uwb: add the UWB stack (MLME)

Most of the MAC Layer Management Entity (MLME) support: address, beacon, IE
and scan management.

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

1 files changed, 644 insertions, 0 deletions

diff --git a/drivers/uwb/beacon.c b/drivers/uwb/beacon.c
new file mode 100644
index 00000000000..f65a52c0afa
--- /dev/null
+++ b/drivers/uwb/beacon.c
@@ -0,0 +1,644 @@
+/*
+ * Ultra Wide Band
+ * Beacon management
+ *
+ * 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: docs
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/kdev_t.h>
+#include "uwb-internal.h"
+
+#define D_LOCAL 0
+#include <linux/uwb/debug.h>
+
+/** Start Beaconing command structure */
+struct uwb_rc_cmd_start_beacon {
+	struct uwb_rccb rccb;
+	__le16 wBPSTOffset;
+	u8 bChannelNumber;
+} __attribute__((packed));
+
+
+static int uwb_rc_start_beacon(struct uwb_rc *rc, u16 bpst_offset, u8 channel)
+{
+	int result;
+	struct uwb_rc_cmd_start_beacon *cmd;
+	struct uwb_rc_evt_confirm reply;
+
+	cmd = kzalloc(sizeof(*cmd), GFP_KERNEL);
+	if (cmd == NULL)
+		return -ENOMEM;
+	cmd->rccb.bCommandType = UWB_RC_CET_GENERAL;
+	cmd->rccb.wCommand = cpu_to_le16(UWB_RC_CMD_START_BEACON);
+	cmd->wBPSTOffset = cpu_to_le16(bpst_offset);
+	cmd->bChannelNumber = channel;
+	reply.rceb.bEventType = UWB_RC_CET_GENERAL;
+	reply.rceb.wEvent = UWB_RC_CMD_START_BEACON;
+	result = uwb_rc_cmd(rc, "START-BEACON", &cmd->rccb, sizeof(*cmd),
+			    &reply.rceb, sizeof(reply));
+	if (result < 0)
+		goto error_cmd;
+	if (reply.bResultCode != UWB_RC_RES_SUCCESS) {
+		dev_err(&rc->uwb_dev.dev,
+			"START-BEACON: command execution failed: %s (%d)\n",
+			uwb_rc_strerror(reply.bResultCode), reply.bResultCode);
+		result = -EIO;
+	}
+error_cmd:
+	kfree(cmd);
+	return result;
+}
+
+static int uwb_rc_stop_beacon(struct uwb_rc *rc)
+{
+	int result;
+	struct uwb_rccb *cmd;
+	struct uwb_rc_evt_confirm reply;
+
+	cmd = kzalloc(sizeof(*cmd), GFP_KERNEL);
+	if (cmd == NULL)
+		return -ENOMEM;
+	cmd->bCommandType = UWB_RC_CET_GENERAL;
+	cmd->wCommand = cpu_to_le16(UWB_RC_CMD_STOP_BEACON);
+	reply.rceb.bEventType = UWB_RC_CET_GENERAL;
+	reply.rceb.wEvent = UWB_RC_CMD_STOP_BEACON;
+	result = uwb_rc_cmd(rc, "STOP-BEACON", cmd, sizeof(*cmd),
+			    &reply.rceb, sizeof(reply));
+	if (result < 0)
+		goto error_cmd;
+	if (reply.bResultCode != UWB_RC_RES_SUCCESS) {
+		dev_err(&rc->uwb_dev.dev,
+			"STOP-BEACON: command execution failed: %s (%d)\n",
+			uwb_rc_strerror(reply.bResultCode), reply.bResultCode);
+		result = -EIO;
+	}
+error_cmd:
+	kfree(cmd);
+	return result;
+}
+
+/*
+ * Start/stop beacons
+ *
+ * @rc:          UWB Radio Controller to operate on
+ * @channel:     UWB channel on which to beacon (WUSB[table
+ *               5-12]). If -1, stop beaconing.
