From e7fac9f661042e8ba19fd98a592f3c9b526b29d2 Mon Sep 17 00:00:00 2001
From: Jose Alamos <jose@alamos.cc>
Date: Wed, 29 Sep 2021 16:52:58 +0200
Subject: [PATCH 1/8] net/gnrc_netif: add return values to init

---
 pkg/nimble/netif/nimble_netif.c               |  4 ++-
 sys/include/net/gnrc/netif.h                  | 25 +++++++++++--------
 sys/net/gnrc/link_layer/gomach/gomach.c       |  6 +++--
 sys/net/gnrc/link_layer/lwmac/lwmac.c         |  6 +++--
 sys/net/gnrc/netif/gnrc_netif.c               |  3 ++-
 .../gnrc/netif/lorawan/gnrc_netif_lorawan.c   |  6 +++--
 tests/gnrc_netif/main.c                       |  6 +++--
 7 files changed, 36 insertions(+), 20 deletions(-)

diff --git a/pkg/nimble/netif/nimble_netif.c b/pkg/nimble/netif/nimble_netif.c
index 0a6d196814c6..38a1eb33d016 100644
--- a/pkg/nimble/netif/nimble_netif.c
+++ b/pkg/nimble/netif/nimble_netif.c
@@ -79,7 +79,7 @@ static void _notify(int handle, nimble_netif_event_t event, uint8_t *addr)
     }
 }
 
-static void _netif_init(gnrc_netif_t *netif)
+static int _netif_init(gnrc_netif_t *netif)
 {
     (void)netif;
 
@@ -92,6 +92,8 @@ static void _netif_init(gnrc_netif_t *netif)
      * of this */
     _netif.sixlo.max_frag_size = 0;
 #endif  /* IS_USED(MODULE_GNRC_NETIF_6LO) */
+
+    return 0;
 }
 
 static int _send_pkt(nimble_netif_conn_t *conn, gnrc_pktsnip_t *pkt)
diff --git a/sys/include/net/gnrc/netif.h b/sys/include/net/gnrc/netif.h
index 6bfc214fddf9..2a3b515a48a4 100644
--- a/sys/include/net/gnrc/netif.h
+++ b/sys/include/net/gnrc/netif.h
@@ -194,21 +194,26 @@ typedef struct {
  */
 struct gnrc_netif_ops {
     /**
-     * @brief   Initializes network interface beyond the default settings
+     * @brief   Initializes network interface.
      *
      * @pre `netif != NULL`
      *
      * @param[in] netif The network interface.
      *
-     * This is called after the network device's initial configuration, right
-     * before the interface's thread starts receiving messages. It is not
-     * necessary to lock the interface's mutex gnrc_netif_t::mutex, since it is
-     * already locked. Set to @ref gnrc_netif_default_init() if you do not need
-     * any special initialization. If you do need special initialization, it is
-     * recommended to call @ref gnrc_netif_default_init() at the start of the
-     * custom initialization function set here.
+     * This function should init the device driver or MAC underlying MAC layer.
+     * This is called right before the interface's thread starts receiving
+     * messages. It is not necessary to lock the interface's mutex
+     * gnrc_netif_t::mutex, since it is already locked. Set to @ref
+     * gnrc_netif_default_init() if you do not need any special initialization.
+     * If you do need special initialization, it is recommended to call @ref
+     * gnrc_netif_default_init() at the start of the custom initialization
+     * function set here.
+     *
+     * @return 0 if the initialization of the device or MAC layer was
+     * successful
+     * @return negative errno on error.
      */
-    void (*init)(gnrc_netif_t *netif);
+    int (*init)(gnrc_netif_t *netif);
 
     /**
      * @brief   Send a @ref net_gnrc_pkt "packet" over the network interface
@@ -537,7 +542,7 @@ static inline int gnrc_netif_ipv6_group_leave(const gnrc_netif_t *netif,
  *
  * @param[in] netif     The network interface.
  */
-void gnrc_netif_default_init(gnrc_netif_t *netif);
+int gnrc_netif_default_init(gnrc_netif_t *netif);
 
 /**
  * @brief   Default operation for gnrc_netif_ops_t::get()
diff --git a/sys/net/gnrc/link_layer/gomach/gomach.c b/sys/net/gnrc/link_layer/gomach/gomach.c
index e16ec867f6f3..1c119e8e3017 100644
--- a/sys/net/gnrc/link_layer/gomach/gomach.c
+++ b/sys/net/gnrc/link_layer/gomach/gomach.c
@@ -55,7 +55,7 @@
  */
 static kernel_pid_t gomach_pid;
 
