diff --git a/sys/cb_mux/Makefile b/sys/cb_mux/Makefile
new file mode 100644
index 0000000000000000000000000000000000000000..48422e909a47d7cd428d10fa73825060ccc8d8c2
--- /dev/null
+++ b/sys/cb_mux/Makefile
@@ -0,0 +1 @@
+include $(RIOTBASE)/Makefile.base
diff --git a/sys/cb_mux/cb_mux.c b/sys/cb_mux/cb_mux.c
new file mode 100644
index 0000000000000000000000000000000000000000..0a8164ebcf7f9de7b45164f1fe429d5e8eac053b
--- /dev/null
+++ b/sys/cb_mux/cb_mux.c
@@ -0,0 +1,124 @@
+/*
+ * Copyright (C) 2018 Acutam Automation, LLC
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup sys_cb_mux
+ * @{
+ *
+ * @file
+ * @brief cb_mux implementation
+ *
+ * @author Matthew Blue <matthew.blue.neuro@gmail.com>
+ * @}
+ */
+
+#include "cb_mux.h"
+#include "utlist.h"
+
+void cb_mux_add(cb_mux_t **head, cb_mux_t *entry)
+{
+ LL_APPEND(*head, entry);
+}
+
+void cb_mux_del(cb_mux_t **head, cb_mux_t *entry)
+{
+ LL_DELETE(*head, entry);
+}
+
+cb_mux_t *cb_mux_find_cbid(cb_mux_t *head, cb_mux_cbid_t cbid_val)
+{
+ cb_mux_t *entry;
+
+ LL_SEARCH_SCALAR(head, entry, cbid, cbid_val);
+
+ return entry;
+}
+
+cb_mux_t *cb_mux_find_low(cb_mux_t *head)
+{
+ cb_mux_t *entry;
+ cb_mux_t *entry_low = NULL;
+ cb_mux_cbid_t id = (cb_mux_cbid_t)(-1);
+
+ LL_FOREACH(head, entry) {
+ /* Entry does not have lower ID */
+ if (entry->cbid >= id) {
+ continue;
+ }
+
+ id = entry->cbid;
+ entry_low = entry;
+ }
+
+ return entry_low;
+}
+
+cb_mux_t *cb_mux_find_high(cb_mux_t *head)
+{
+ cb_mux_t *entry;
+ cb_mux_t *entry_high = NULL;
+ cb_mux_cbid_t id = 0;
+
+ LL_FOREACH(head, entry) {
+ /* Entry does not have higher ID */
+ if (entry->cbid <= id) {
+ continue;
+ }
+
+ id = entry->cbid;
+ entry_high = entry;
+ }
+
+ return entry_high;
+}
+
+cb_mux_cbid_t cb_mux_find_free_id(cb_mux_t *head)
+{
+ uint32_t free;
+ cb_mux_cbid_t block;
+ cb_mux_t *entry;
+ uint8_t num;
+
+ /* Search for free IDs in blocks of 32 IDs */
+ for (block = 0; block + 31 < (cb_mux_cbid_t)(-1); block += 32) {
+ /* Set all IDs in block to free */
+ free = 0;
+
+ LL_FOREACH(head, entry) {
+ /* cbid falls within this block */
+ if ((entry->cbid >= block) && (entry->cbid < block + 32)) {
+ /* Set cbid to taken */
+ free |= 1 << (entry->cbid & 0x1F);
+ }
+ }
+
+ /* At least one ID in block free */
+ if (~free) {
+ break;
+ }
+ }
+
+ /* Find which ID in block was free */
+ for (num = 0; num < 32; num++) {
+ if (~free & (1 << num)) {
+ return block | num;
+ }
+ }
+
+ /* No free IDs */
+ return (cb_mux_cbid_t)(-1);
+}
+
+void cb_mux_iter(cb_mux_t *head, cb_mux_iter_t func, void *arg)
+{
+ cb_mux_t *entry;
+
+ LL_FOREACH(head, entry) {
+ func(entry, arg);
+ }
+}
diff --git a/sys/include/cb_mux.h b/sys/include/cb_mux.h
new file mode 100644
index 0000000000000000000000000000000000000000..8f28223c105a287e70bcb44a31c17772681e4e0e
--- /dev/null
+++ b/sys/include/cb_mux.h
@@ -0,0 +1,143 @@
+/*
+ * Copyright (C) 2018 Acutam Automation, LLC
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @defgroup sys_cb_mux Callback multiplexer
+ * @ingroup sys
+ * @brief cb_mux provides utilities for storing, retrieving, and managing
+ * callback information in a singly linked list.