+ * @bpst_offset: Beacon Period Start Time offset; FIXME-do zero
+ *
+ * According to WHCI 0.95 [4.13.6] the driver will only receive the RCEB
+ * of a SET IE command after the device sent the first beacon that includes
+ * the IEs specified in the SET IE command. So, after we start beaconing we
+ * check if there is anything in the IE cache and call the SET IE command
+ * if needed.
+ */
+int uwb_rc_beacon(struct uwb_rc *rc, int channel, unsigned bpst_offset)
+{
+	int result;
+	struct device *dev = &rc->uwb_dev.dev;
+
+	mutex_lock(&rc->uwb_dev.mutex);
+	if (channel < 0)
+		channel = -1;
+	if (channel == -1)
+		result = uwb_rc_stop_beacon(rc);
+	else {
+		/* channel >= 0...dah */
+		result = uwb_rc_start_beacon(rc, bpst_offset, channel);
+		if (result < 0)
+			goto out_up;
+		if (le16_to_cpu(rc->ies->wIELength) > 0) {
+			result = uwb_rc_set_ie(rc, rc->ies);
+			if (result < 0) {
+				dev_err(dev, "Cannot set new IE on device: "
+					"%d\n", result);
+				result = uwb_rc_stop_beacon(rc);
+				channel = -1;
+				bpst_offset = 0;
+			} else
+				result = 0;
+		}
+	}
+
+	if (result < 0)
+		goto out_up;
+	rc->beaconing = channel;
+
+	uwb_notify(rc, NULL, uwb_bg_joined(rc) ? UWB_NOTIF_BG_JOIN : UWB_NOTIF_BG_LEAVE);
+
+out_up:
+	mutex_unlock(&rc->uwb_dev.mutex);
+	return result;
+}
+
+/*
+ * Beacon cache
+ *
+ * The purpose of this is to speed up the lookup of becon information
+ * when a new beacon arrives. The UWB Daemon uses it also to keep a
+ * tab of which devices are in radio distance and which not. When a
+ * device's beacon stays present for more than a certain amount of
+ * time, it is considered a new, usable device. When a beacon ceases
+ * to be received for a certain amount of time, it is considered that
+ * the device is gone.
+ *
+ * FIXME: use an allocator for the entries
+ * FIXME: use something faster for search than a list
+ */
+
+struct uwb_beca uwb_beca = {
+	.list = LIST_HEAD_INIT(uwb_beca.list),
+	.mutex = __MUTEX_INITIALIZER(uwb_beca.mutex)
+};
+
+
+void uwb_bce_kfree(struct kref *_bce)
+{
+	struct uwb_beca_e *bce = container_of(_bce, struct uwb_beca_e, refcnt);
+
+	kfree(bce->be);
+	kfree(bce);
+}
+
+
+/* Find a beacon by dev addr in the cache */
+static
+struct uwb_beca_e *__uwb_beca_find_bydev(const struct uwb_dev_addr *dev_addr)
+{
+	struct uwb_beca_e *bce, *next;
+	list_for_each_entry_safe(bce, next, &uwb_beca.list, node) {
+		d_printf(6, NULL, "looking for addr %02x:%02x in %02x:%02x\n",
+			 dev_addr->data[0], dev_addr->data[1],
+			 bce->dev_addr.data[0], bce->dev_addr.data[1]);
+		if (!memcmp(&bce->dev_addr, dev_addr, sizeof(bce->dev_addr)))
+			goto out;
+	}
+	bce = NULL;
+out:
+	return bce;
+}
+
+/* Find a beacon by dev addr in the cache */
+static
+struct uwb_beca_e *__uwb_beca_find_bymac(const struct uwb_mac_addr *mac_addr)
+{
+	struct uwb_beca_e *bce, *next;
+	list_for_each_entry_safe(bce, next, &uwb_beca.list, node) {
+		if (!memcmp(bce->mac_addr, mac_addr->data,
+			    sizeof(bce->mac_addr)))
+			goto out;
+	}
+	bce = NULL;
+out:
+	return bce;
+}
+
+/**
+ * uwb_dev_get_by_devaddr - get a UWB device with a specific DevAddr
+ * @rc:      the radio controller that saw the device
+ * @devaddr: DevAddr of the UWB device to find
+ *
+ * There may be more than one matching device (in the case of a
+ * DevAddr conflict), but only the first one is returned.
