Changes between Version 7 and Version 8 of 802.11/wlan_exp/Extending

Timestamp:

Dec 14, 2015, 9:47:24 PM (8 years ago)

Author:

murphpo

Comment:

--

802.11/wlan_exp/Extending

@@ -47 +47 @@
 The 802.11 MAC code running on the WARP node handles user commands at two levels.
 
-If the command behavior is common to all MAC applications, the command is handled in the {{{process_user_cmd()}}} function in {{{wlan_exp_user.c}}}. You should modify {{{process_user_cmd()}}} to handle any new framework-level commands required for your application. Any command IDs not hanlded in {{{process_user_cmd()}}} will be passed through to the MAC application.
+If the command behavior is common to all MAC applications, the command is handled in the {{{process_user_cmd()}}} function in {{{wlan_exp_user.c}}}. You should modify {{{process_user_cmd()}}} to handle any new framework-level commands required for your application. Any command IDs not handled in {{{process_user_cmd()}}} will be passed through to the MAC application.
 
 If a command behavior depends on the upper-level MAC application, the command is handled in the {{{wlan_exp_process_user_cmd()}}} callback function in the top-level MAC. You should modify the {{{wlan_exp_process_user_cmd()}}} function in the {{{wlan_mac_ap.c}}}, {{{wlan_mac_sta.c}}} and {{{wlan_mac_ibss.c}}} files to implement any MAC-specific command behaviors.
@@ -58 +58 @@
 
 The wlan_exp framework will encapsulate the command response payload in an Ethernet fame and return it to the calling Python script for processing.
+
+'''Interrupt Safety'''[[BR]]
+The {{{process_user_cmd()}}} and {{{wlan_exp_process_user_cmd()}}} functions executed outside the context of an interrupt service routine. As a result these functions may be interrupted at any time. Almost all processing in CPU High occurs in ISR contexts, including all processing of wireless and Ethernet Tx/Rx. If your command handler accesses or modifies data structures that might be modified in one of the upper-level MAC's interrupt service routines, you must take precautions to avoid bad states.
+
+The easiest way to protect a command handler from bad states due to unexpected interrupts is to disable interrupts during execution of the handler. 
+
+{{{#!c
+interrupt_state_t curr_interrupt_state;
+
+//Record the current interrupt enable state, then disable all interrupts
+curr_interrupt_state = wlan_mac_high_interrupt_stop();
+
+/*
+* Do any interrupt-sensitive processing here
+*/
+
+//Restore the interrupt enable state
+wlan_mac_high_interrupt_restore_state(curr_interrupt_state);
+}}}
+
+
 
 '''TODO:'''