !0 if a MAC @addr is all zeroes*/
+static inline int uwb_mac_addr_unset(const struct uwb_mac_addr *addr)
+{
+	struct uwb_mac_addr unset = {
+		.data = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }
+	};
+	return !uwb_mac_addr_cmp(addr, &unset);
+}
+
+/* @returns !0 if the address is in use. */
+static inline unsigned __uwb_dev_addr_assigned(struct uwb_rc *rc,
+					       struct uwb_dev_addr *addr)
+{
+	return uwb_dev_for_each(rc, __uwb_dev_addr_assigned_check, addr);
+}
+
+/*
+ * UWB Radio Controller API
+ *
+ * This API is used (in addition to the general API) to implement UWB
+ * Radio Controllers.
+ */
+void uwb_rc_init(struct uwb_rc *);
+int uwb_rc_add(struct uwb_rc *, struct device *dev, void *rc_priv);
+void uwb_rc_rm(struct uwb_rc *);
+void uwb_rc_neh_grok(struct uwb_rc *, void *, size_t);
+void uwb_rc_neh_error(struct uwb_rc *, int);
+void uwb_rc_reset_all(struct uwb_rc *rc);
+
+/**
+ * uwb_rsv_is_owner - is the owner of this reservation the RC?
+ * @rsv: the reservation
+ */
+static inline bool uwb_rsv_is_owner(struct uwb_rsv *rsv)
+{
+	return rsv->owner == &rsv->rc->uwb_dev;
+}
+
+/**
+ * Events generated by UWB that can be passed to any listeners
+ *
+ * Higher layers can register callback functions with the radio
+ * controller using uwb_notifs_register(). The radio controller
+ * maintains a list of all registered handlers and will notify all
+ * nodes when an event occurs.
+ */
+enum uwb_notifs {
+	UWB_NOTIF_BG_JOIN = 0,	/* radio controller joined a beacon group */
+	UWB_NOTIF_BG_LEAVE = 1,	/* radio controller left a beacon group */
+	UWB_NOTIF_ONAIR,
+	UWB_NOTIF_OFFAIR,
+};
+
+/* Callback function registered with UWB */
+struct uwb_notifs_handler {
+	struct list_head list_node;
+	void (*cb)(void *, struct uwb_dev *, enum uwb_notifs);
+	void *data;
+};
+
+int uwb_notifs_register(struct uwb_rc *, struct uwb_notifs_handler *);
+int uwb_notifs_deregister(struct uwb_rc *, struct uwb_notifs_handler *);
+
+
+/**
+ * UWB radio controller Event Size Entry (for creating entry tables)
+ *
+ * WUSB and WHCI define events and notifications, and they might have
+ * fixed or variable size.
+ *
+ * Each event/notification has a size which is not necessarily known
+ * in advance based on the event code. As well, vendor specific
+ * events/notifications will have a size impossible to determine
+ * unless we know about the device's specific details.
+ *
+ * It was way too smart of the spec writers not to think that it would
+ * be impossible for a generic driver to skip over vendor specific
+ * events/notifications if there are no LENGTH fields in the HEADER of
+ * each message...the transaction size cannot be counted on as the
+ * spec does not forbid to pack more than one event in a single
+ * transaction.
+ *
+ * Thus, we guess sizes with tables (or for events, when you know the
+ * size ahead of time you can use uwb_rc_neh_extra_size*()). We
+ * register tables with the known events and their sizes, and then we
+ * traverse those tables. For those with variable length, we provide a
+ * way to lookup the size inside the event/notification's
+ * payload. This allows device-specific event size tables to be
+ * registered.
+ *
+ * @size:   Size of the payload
+ *
+ * @offset: if != 0, at offset @offset-1 starts a field with a length
+ *          that has to be added to @size. The format of the field is
+ *          given by @type.
+ *
+ * @type:   Type and length of the offset field. Most common is LE 16
+ *          bits (that's why that is zero); others are there mostly to
+ *          cover for bugs and weirdos.
+ */
+struct uwb_est_entry {
+	size_t size;
+	unsigned offset;
+	enum { UWB_EST_16 = 0, UWB_EST_8 = 1 } type;
+};
+
+int uwb_est_register(u8 type, u8 code_high, u16 vendor, u16 product,
+		     const struct uwb_est_entry *, size_t entries);
+int uwb_est_unregister(u8 type, u8 code_high, u16 vendor, u16 product,
+		       const struct uwb_est_entry *, size_t entries);
+ssize_t uwb_est_find_size(struct uwb_rc *rc, const struct uwb_rceb *rceb,
+			  size_t len);
+
+/* -- Misc */
+
+enum {
+	EDC_MAX_ERRORS = 10,
+	EDC_ERROR_TIMEFRAME = HZ,
+};
+
+/* error density counter */
+struct edc {
+	unsigned long timestart;
+	u16 errorcount;
+};
+
+static inline
+void edc_init(struct edc *edc)
+{
+	edc->timestart = jiffies;
+}
+
+/* Called when an error occured.