+ */
+struct uwb_dev *uwb_dev_get_by_devaddr(struct uwb_rc *rc,
+				       const struct uwb_dev_addr *devaddr)
+{
+	struct uwb_dev *found = NULL;
+	struct uwb_beca_e *bce;
+
+	mutex_lock(&uwb_beca.mutex);
+	bce = __uwb_beca_find_bydev(devaddr);
+	if (bce)
+		found = uwb_dev_try_get(rc, bce->uwb_dev);
+	mutex_unlock(&uwb_beca.mutex);
+
+	return found;
+}
+
+/**
+ * uwb_dev_get_by_macaddr - get a UWB device with a specific EUI-48
+ * @rc:      the radio controller that saw the device
+ * @devaddr: EUI-48 of the UWB device to find
+ */
+struct uwb_dev *uwb_dev_get_by_macaddr(struct uwb_rc *rc,
+				       const struct uwb_mac_addr *macaddr)
+{
+	struct uwb_dev *found = NULL;
+	struct uwb_beca_e *bce;
+
+	mutex_lock(&uwb_beca.mutex);
+	bce = __uwb_beca_find_bymac(macaddr);
+	if (bce)
+		found = uwb_dev_try_get(rc, bce->uwb_dev);
+	mutex_unlock(&uwb_beca.mutex);
+
+	return found;
+}
+
+/* Initialize a beacon cache entry */
+static void uwb_beca_e_init(struct uwb_beca_e *bce)
+{
+	mutex_init(&bce->mutex);
+	kref_init(&bce->refcnt);
+	stats_init(&bce->lqe_stats);
+	stats_init(&bce->rssi_stats);
+}
+
+/*
+ * Add a beacon to the cache
+ *
+ * @be:         Beacon event information
+ * @bf:         Beacon frame (part of b, really)
+ * @ts_jiffies: Timestamp (in jiffies) when the beacon was received
+ */
+struct uwb_beca_e *__uwb_beca_add(struct uwb_rc_evt_beacon *be,
+				  struct uwb_beacon_frame *bf,
+				  unsigned long ts_jiffies)
+{
+	struct uwb_beca_e *bce;
+
+	bce = kzalloc(sizeof(*bce), GFP_KERNEL);
+	if (bce == NULL)
+		return NULL;
+	uwb_beca_e_init(bce);
+	bce->ts_jiffies = ts_jiffies;
+	bce->uwb_dev = NULL;
+	list_add(&bce->node, &uwb_beca.list);
+	return bce;
+}
+
+/*
+ * Wipe out beacon entries that became stale
+ *
+ * Remove associated devicest too.
+ */
+void uwb_beca_purge(void)
+{
+	struct uwb_beca_e *bce, *next;
+	unsigned long now = jiffies;
+	mutex_lock(&uwb_beca.mutex);
+	list_for_each_entry_safe(bce, next, &uwb_beca.list, node) {
+		if (now - bce->ts_jiffies
+		    > msecs_to_jiffies(beacon_timeout_ms)) {
+			uwbd_dev_offair(bce);
+			list_del(&bce->node);
+			uwb_bce_put(bce);
+		}
+	}
+	mutex_unlock(&uwb_beca.mutex);
+}
+
+/* Clean up the whole beacon cache. Called on shutdown */
+void uwb_beca_release(void)
+{
+	struct uwb_beca_e *bce, *next;
+	mutex_lock(&uwb_beca.mutex);
+	list_for_each_entry_safe(bce, next, &uwb_beca.list, node) {
+		list_del(&bce->node);
+		uwb_bce_put(bce);
+	}
+	mutex_unlock(&uwb_beca.mutex);
+}
+
+static void uwb_beacon_print(struct uwb_rc *rc, struct uwb_rc_evt_beacon *be,
+			     struct uwb_beacon_frame *bf)
+{
+	char macbuf[UWB_ADDR_STRSIZE];
+	char devbuf[UWB_ADDR_STRSIZE];
+	char dstbuf[UWB_ADDR_STRSIZE];
+
+	uwb_mac_addr_print(macbuf, sizeof(macbuf), &bf->Device_Identifier);
+	uwb_dev_addr_print(devbuf, sizeof(devbuf), &bf->hdr.SrcAddr);
+	uwb_dev_addr_print(dstbuf, sizeof(dstbuf), &bf->hdr.DestAddr);