+ *
+ * If an API provides the ability to call multiple callbacks, cb_mux can
+ * simplify handling of an arbitrary number of callbacks by requiring memory
+ * for a cb_mux entry to be passed along with other arguments. The cb_mux entry
+ * is then attached to a list using cb_mux_add. The code implementing that API
+ * can manage the list using the various utility functions that cb_mux provides.
+ *
+ * @{
+ *
+ * @file
+ * @brief cb_mux interface definitions
+ *
+ * @author Matthew Blue <matthew.blue.neuro@gmail.com>
+ */
+
+#ifndef CB_MUX_H
+#define CB_MUX_H
+
+#include <stdint.h>
+
+/* For alternate cb_mux_cbid_t */
+#include "periph_cpu.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifndef HAVE_CB_MUX_CBID_T
+/**
+ * @brief cb_mux identifier type
+ */
+typedef unsigned int cb_mux_cbid_t;
+#endif
+
+/**
+ * @brief cb_mux callback type
+ */
+typedef void (*cb_mux_cb_t)(void *);
+
+/**
+ * @brief cb_mux list entry structure
+ */
+typedef struct cb_mux {
+ struct cb_mux *next; /**< next entry in the cb_mux list */
+ cb_mux_cbid_t cbid; /**< identifier for this callback */
+ void *info; /**< optional extra information */
+ cb_mux_cb_t cb; /**< callback function */
+ void *arg; /**< argument for callback function */
+} cb_mux_t;
+
+/**
+ * @brief cb_mux iterate function callback type for cb_mux_iter
+ */
+typedef void (*cb_mux_iter_t)(cb_mux_t *, void *);
+
+/**
+ * @brief Add a new entry to the end of a cb_mux list
+ *
+ * @param[in] head double pointer to first list entry
+ * @param[in] entry entry to add
+ */
+void cb_mux_add(cb_mux_t **head, cb_mux_t *entry);
+
+/**
+ * @brief Remove a entry from a cb_mux list
+ *
+ * @param[in] head double pointer to first list entry
+ * @param[in] entry entry to remove
+ */
+void cb_mux_del(cb_mux_t **head, cb_mux_t *entry);
+
+/**
+ * @brief Find an entry in the list by ID
+ *
+ * @param[in] head pointer to first list entry
+ * @param[in] cbid_val ID to find
+ *
+ * @return pointer to the list entry
+ */
+cb_mux_t *cb_mux_find_cbid(cb_mux_t *head, cb_mux_cbid_t cbid_val);
+
+/**
+ * @brief Find the entry with the lowest ID
+ *
+ * If there are multiple hits, this returns the oldest.
+ *
+ * @param[in] head pointer to first list entry
+ *
+ * @return pointer to the list entry
+ */
+cb_mux_t *cb_mux_find_low(cb_mux_t *head);
+
+/**
+ * @brief Find the entry with the highest ID
+ *
+ * If there are multiple hits, this returns the oldest.