-static void _gomach_init(gnrc_netif_t *netif);
+static int _gomach_init(gnrc_netif_t *netif);
 static int _send(gnrc_netif_t *netif, gnrc_pktsnip_t *pkt);
 static gnrc_pktsnip_t *_recv(gnrc_netif_t *netif);
 static void _gomach_msg_handler(gnrc_netif_t *netif, msg_t *msg);
@@ -2115,7 +2115,7 @@ static void _gomach_event_cb(netdev_t *dev, netdev_event_t event)
     }
 }
 
-static void _gomach_init(gnrc_netif_t *netif)
+static int _gomach_init(gnrc_netif_t *netif)
 {
     netdev_t *dev;
 
@@ -2216,4 +2216,6 @@ static void _gomach_init(gnrc_netif_t *netif)
         gnrc_gomach_set_update(netif, false);
         gomach_update(netif);
     }
+
+    return 0;
 }
diff --git a/sys/net/gnrc/link_layer/lwmac/lwmac.c b/sys/net/gnrc/link_layer/lwmac/lwmac.c
index 1f6db582121d..e4de75b6ef19 100644
--- a/sys/net/gnrc/link_layer/lwmac/lwmac.c
+++ b/sys/net/gnrc/link_layer/lwmac/lwmac.c
@@ -63,7 +63,7 @@ static void rtt_cb(void *arg);
 static void lwmac_set_state(gnrc_netif_t *netif, gnrc_lwmac_state_t newstate);
 static void lwmac_schedule_update(gnrc_netif_t *netif);
 static void rtt_handler(uint32_t event, gnrc_netif_t *netif);
-static void _lwmac_init(gnrc_netif_t *netif);
+static int _lwmac_init(gnrc_netif_t *netif);
 static int _send(gnrc_netif_t *netif, gnrc_pktsnip_t *pkt);
 static gnrc_pktsnip_t *_recv(gnrc_netif_t *netif);
 static void _lwmac_msg_handler(gnrc_netif_t *netif, msg_t *msg);
@@ -939,7 +939,7 @@ static void _lwmac_msg_handler(gnrc_netif_t *netif, msg_t *msg)
     }
 }
 
-static void _lwmac_init(gnrc_netif_t *netif)
+static int _lwmac_init(gnrc_netif_t *netif)
 {
     netdev_t *dev;
 
@@ -984,4 +984,6 @@ static void _lwmac_init(gnrc_netif_t *netif)
     netif->mac.prot.lwmac.awake_duration_sum_ticks = 0;
     netif->mac.prot.lwmac.lwmac_info |= GNRC_LWMAC_RADIO_IS_ON;
 #endif
+
+    return 0;
 }
diff --git a/sys/net/gnrc/netif/gnrc_netif.c b/sys/net/gnrc/netif/gnrc_netif.c
index c0f1dd8bc88b..f39752fc3ba7 100644
--- a/sys/net/gnrc/netif/gnrc_netif.c
+++ b/sys/net/gnrc/netif/gnrc_netif.c
@@ -1577,7 +1577,7 @@ static void _test_options(gnrc_netif_t *netif)
 }
 #endif /* DEVELHELP */
 
-void gnrc_netif_default_init(gnrc_netif_t *netif)
+int gnrc_netif_default_init(gnrc_netif_t *netif)
 {
     _init_from_device(netif);
 #ifdef DEVELHELP
@@ -1590,6 +1590,7 @@ void gnrc_netif_default_init(gnrc_netif_t *netif)
 #ifdef MODULE_GNRC_IPV6_NIB
     gnrc_ipv6_nib_init_iface(netif);
 #endif
+    return 0;
 }
 
 static void _send(gnrc_netif_t *netif, gnrc_pktsnip_t *pkt, bool push_back);
diff --git a/sys/net/gnrc/netif/lorawan/gnrc_netif_lorawan.c b/sys/net/gnrc/netif/lorawan/gnrc_netif_lorawan.c
index 17cca566a7a9..33314fe8374a 100644
--- a/sys/net/gnrc/netif/lorawan/gnrc_netif_lorawan.c
+++ b/sys/net/gnrc/netif/lorawan/gnrc_netif_lorawan.c
@@ -48,7 +48,7 @@ static gnrc_pktsnip_t *_recv(gnrc_netif_t *netif);
 static void _msg_handler(gnrc_netif_t *netif, msg_t *msg);
 static int _get(gnrc_netif_t *netif, gnrc_netapi_opt_t *opt);
 static int _set(gnrc_netif_t *netif, const gnrc_netapi_opt_t *opt);
-static void _init(gnrc_netif_t *netif);
+static int _init(gnrc_netif_t *netif);
 
 static const gnrc_netif_ops_t lorawan_ops = {
     .init = _init,
@@ -252,7 +252,7 @@ netdev_t *gnrc_lorawan_get_netdev(gnrc_lorawan_t *mac)
     return netif->dev;
 }
 