+	dev_info(&rc->uwb_dev.dev,
+		 "BEACON from %s to %s (ch%u offset %u slot %u MAC %s)\n",
+		 devbuf, dstbuf, be->bChannelNumber, be->wBPSTOffset,
+		 bf->Beacon_Slot_Number, macbuf);
+}
+
+/*
+ * @bce: beacon cache entry, referenced
+ */
+ssize_t uwb_bce_print_IEs(struct uwb_dev *uwb_dev, struct uwb_beca_e *bce,
+			  char *buf, size_t size)
+{
+	ssize_t result = 0;
+	struct uwb_rc_evt_beacon *be;
+	struct uwb_beacon_frame *bf;
+	struct uwb_buf_ctx ctx = {
+		.buf = buf,
+		.bytes = 0,
+		.size = size
+	};
+
+	mutex_lock(&bce->mutex);
+	be = bce->be;
+	if (be == NULL)
+		goto out;
+	bf = (void *) be->BeaconInfo;
+	uwb_ie_for_each(uwb_dev, uwb_ie_dump_hex, &ctx,
+			bf->IEData, be->wBeaconInfoLength - sizeof(*bf));
+	result = ctx.bytes;
+out:
+	mutex_unlock(&bce->mutex);
+	return result;
+}
+
+/*
+ * Verify that the beacon event, frame and IEs are ok
+ */
+static int uwb_verify_beacon(struct uwb_rc *rc, struct uwb_event *evt,
+			     struct uwb_rc_evt_beacon *be)
+{
+	int result = -EINVAL;
+	struct uwb_beacon_frame *bf;
+	struct device *dev = &rc->uwb_dev.dev;
+
+	/* Is there enough data to decode a beacon frame? */
+	if (evt->notif.size < sizeof(*be) + sizeof(*bf)) {
+		dev_err(dev, "BEACON event: Not enough data to decode "
+			"(%zu vs %zu bytes needed)\n", evt->notif.size,
+			sizeof(*be) + sizeof(*bf));
+		goto error;
+	}
+	/* FIXME: make sure beacon frame IEs are fine and that the whole thing
+	 * is consistent */
+	result = 0;
+error:
+	return result;
+}
+
+/*
+ * Handle UWB_RC_EVT_BEACON events
+ *
+ * We check the beacon cache to see how the received beacon fares. If
+ * is there already we refresh the timestamp. If not we create a new
+ * entry.
+ *
+ * According to the WHCI and WUSB specs, only one beacon frame is
+ * allowed per notification block, so we don't bother about scanning
+ * for more.
+ */
+int uwbd_evt_handle_rc_beacon(struct uwb_event *evt)
+{
+	int result = -EINVAL;
+	struct uwb_rc *rc;
+	struct uwb_rc_evt_beacon *be;
+	struct uwb_beacon_frame *bf;
+	struct uwb_beca_e *bce;
+	struct device *dev = &evt->rc->uwb_dev.dev;
+	unsigned long last_ts;
+
+	rc = evt->rc;
+	be = container_of(evt->notif.rceb, struct uwb_rc_evt_beacon, rceb);
+	result = uwb_verify_beacon(rc, evt, be);
+	if (result < 0)
+		return result;
+
+	/* Ignore beacon if it is from an alien. */
+	if (be->bBeaconType == UWB_RC_BEACON_TYPE_OL_ALIEN ||
+	    be->bBeaconType == UWB_RC_BEACON_TYPE_NOL_ALIEN) {
+		if (printk_ratelimit())
+			dev_err(dev, "BEACON received from ALIEN. Action? \n");
+		result = -ENOSYS;
+		return 0;
+	}
+	bf = (struct uwb_beacon_frame *) be->BeaconInfo;
+
+	/*
+	 * Drop beacons from devices with a NULL EUI-48 -- they cannot
+	 * be uniquely identified.
+	 *
+	 * It's expected that these will all be WUSB devices and they
+	 * have a WUSB specific connection method so ignoring them
+	 * here shouldn't be a problem.