+ *
+ * @param[in] head pointer to first list entry
+ *
+ * @return pointer to the list entry
+ */
+cb_mux_t *cb_mux_find_high(cb_mux_t *head);
+
+/**
+ * @brief Find the lowest unused ID
+ *
+ * Returns highest possible ID on failure
+ *
+ * @param[in] head pointer to first list entry
+ *
+ * @return lowest unused ID
+ */
+cb_mux_cbid_t cb_mux_find_free_id(cb_mux_t *head);
+
+/**
+ * @brief Run a function on every item in the cb_mux list
+ *
+ * @param[in] head pointer to first list entry
+ * @param[in] func function to run on each entry
+ * @param[in] arg argument for the function
+ */
+void cb_mux_iter(cb_mux_t *head, cb_mux_iter_t func, void *arg);
+
+#ifdef __cplusplus
+}
+#endif
+
+/** @} */
+
+#endif /* CB_MUX_H */
diff --git a/tests/cb_mux/Makefile b/tests/cb_mux/Makefile
new file mode 100644
index 0000000000000000000000000000000000000000..85812a0d9df5bab77d7e723b10eca1bd02ece86a
--- /dev/null
+++ b/tests/cb_mux/Makefile
@@ -0,0 +1,10 @@
+include ../Makefile.tests_common
+
+USEMODULE += cb_mux
+
+TEST_ON_CI_WHITELIST += all
+
+include $(RIOTBASE)/Makefile.include
+
+test:
+ ./tests/01-run.py
diff --git a/tests/cb_mux/main.c b/tests/cb_mux/main.c
new file mode 100644
index 0000000000000000000000000000000000000000..872834ed7b5710fd143f963d76bfff6ea1fcd992
--- /dev/null
+++ b/tests/cb_mux/main.c
@@ -0,0 +1,135 @@
+/*
+ * Copyright (C) 2018 Acutam Automation, LLC
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup tests
+ * @{
+ *
+ * @file
+ * @brief cb_mux test application
+ *
+ * @author Matthew Blue <matthew.blue.neuro@gmail.com>
+ * @}
+ */
+
+#include <stdio.h>
+
+#include "cb_mux.h"
+
+/* Head of cb_mux list */
+cb_mux_t *cb_mux_head;
+
+/* Flags for mux_iter */
+enum {
+ ITER_TEST = 1
+};
+
+/* Function to iterate over cb_mux list */
+void mux_iter(cb_mux_t *entry, void *arg)
+{
+ (void)arg;
+
+ entry->info = (void *)((uintptr_t)entry->info | (1 << ITER_TEST));
+}
+
+/* Test callback */
+void cb(void *arg)
+{
+ printf("Callback %u executed\n", (uint8_t)(uintptr_t)arg);
+}
+
+int main(void)
+{
+ cb_mux_t entries[5];
+ cb_mux_cbid_t num;
+ cb_mux_t *entry;
+
+ puts("cb_mux test routine");
+
+ for (num = 0; num < 5; num++) {
+ entries[num].cb = cb;
+ entries[num].arg = (void *)num;
+ entries[num].cbid = num;
+ }
+
+ puts("Test list addition, retrieval, execution of 5 CBs");
+
+ for (num = 0; num < 5; num++) {
+ cb_mux_add(&cb_mux_head, &(entries[num]));
+ }
+
+ for (num = 0; num < 5; num++) {
+ entry = cb_mux_find_cbid(cb_mux_head, num);
+
+ if (entry->cb == NULL) {
+ puts("[FAILED] Unexpected NULL pointer");
+ return 1;
+ }
+
+ entry->cb(entry->arg);
+ }
+
+ puts("Test list deletion of CB 0, 2, 4, execution of 1, 3");
+
+ cb_mux_del(&cb_mux_head, &(entries[0]));
+ cb_mux_del(&cb_mux_head, &(entries[2]));
+ cb_mux_del(&cb_mux_head, &(entries[4]));
+
+ for (num = 0; num < 5; num++) {
+ entry = cb_mux_find_cbid(cb_mux_head, num);