-static void _init(gnrc_netif_t *netif)
+static int _init(gnrc_netif_t *netif)
 {
     gnrc_netif_default_init(netif);
     netif->dev->event_callback = _driver_cb;
@@ -279,6 +279,8 @@ static void _init(gnrc_netif_t *netif)
     ztimer_set_msg(ZTIMER_MSEC, &netif->lorawan.backoff_timer,
                    GNRC_LORAWAN_BACKOFF_WINDOW_TICK / 1000,
                    &backoff_msg, thread_getpid());
+
+    return 0;
 }
 
 int gnrc_netif_lorawan_create(gnrc_netif_t *netif, char *stack, int stacksize,
diff --git a/tests/gnrc_netif/main.c b/tests/gnrc_netif/main.c
index 9a72758e31f1..120fb8919324 100644
--- a/tests/gnrc_netif/main.c
+++ b/tests/gnrc_netif/main.c
@@ -55,7 +55,7 @@ static bool init_called = false;
 static uint8_t ethernet_groups[ETHERNET_GROUPS_MAX][ETHERNET_ADDR_LEN];
 static BITFIELD(ethernet_groups_set, ETHERNET_GROUPS_MAX);
 
-static inline void _test_init(gnrc_netif_t *netif);
+static inline int _test_init(gnrc_netif_t *netif);
 static inline int _mock_netif_send(gnrc_netif_t *netif, gnrc_pktsnip_t *pkt);
 static inline gnrc_pktsnip_t *_mock_netif_recv(gnrc_netif_t * netif);
 static int _get_netdev_address(netdev_t *dev, void *value, size_t max_len);
@@ -113,11 +113,13 @@ static void _set_up(void)
     while (msg_try_receive(&msg) > 0) {}
 }
 
-static inline void _test_init(gnrc_netif_t *netif)
+static inline int _test_init(gnrc_netif_t *netif)
 {
     (void)netif;
     gnrc_netif_default_init(netif);
     init_called = true;
+
+    return 0;
 }
 
 static void test_creation(void)

From 415704fa76971a51960eb29d9f7e52c5bdacd78c Mon Sep 17 00:00:00 2001
From: Jose Alamos <jose@alamos.cc>
Date: Thu, 30 Sep 2021 10:44:57 +0200
Subject: [PATCH 2/8] net/gnrc_netif: move netdev init code to ops->init

---
 sys/net/gnrc/netif/gnrc_netif.c | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/sys/net/gnrc/netif/gnrc_netif.c b/sys/net/gnrc/netif/gnrc_netif.c
index f39752fc3ba7..ff420bdad25e 100644
--- a/sys/net/gnrc/netif/gnrc_netif.c
+++ b/sys/net/gnrc/netif/gnrc_netif.c
@@ -1579,6 +1579,16 @@ static void _test_options(gnrc_netif_t *netif)
 
 int gnrc_netif_default_init(gnrc_netif_t *netif)
 {
+    netdev_t *dev = netif->dev;
+    /* register the event callback with the device driver */
+    dev->event_callback = _event_cb;
+    dev->context = netif;
+    int res = dev->driver->init(dev);
+    if (res < 0) {
+        return res;
+    }
+    netif_register(&netif->netif);
+    _check_netdev_capabilities(dev);
     _init_from_device(netif);
 #ifdef DEVELHELP
     _test_options(netif);
@@ -1829,7 +1839,6 @@ static void *_gnrc_netif_thread(void *args)
     DEBUG("gnrc_netif: starting thread %i\n", thread_getpid());
     netif = ctx->netif;
     gnrc_netif_acquire(netif);
-    dev = netif->dev;
     netif->pid = thread_getpid();
 
 #if IS_USED(MODULE_GNRC_NETIF_EVENTS)
@@ -1840,20 +1849,15 @@ static void *_gnrc_netif_thread(void *args)
 
