Use the PRLTX mailbox from the struct pdb_config

lib/src/policy_engine.c

 static enum policy_engine_state pe_sink_select_cap(struct pdb_config *cfg)
 {
     /* Transmit the request */
-    chMBPost(&pdb_prltx_mailbox, (msg_t) last_dpm_request, TIME_IMMEDIATE);
+    chMBPost(&cfg->prl.tx_mailbox, (msg_t) last_dpm_request, TIME_IMMEDIATE);
     chEvtSignal(cfg->prl.tx_thread, PDB_EVT_PRLTX_MSG_TX);
     eventmask_t evt = chEvtWaitAny(PDB_EVT_PE_TX_DONE | PDB_EVT_PE_TX_ERR
             | PDB_EVT_PE_RESET);
     get_source_cap->hdr = PD_MSGTYPE_GET_SOURCE_CAP | PD_DATAROLE_UFP
         | PD_SPECREV_2_0 | PD_POWERROLE_SINK | PD_NUMOBJ(0);
     /* Transmit the Get_Source_Cap */
-    chMBPost(&pdb_prltx_mailbox, (msg_t) get_source_cap, TIME_IMMEDIATE);
+    chMBPost(&cfg->prl.tx_mailbox, (msg_t) get_source_cap, TIME_IMMEDIATE);
     chEvtSignal(cfg->prl.tx_thread, PDB_EVT_PRLTX_MSG_TX);
     eventmask_t evt = chEvtWaitAny(PDB_EVT_PE_TX_DONE | PDB_EVT_PE_TX_ERR
             | PDB_EVT_PE_RESET);
     cfg->dpm.get_sink_capability(cfg, snk_cap);
 
     /* Transmit our capabilities */
-    chMBPost(&pdb_prltx_mailbox, (msg_t) snk_cap, TIME_IMMEDIATE);
+    chMBPost(&cfg->prl.tx_mailbox, (msg_t) snk_cap, TIME_IMMEDIATE);
     chEvtSignal(cfg->prl.tx_thread, PDB_EVT_PRLTX_MSG_TX);
     eventmask_t evt = chEvtWaitAny(PDB_EVT_PE_TX_DONE | PDB_EVT_PE_TX_ERR
             | PDB_EVT_PE_RESET);
     accept->hdr = PD_MSGTYPE_ACCEPT | PD_DATAROLE_UFP | PD_SPECREV_2_0
         | PD_POWERROLE_SINK | PD_NUMOBJ(0);
     /* Transmit the Accept */
-    chMBPost(&pdb_prltx_mailbox, (msg_t) accept, TIME_IMMEDIATE);
+    chMBPost(&cfg->prl.tx_mailbox, (msg_t) accept, TIME_IMMEDIATE);
     chEvtSignal(cfg->prl.tx_thread, PDB_EVT_PRLTX_MSG_TX);
     eventmask_t evt = chEvtWaitAny(PDB_EVT_PE_TX_DONE | PDB_EVT_PE_TX_ERR
             | PDB_EVT_PE_RESET);
     softrst->hdr = PD_MSGTYPE_SOFT_RESET | PD_DATAROLE_UFP | PD_SPECREV_2_0
         | PD_POWERROLE_SINK | PD_NUMOBJ(0);
     /* Transmit the soft reset */
-    chMBPost(&pdb_prltx_mailbox, (msg_t) softrst, TIME_IMMEDIATE);
+    chMBPost(&cfg->prl.tx_mailbox, (msg_t) softrst, TIME_IMMEDIATE);
     chEvtSignal(cfg->prl.tx_thread, PDB_EVT_PRLTX_MSG_TX);
     eventmask_t evt = chEvtWaitAny(PDB_EVT_PE_TX_DONE | PDB_EVT_PE_TX_ERR
             | PDB_EVT_PE_RESET);
         | PD_POWERROLE_SINK | PD_NUMOBJ(0);
 
     /* Transmit the message */
-    chMBPost(&pdb_prltx_mailbox, (msg_t) reject, TIME_IMMEDIATE);
+    chMBPost(&cfg->prl.tx_mailbox, (msg_t) reject, TIME_IMMEDIATE);
     chEvtSignal(cfg->prl.tx_thread, PDB_EVT_PRLTX_MSG_TX);
     eventmask_t evt = chEvtWaitAny(PDB_EVT_PE_TX_DONE | PDB_EVT_PE_TX_ERR
             | PDB_EVT_PE_RESET);

lib/src/protocol_tx.c

 #include "pd.h"
 
 
-/* Protocol layer TX thread mailbox */
-mailbox_t pdb_prltx_mailbox;
-
 /*
  * Protocol TX machine states
  *
  */
 static enum protocol_tx_state protocol_tx_wait_message(struct pdb_config *cfg)
 {
-    (void) cfg;
     /* Wait for an event */
     eventmask_t evt = chEvtWaitAny(PDB_EVT_PRLTX_RESET | PDB_EVT_PRLTX_DISCARD
             | PDB_EVT_PRLTX_MSG_TX);
     /* If the policy engine is trying to send a message */
     if (evt & PDB_EVT_PRLTX_MSG_TX) {
         /* Get the message */
-        chMBFetch(&pdb_prltx_mailbox, (msg_t *) &protocol_tx_message, TIME_IMMEDIATE);
+        chMBFetch(&cfg->prl.tx_mailbox, (msg_t *) &protocol_tx_message, TIME_IMMEDIATE);
         /* If it's a Soft_Reset, reset the TX layer first */
         if (PD_MSGTYPE_GET(protocol_tx_message) == PD_MSGTYPE_SOFT_RESET
                 && PD_NUMOBJ_GET(protocol_tx_message) == 0) {
     enum protocol_tx_state state = PRLTxPHYReset;
 
     /* Initialize the mailbox */
-    chMBObjectInit(&pdb_prltx_mailbox, cfg->prl._tx_mailbox_queue, PDB_MSG_POOL_SIZE);
+    chMBObjectInit(&cfg->prl.tx_mailbox, cfg->prl._tx_mailbox_queue, PDB_MSG_POOL_SIZE);
 
     while (true) {
         switch (state) {

lib/src/protocol_tx.h

 #define PDB_EVT_PRLTX_DISCARD EVENT_MASK(3)
 #define PDB_EVT_PRLTX_MSG_TX EVENT_MASK(4)
 
-/* Protocol layer TX thread mailbox */
-extern mailbox_t pdb_prltx_mailbox;
-
 /* The ID to be used in transmission */
 extern int8_t pdb_prltx_messageidcounter;