+
+ if (entry == NULL) {
+ continue;
+ }
+
+ entry->cb(entry->arg);
+ }
+
+ puts("Test execution of CB with lowest ID (1)");
+
+ entry = cb_mux_find_low(cb_mux_head);
+ if (entry->cb == NULL) {
+ puts("[FAILED] Unexpected NULL pointer");
+ return 1;
+ }
+ entry->cb(entry->arg);
+
+ puts("Test execution of CB with highest ID (3)");
+
+ entry = cb_mux_find_high(cb_mux_head);
+ if (entry->cb == NULL) {
+ puts("[FAILED] Unexpected NULL pointer");
+ return 1;
+ }
+ entry->cb(entry->arg);
+
+ puts("Re-adding list entries (0, 2, 4) by finding next free ID");
+
+ num = cb_mux_find_free_id(cb_mux_head);
+ while (num < 5) {
+ cb_mux_add(&cb_mux_head, &(entries[num]));
+
+ printf("Added entry %i\n", num);
+
+ num = cb_mux_find_free_id(cb_mux_head);
+ }
+
+ puts("Test iteration of a function over list");
+
+ cb_mux_iter(cb_mux_head, mux_iter, NULL);
+
+ for (num = 0; num < 5; num++) {
+ if ((uintptr_t)entries[num].info & (1 << ITER_TEST)) {
+ printf("Entry %i was updated correctly\n", num);
+ }
+ }
+
+ puts("Tests complete!");
+
+ return 0;
+}
diff --git a/tests/cb_mux/tests/01-run.py b/tests/cb_mux/tests/01-run.py
new file mode 100755
index 0000000000000000000000000000000000000000..d501e26601605e988f398fbe9d6b3f7bacb5e5e6
--- /dev/null
+++ b/tests/cb_mux/tests/01-run.py
@@ -0,0 +1,44 @@
+#!/usr/bin/env python3
+
+# Copyright (C) 2018 Acutam Automation, LLC
+#
+# This file is subject to the terms and conditions of the GNU Lesser
+# General Public License v2.1. See the file LICENSE in the top level
+# directory for more details.
+
+import os
+import sys
+
+
+def testfunc(child):
+ child.expect_exact("cb_mux test routine")
+ child.expect_exact("Test list addition, retrieval, execution of 5 CBs")
+ child.expect_exact("Callback 0 executed")
+ child.expect_exact("Callback 1 executed")
+ child.expect_exact("Callback 2 executed")
+ child.expect_exact("Callback 3 executed")
+ child.expect_exact("Callback 4 executed")
+ child.expect_exact("Test list deletion of CB 0, 2, 4, execution of 1, 3")
+ child.expect_exact("Callback 1 executed")
+ child.expect_exact("Callback 3 executed")
+ child.expect_exact("Test execution of CB with lowest ID (1)")
+ child.expect_exact("Callback 1 executed")
+ child.expect_exact("Test execution of CB with highest ID (3)")
+ child.expect_exact("Callback 3 executed")
+ child.expect_exact("Re-adding list entries (0, 2, 4) by finding next free ID")
+ child.expect_exact("Added entry 0")
+ child.expect_exact("Added entry 2")
+ child.expect_exact("Added entry 4")
+ child.expect_exact("Test iteration of a function over list")
+ child.expect_exact("Entry 0 was updated correctly")
+ child.expect_exact("Entry 1 was updated correctly")
+ child.expect_exact("Entry 2 was updated correctly")
+ child.expect_exact("Entry 3 was updated correctly")
+ child.expect_exact("Entry 4 was updated correctly")
+ child.expect_exact("Tests complete!")