+	 */
+	if (uwb_mac_addr_bcast(&bf->Device_Identifier))
+		return 0;
+
+	mutex_lock(&uwb_beca.mutex);
+	bce = __uwb_beca_find_bymac(&bf->Device_Identifier);
+	if (bce == NULL) {
+		/* Not in there, a new device is pinging */
+		uwb_beacon_print(evt->rc, be, bf);
+		bce = __uwb_beca_add(be, bf, evt->ts_jiffies);
+		if (bce == NULL) {
+			mutex_unlock(&uwb_beca.mutex);
+			return -ENOMEM;
+		}
+	}
+	mutex_unlock(&uwb_beca.mutex);
+
+	mutex_lock(&bce->mutex);
+	/* purge old beacon data */
+	kfree(bce->be);
+
+	last_ts = bce->ts_jiffies;
+
+	/* Update commonly used fields */
+	bce->ts_jiffies = evt->ts_jiffies;
+	bce->be = be;
+	bce->dev_addr = bf->hdr.SrcAddr;
+	bce->mac_addr = &bf->Device_Identifier;
+	be->wBPSTOffset = le16_to_cpu(be->wBPSTOffset);
+	be->wBeaconInfoLength = le16_to_cpu(be->wBeaconInfoLength);
+	stats_add_sample(&bce->lqe_stats, be->bLQI - 7);
+	stats_add_sample(&bce->rssi_stats, be->bRSSI + 18);
+
+	/*
+	 * This might be a beacon from a new device.
+	 */
+	if (bce->uwb_dev == NULL)
+		uwbd_dev_onair(evt->rc, bce);
+
+	mutex_unlock(&bce->mutex);
+
+	return 1; /* we keep the event data */
+}
+
+/*
+ * Handle UWB_RC_EVT_BEACON_SIZE events
+ *
+ * XXXXX
+ */
+int uwbd_evt_handle_rc_beacon_size(struct uwb_event *evt)
+{
+	int result = -EINVAL;
+	struct device *dev = &evt->rc->uwb_dev.dev;
+	struct uwb_rc_evt_beacon_size *bs;
+
+	/* Is there enough data to decode the event? */
+	if (evt->notif.size < sizeof(*bs)) {
+		dev_err(dev, "BEACON SIZE notification: Not enough data to "
+			"decode (%zu vs %zu bytes needed)\n",
+			evt->notif.size, sizeof(*bs));
+		goto error;
+	}
+	bs = container_of(evt->notif.rceb, struct uwb_rc_evt_beacon_size, rceb);
+	if (0)
+		dev_info(dev, "Beacon size changed to %u bytes "
+			"(FIXME: action?)\n", le16_to_cpu(bs->wNewBeaconSize));
+	else {
+		/* temporary hack until we do something with this message... */
+		static unsigned count;
+		if (++count % 1000 == 0)
+			dev_info(dev, "Beacon size changed %u times "
+				"(FIXME: action?)\n", count);
+	}
+	result = 0;
+error:
+	return result;
+}
+
+/**
+ * uwbd_evt_handle_rc_bp_slot_change - handle a BP_SLOT_CHANGE event
+ * @evt: the BP_SLOT_CHANGE notification from the radio controller
+ *
+ * If the event indicates that no beacon period slots were available
+ * then radio controller has transitioned to a non-beaconing state.
+ * Otherwise, simply save the current beacon slot.