     /* setup the link-layer's message queue */
     msg_init_queue(msg_queue, GNRC_NETIF_MSG_QUEUE_SIZE);
-    /* register the event callback with the device driver */
-    dev->event_callback = _event_cb;
-    dev->context = netif;
     /* initialize low-level driver */
-    ctx->result = dev->driver->init(dev);
+    ctx->result = netif->ops->init(netif);
     /* signal that driver init is done */
     mutex_unlock(&ctx->init_done);
     if (ctx->result < 0) {
-        LOG_ERROR("gnrc_netif: netdev init failed: %d\n", ctx->result);
+        LOG_ERROR("gnrc_netif: init failed: %d\n", ctx->result);
         return NULL;
     }
-    netif_register(&netif->netif);
-    _check_netdev_capabilities(dev);
-    netif->ops->init(netif);
+    dev = netif->dev;
 #if DEVELHELP
     assert(options_tested);
 #endif

From 49527fc9943821f0370dfbdfdf58fc6fd7f3988e Mon Sep 17 00:00:00 2001
From: Jose Alamos <jose@alamos.cc>
Date: Thu, 30 Sep 2021 10:46:58 +0200
Subject: [PATCH 3/8] pkg/nimble/netif: adapt ops->init to handle driver
 initialization

---
 pkg/nimble/netif/nimble_netif.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/pkg/nimble/netif/nimble_netif.c b/pkg/nimble/netif/nimble_netif.c
index 38a1eb33d016..ab307bccb1d8 100644
--- a/pkg/nimble/netif/nimble_netif.c
+++ b/pkg/nimble/netif/nimble_netif.c
@@ -83,7 +83,11 @@ static int _netif_init(gnrc_netif_t *netif)
 {
     (void)netif;
 
-    gnrc_netif_default_init(netif);
+    int res = gnrc_netif_default_init(netif);
+    if (res < 0) {
+        return res;
+    }
+
     /* save the threads context pointer, so we can set its flags */
     _netif_thread = thread_get_active();
 
@@ -92,8 +96,9 @@ static int _netif_init(gnrc_netif_t *netif)
      * of this */
     _netif.sixlo.max_frag_size = 0;
 #endif  /* IS_USED(MODULE_GNRC_NETIF_6LO) */
+    res = 0;
 
-    return 0;
+    return res;
 }
 
 static int _send_pkt(nimble_netif_conn_t *conn, gnrc_pktsnip_t *pkt)

From 298f16fee786f798bf77de7f3f25092b3b784d6f Mon Sep 17 00:00:00 2001
From: Jose Alamos <jose@alamos.cc>
Date: Thu, 30 Sep 2021 10:47:26 +0200
Subject: [PATCH 4/8] net/gomach: adapt ops->init to handle driver
 initialization

---
 sys/net/gnrc/link_layer/gomach/gomach.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/sys/net/gnrc/link_layer/gomach/gomach.c b/sys/net/gnrc/link_layer/gomach/gomach.c
index 1c119e8e3017..cf2364a2c297 100644
--- a/sys/net/gnrc/link_layer/gomach/gomach.c
+++ b/sys/net/gnrc/link_layer/gomach/gomach.c
@@ -2119,7 +2119,11 @@ static int _gomach_init(gnrc_netif_t *netif)
 {
     netdev_t *dev;
 
-    gnrc_netif_default_init(netif);
+    int res = gnrc_netif_default_init(netif);
+    if (res < 0) {
+        return res;
+    }
+
     dev = netif->dev;
     dev->event_callback = _gomach_event_cb;
 

From 08ec9693cd02879cffcd0dec273e03a03de7b725 Mon Sep 17 00:00:00 2001
From: Jose Alamos <jose@alamos.cc>
Date: Thu, 30 Sep 2021 10:47:42 +0200
Subject: [PATCH 5/8] net/lwmac: adapt ops->init to handle driver
 initialization

---
 sys/net/gnrc/link_layer/lwmac/lwmac.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/sys/net/gnrc/link_layer/lwmac/lwmac.c b/sys/net/gnrc/link_layer/lwmac/lwmac.c
index e4de75b6ef19..cf5876a392ab 100644
--- a/sys/net/gnrc/link_layer/lwmac/lwmac.c
+++ b/sys/net/gnrc/link_layer/lwmac/lwmac.c
@@ -943,7 +943,12 @@ static int _lwmac_init(gnrc_netif_t *netif)
 {
     netdev_t *dev;
 
-    gnrc_netif_default_init(netif);
+    int res = gnrc_netif_default_init(netif);
+
+    if (res < 0) {
+        return res;
+    }
+
     dev = netif->dev;
     dev->event_callback = _lwmac_event_cb;
 
@@ -985,5 +990,5 @@ static int _lwmac_init(gnrc_netif_t *netif)
     netif->mac.prot.lwmac.lwmac_info |= GNRC_LWMAC_RADIO_IS_ON;
 #endif
 