+
+
+if __name__ == "__main__":
+ sys.path.append(os.path.join(os.environ['RIOTBASE'], 'dist/tools/testrunner'))
+ from testrunner import run
+ sys.exit(run(testfunc))
diff --git a/tests/cb_mux_bench/Makefile b/tests/cb_mux_bench/Makefile
new file mode 100644
index 0000000000000000000000000000000000000000..61b37720f2a84d916860a766ddc1c35b79d1f96c
--- /dev/null
+++ b/tests/cb_mux_bench/Makefile
@@ -0,0 +1,11 @@
+include ../Makefile.tests_common
+
+USEMODULE += cb_mux \
+ xtimer
+
+TEST_ON_CI_WHITELIST += all
+
+include $(RIOTBASE)/Makefile.include
+
+test:
+ ./tests/01-run.py
diff --git a/tests/cb_mux_bench/main.c b/tests/cb_mux_bench/main.c
new file mode 100644
index 0000000000000000000000000000000000000000..478d4f1657d20d2c863a941adee86a1721ac1f39
--- /dev/null
+++ b/tests/cb_mux_bench/main.c
@@ -0,0 +1,90 @@
+/*
+ * Copyright (C) 2018 Acutam Automation, LLC
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup tests
+ * @{
+ *
+ * @file
+ * @brief cb_mux benchmark application
+ *
+ * @author Matthew Blue <matthew.blue.neuro@gmail.com>
+ * @}
+ */
+
+#include <stdio.h>
+
+#include "cb_mux.h"
+#include "xtimer.h"
+
+/* Number of entries in the cb_mux list */
+#define NUM_ENTRIES (20U)
+
+/* Fail if us greater than threshold */
+#define FAIL_THRESH (200UL)
+
+/* Head of cb_mux list */
+cb_mux_t *cb_mux_head;
+
+/* cb_mux list entries */
+cb_mux_t entries[NUM_ENTRIES];
+
+/* Timing */
+unsigned long time_prev, time_curr;
+
+void cb(void *arg)
+{
+ (void)arg;
+ time_curr = xtimer_now_usec();
+}
+
+int main(void)
+{
+ unsigned long xtimer_delay, time_diff;
+ uint8_t num;
+ cb_mux_t *entry;
+
+ puts("cb_mux benchmark application");
+
+ /* Delay due to fetching timer with xtimer */
+ time_prev = xtimer_now_usec();
+ xtimer_delay = time_prev - xtimer_now_usec();
+
+ /* Test for worst case: finding last entry */
+ entries[NUM_ENTRIES - 1].cbid = 1;
+
+ printf("Populating cb_mux list with %u items\n", NUM_ENTRIES);
+
+ for (num = 0; num < NUM_ENTRIES; num++) {
+ entries[num].cb = cb;
+ cb_mux_add(&cb_mux_head, &(entries[num]));
+ }
+
+ puts("Finding the last list entry");
+
+ time_prev = xtimer_now_usec();
+
+ entry = cb_mux_find_cbid(cb_mux_head, 1);
+ entry->cb(entry->arg);
+
+ time_diff = time_curr - time_prev - xtimer_delay;
+
+ printf("List walk time: %lu us\n", time_diff);
+
+ if (time_diff > FAIL_THRESH) {
+ printf("Walk time greater than threshold of %lu us\n", FAIL_THRESH);
+ puts("[FAILURE]");
+ return 1;
+ }
+ else {
+ printf("Walk time less than threshold of %lu us\n", FAIL_THRESH);
+ puts("[SUCCESS]");
+ }
+
+ return 0;
+}
diff --git a/tests/cb_mux_bench/tests/01-run.py b/tests/cb_mux_bench/tests/01-run.py
new file mode 100755
index 0000000000000000000000000000000000000000..23896a9dfe4a0e1678d3bc492324d7a527a10f5a
--- /dev/null
+++ b/tests/cb_mux_bench/tests/01-run.py
@@ -0,0 +1,25 @@
+#!/usr/bin/env python3
+
+# Copyright (C) 2018 Acutam Automation, LLC
+#
+# This file is subject to the terms and conditions of the GNU Lesser
+# General Public License v2.1. See the file LICENSE in the top level
+# directory for more details.
+
+import os
+import sys
+
+
+def testfunc(child):
+ child.expect_exact("cb_mux benchmark application")
+ child.expect(u"Populating cb_mux list with \d+ items")
+ child.expect_exact("Finding the last list entry")
+ child.expect(u"List walk time: \d+ us")
+ child.expect(u"Walk time less than threshold of \d+ us")
+ child.expect_exact("[SUCCESS]")
+
+
+if __name__ == "__main__":
+ sys.path.append(os.path.join(os.environ['RIOTBASE'], 'dist/tools/testrunner'))
+ from testrunner import run
+ sys.exit(run(testfunc))