+ */
+int uwbd_evt_handle_rc_bp_slot_change(struct uwb_event *evt)
+{
+	struct uwb_rc *rc = evt->rc;
+	struct device *dev = &rc->uwb_dev.dev;
+	struct uwb_rc_evt_bp_slot_change *bpsc;
+
+	if (evt->notif.size < sizeof(*bpsc)) {
+		dev_err(dev, "BP SLOT CHANGE event: Not enough data\n");
+		return -EINVAL;
+	}
+	bpsc = container_of(evt->notif.rceb, struct uwb_rc_evt_bp_slot_change, rceb);
+
+	mutex_lock(&rc->uwb_dev.mutex);
+	if (uwb_rc_evt_bp_slot_change_no_slot(bpsc)) {
+		dev_info(dev, "stopped beaconing: No free slots in BP\n");
+		rc->beaconing = -1;
+	} else
+		rc->uwb_dev.beacon_slot = uwb_rc_evt_bp_slot_change_slot_num(bpsc);
+	mutex_unlock(&rc->uwb_dev.mutex);
+
+	return 0;
+}
+
+/**
+ * Handle UWB_RC_EVT_BPOIE_CHANGE events
+ *
+ * XXXXX
+ */
+struct uwb_ie_bpo {
+	struct uwb_ie_hdr hdr;
+	u8                bp_length;
+	u8                data[];
+} __attribute__((packed));
+
+int uwbd_evt_handle_rc_bpoie_change(struct uwb_event *evt)
+{
+	int result = -EINVAL;
+	struct device *dev = &evt->rc->uwb_dev.dev;
+	struct uwb_rc_evt_bpoie_change *bpoiec;
+	struct uwb_ie_bpo *bpoie;
+	static unsigned count;	/* FIXME: this is a temp hack */
+	size_t iesize;
+
+	/* Is there enough data to decode it? */
+	if (evt->notif.size < sizeof(*bpoiec)) {
+		dev_err(dev, "BPOIEC notification: Not enough data to "
+			"decode (%zu vs %zu bytes needed)\n",
+			evt->notif.size, sizeof(*bpoiec));
+		goto error;
+	}
+	bpoiec = container_of(evt->notif.rceb, struct uwb_rc_evt_bpoie_change, rceb);
+	iesize = le16_to_cpu(bpoiec->wBPOIELength);
+	if (iesize < sizeof(*bpoie)) {
+		dev_err(dev, "BPOIEC notification: Not enough IE data to "
+			"decode (%zu vs %zu bytes needed)\n",
+			iesize, sizeof(*bpoie));
+		goto error;
+	}
+	if (++count % 1000 == 0)	/* Lame placeholder */
+		dev_info(dev, "BPOIE: %u changes received\n", count);
+	/*
+	 * FIXME: At this point we should go over all the IEs in the
+	 *        bpoiec->BPOIE array and act on each.
+	 */
+	result = 0;
+error:
+	return result;
+}
+
+/**
+ * uwb_bg_joined - is the RC in a beacon group?
+ * @rc: the radio controller
+ *
+ * Returns true if the radio controller is in a beacon group (even if
+ * it's the sole member).
+ */
+int uwb_bg_joined(struct uwb_rc *rc)
+{
+	return rc->beaconing != -1;
+}
+EXPORT_SYMBOL_GPL(uwb_bg_joined);
+
+/*
+ * Print beaconing state.
+ */
+static ssize_t uwb_rc_beacon_show(struct device *dev,
+				  struct device_attribute *attr, char *buf)
+{
+	struct uwb_dev *uwb_dev = to_uwb_dev(dev);
+	struct uwb_rc *rc = uwb_dev->rc;
+	ssize_t result;
+
+	mutex_lock(&rc->uwb_dev.mutex);
+	result = sprintf(buf, "%d\n", rc->beaconing);
+	mutex_unlock(&rc->uwb_dev.mutex);
+	return result;
+}
+
+/*
+ * Start beaconing on the specified channel, or stop beaconing.
+ *
+ * The BPST offset of when to start searching for a beacon group to
+ * join may be specified.
+ */
+static ssize_t uwb_rc_beacon_store(struct device *dev,
+				   struct device_attribute *attr,
+				   const char *buf, size_t size)
+{
+	struct uwb_dev *uwb_dev = to_uwb_dev(dev);
+	struct uwb_rc *rc = uwb_dev->rc;
+	int channel;
+	unsigned bpst_offset = 0;
+	ssize_t result = -EINVAL;
+
+	result = sscanf(buf, "%d %u\n", &channel, &bpst_offset);
+	if (result >= 1)
+		result = uwb_rc_beacon(rc, channel, bpst_offset);
+
+	return result < 0 ? result : size;
+}
+DEVICE_ATTR(beacon, S_IRUGO | S_IWUSR, uwb_rc_beacon_show, uwb_rc_beacon_store);