-    return 0;
+    return res;
 }

From 5f46ab72e07257ea2136141b0aa024b32403bab3 Mon Sep 17 00:00:00 2001
From: Jose Alamos <jose@alamos.cc>
Date: Thu, 30 Sep 2021 10:47:56 +0200
Subject: [PATCH 6/8] net/gnrc/lorawan: adapt ops->init to handle driver
 initialization

---
 sys/net/gnrc/netif/lorawan/gnrc_netif_lorawan.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/sys/net/gnrc/netif/lorawan/gnrc_netif_lorawan.c b/sys/net/gnrc/netif/lorawan/gnrc_netif_lorawan.c
index 33314fe8374a..0bc1d1d9f9d0 100644
--- a/sys/net/gnrc/netif/lorawan/gnrc_netif_lorawan.c
+++ b/sys/net/gnrc/netif/lorawan/gnrc_netif_lorawan.c
@@ -254,7 +254,12 @@ netdev_t *gnrc_lorawan_get_netdev(gnrc_lorawan_t *mac)
 
 static int _init(gnrc_netif_t *netif)
 {
-    gnrc_netif_default_init(netif);
+    int res = gnrc_netif_default_init(netif);
+
+    if (res < 0) {
+        return res;
+    }
+
     netif->dev->event_callback = _driver_cb;
     _reset(netif);
 
@@ -280,7 +285,7 @@ static int _init(gnrc_netif_t *netif)
                    GNRC_LORAWAN_BACKOFF_WINDOW_TICK / 1000,
                    &backoff_msg, thread_getpid());
 
-    return 0;
+    return res;
 }
 
 int gnrc_netif_lorawan_create(gnrc_netif_t *netif, char *stack, int stacksize,

From eb23813467561e1936f3abfcd7e6e929c6116166 Mon Sep 17 00:00:00 2001
From: Jose Alamos <jose@alamos.cc>
Date: Thu, 30 Sep 2021 10:48:52 +0200
Subject: [PATCH 7/8] tests/gnrc_netif: adapt ops->init to handle driver
 initialization

---
 tests/gnrc_netif/main.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/tests/gnrc_netif/main.c b/tests/gnrc_netif/main.c
index 120fb8919324..96f47b7f159b 100644
--- a/tests/gnrc_netif/main.c
+++ b/tests/gnrc_netif/main.c
@@ -116,7 +116,12 @@ static void _set_up(void)
 static inline int _test_init(gnrc_netif_t *netif)
 {
     (void)netif;
-    gnrc_netif_default_init(netif);
+    int res = gnrc_netif_default_init(netif);
+
+    if (res < 0) {
+        return res;
+    }
+
     init_called = true;
 
     return 0;

From e40f97c4daf81e713ec2ca5f5cdd177f84224cd1 Mon Sep 17 00:00:00 2001
From: Jose Alamos <jose@alamos.cc>
Date: Mon, 22 Nov 2021 11:03:40 +0100
Subject: [PATCH 8/8] net/gnrc/netif: move interface registration to init
 function

---
 sys/include/net/gnrc/netif.h | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/sys/include/net/gnrc/netif.h b/sys/include/net/gnrc/netif.h
index 2a3b515a48a4..7b5ccbb2127d 100644
--- a/sys/include/net/gnrc/netif.h
+++ b/sys/include/net/gnrc/netif.h
@@ -194,7 +194,7 @@ typedef struct {
  */
 struct gnrc_netif_ops {
     /**
-     * @brief   Initializes network interface.
+     * @brief   Initializes and registers network interface.
      *
      * @pre `netif != NULL`
      *
@@ -207,7 +207,8 @@ struct gnrc_netif_ops {
      * gnrc_netif_default_init() if you do not need any special initialization.
      * If you do need special initialization, it is recommended to call @ref
      * gnrc_netif_default_init() at the start of the custom initialization
-     * function set here.
+     * function set here. This function MUST call @ref netif_register if the
+     * initialization is successful.
      *
      * @return 0 if the initialization of the device or MAC layer was
      * successful
@@ -538,7 +539,8 @@ static inline int gnrc_netif_ipv6_group_leave(const gnrc_netif_t *netif,
 /**
  * @brief   Default operation for gnrc_netif_ops_t::init()
  *
- * @note    Can also be used to be called *before* a custom operation.
+ * @note    Can also be used to be called *before* a custom operation. This
+ *          function calls @ref netif_register internally.
  *
  * @param[in] netif     The network interface.
  */