+ * This is way to determine if the number of acceptable errors per time
+ * period has been exceeded. It is not accurate as there are cases in which
+ * this scheme will not work, for example if there are periodic occurences
+ * of errors that straddle updates to the start time. This scheme is
+ * sufficient for our usage.
+ *
+ * @returns 1 if maximum acceptable errors per timeframe has been exceeded.
+ */
+static inline int edc_inc(struct edc *err_hist, u16 max_err, u16 timeframe)
+{
+	unsigned long now;
+
+	now = jiffies;
+	if (now - err_hist->timestart > timeframe) {
+		err_hist->errorcount = 1;
+		err_hist->timestart = now;
+	} else if (++err_hist->errorcount > max_err) {
+			err_hist->errorcount = 0;
+			err_hist->timestart = now;
+			return 1;
+	}
+	return 0;
+}
+
+
+/* Information Element handling */
+
+/* For representing the state of writing to a buffer when iterating */
+struct uwb_buf_ctx {
+	char *buf;
+	size_t bytes, size;
+};
+
+typedef int (*uwb_ie_f)(struct uwb_dev *, const struct uwb_ie_hdr *,
+			size_t, void *);
+struct uwb_ie_hdr *uwb_ie_next(void **ptr, size_t *len);
+ssize_t uwb_ie_for_each(struct uwb_dev *uwb_dev, uwb_ie_f fn, void *data,
+			const void *buf, size_t size);
+int uwb_ie_dump_hex(struct uwb_dev *, const struct uwb_ie_hdr *,
+		    size_t, void *);
+int uwb_rc_set_ie(struct uwb_rc *, struct uwb_rc_cmd_set_ie *);
+struct uwb_ie_hdr *uwb_ie_next(void **ptr, size_t *len);
+
+
+/*
+ * Transmission statistics
+ *
+ * UWB uses LQI and RSSI (one byte values) for reporting radio signal
+ * strength and line quality indication. We do quick and dirty
+ * averages of those. They are signed values, btw.
+ *
+ * For 8 bit quantities, we keep the min, the max, an accumulator
+ * (@sigma) and a # of samples. When @samples gets to 255, we compute
+ * the average (@sigma / @samples), place it in @sigma and reset
+ * @samples to 1 (so we use it as the first sample).
+ *
+ * Now, statistically speaking, probably I am kicking the kidneys of
+ * some books I have in my shelves collecting dust, but I just want to
+ * get an approx, not the Nobel.
+ *
+ * LOCKING: there is no locking per se, but we try to keep a lockless
+ * schema. Only _add_samples() modifies the values--as long as you
+ * have other locking on top that makes sure that no two calls of
+ * _add_sample() happen at the same time, then we are fine. Now, for
+ * resetting the values we just set @samples to 0 and that makes the
+ * next _add_sample() to start with defaults. Reading the values in
+ * _show() currently can race, so you need to make sure the calls are
+ * under the same lock that protects calls to _add_sample(). FIXME:
+ * currently unlocked (It is not ultraprecise but does the trick. Bite
+ * me).
+ */
+struct stats {
+	s8 min, max;
+	s16 sigma;
+	atomic_t samples;
+};
+
+static inline
+void stats_init(struct stats *stats)
+{
+	atomic_set(&stats->samples, 0);
+	wmb();
+}
+
+static inline
+void stats_add_sample(struct stats *stats, s8 sample)
+{
+	s8 min, max;
+	s16 sigma;
+	unsigned samples = atomic_read(&stats->samples);
+	if (samples == 0) {	/* it was zero before, so we initialize */
+		min = 127;
+		max = -128;
+		sigma = 0;
+	} else {
+		min = stats->min;
+		max = stats->max;
+		sigma = stats->sigma;
+	}
+
+	if (sample < min)	/* compute new values */
+		min = sample;
+	else if (sample > max)
+		max = sample;
+	sigma += sample;
+
+	stats->min = min;	/* commit */
+	stats->max = max;
+	stats->sigma = sigma;
+	if (atomic_add_return(1, &stats->samples) > 255) {
+		/* wrapped around! reset */
+		stats->sigma = sigma / 256;
+		atomic_set(&stats->samples, 1);
+	}
+}
+
+static inline ssize_t stats_show(struct stats *stats, char *buf)
+{
+	int min, max, avg;
+	int samples = atomic_read(&stats->samples);
+	if (samples == 0)
+		min = max = avg = 0;
+	else {
+		min = stats->min;
+		max = stats->max;
+		avg = stats->sigma / samples;
+	}
+	return scnprintf(buf, PAGE_SIZE, "%d %d %d\n", min, max, avg);
+}
+
+static inline ssize_t stats_store(struct stats *stats, const char *buf,
+				  size_t size)
+{
+	stats_init(stats);
+	return size;
+}
+
+#endif /* #ifndef __LINUX__UWB_H__ */