Changes between Version 4 and Version 5 of 802.11/wlan_exp/app_notes/tutorial_token_mac/CPU_HIGH

Timestamp:

Jul 8, 2015, 2:17:53 PM (9 years ago)

Author:

chunter

Comment:

--

802.11/wlan_exp/app_notes/tutorial_token_mac/CPU_HIGH

@@ -14 +14 @@
 
 == Specific Changes ==
+
+
+=== Code Common to CPU_HIGH and CPU_LOW ===
+Changes should be made to [browser:ReferenceDesigns/w3_802.11/c/wlan_mac_common/include/wlan_mac_ipc_util.h wlan_mac_ipc_util.h].
+
+---- 
+
+We need to define two new types of IPC messages between CPU_LOW and CPU_HIGH. The first, which we will call {{{TOKEN_NEW_RESERVATION}}}, will primarily be used by an AP when it decrees that a token reservation period now belongs to one of the devices on its network. The second, which we will call {{{TOKEN_END_RESERVATION}}}, will primarily be used by an AP's CPU_LOW project to indicate to the AP that the current reservation period has ended and it should move on to the next device in its association table. Add the following snippet of code to [browser:ReferenceDesigns/w3_802.11/c/wlan_mac_common/include/wlan_mac_ipc_util.h wlan_mac_ipc_util.h]:
+
+{{{
+#!c
+
+#define IPC_MBOX_TOKEN_NEW_RESERVATION  20
+#define IPC_MBOX_TOKEN_END_RESERVATION  21
+
+typedef struct{
+        u32 res_duration;
+        u8      addr[6];
+        u16 reserved;
+} ipc_token_new_reservation;
+
+typedef enum {TOKEN_DURATION_COMPLETE, TOKEN_TIMEOUT, TOKEN_OFFER_REJECTION} token_end_reservation_reason_t;
+
+typedef struct{
+        token_end_reservation_reason_t reason;
+        wlan_mac_low_tx_details low_tx_details;
+} ipc_token_end_reservation;
+}}}
+
+The values of 20 and 21 are arbitrary. The key part is that you choose numbers that do not overlap with any of the other definitions that are prepended by {{{IPC_MBOX_}}}. It is these definitions that the processors use to determine what type of IPC message is currently being received. Next, {{{ipc_token_new_reservation}}} and {{{ipc_token_end_reservation}}} are structs that we will use to more easily fill in and process IPC payloads.
+
+----
 
 === Access Point (AP) ===
@@ -117 +149 @@
 ----
 
-=== Code Common to CPU_HIGH and CPU_LOW ===
-Changes should be made to [browser:ReferenceDesigns/w3_802.11/c/wlan_mac_common/include/wlan_mac_ipc_util.h wlan_mac_ipc_util.h].
-
----- 
-
-We need to define two new types of IPC messages between CPU_LOW and CPU_HIGH. The first, which we will call {{{TOKEN_NEW_RESERVATION}}}, will primarily be used by an AP when it decrees that a token reservation period now belongs to one of the devices on its network. The second, which we will call {{{TOKEN_END_RESERVATION}}}, will primarily be used by an AP's CPU_LOW project to indicate to the AP that the current reservation period has ended and it should move on to the next device in its association table. Add the following snippet of code to [browser:ReferenceDesigns/w3_802.11/c/wlan_mac_common/include/wlan_mac_ipc_util.h wlan_mac_ipc_util.h]:
-
-{{{
-#!c
-
-#define IPC_MBOX_TOKEN_NEW_RESERVATION  20
-#define IPC_MBOX_TOKEN_END_RESERVATION  21
-
-typedef struct{
-        u32 res_duration;
-        u8      addr[6];
-        u16 reserved;
-} ipc_token_new_reservation;
-
-typedef enum {TOKEN_DURATION_COMPLETE, TOKEN_TIMEOUT, TOKEN_OFFER_REJECTION} token_end_reservation_reason_t;
-
-typedef struct{
-        token_end_reservation_reason_t reason;
-        wlan_mac_low_tx_details low_tx_details;
-} ipc_token_end_reservation;
-}}}
-
-The values of 20 and 21 are arbitrary. The key part is that you choose numbers that do not overlap with any of the other definitions that are prepended by {{{IPC_MBOX_}}}. It is these definitions that the processors use to determine what type of IPC message is currently being received. Next, {{{ipc_token_new_reservation}}} and {{{ipc_token_end_reservation}}} are structs that we will use to more easily fill in and process IPC payloads.
-
-----
-
 === MAC High Framework ===
 Changes should be made to [browser:ReferenceDesigns/w3_802.11/c/wlan_mac_high_framework/wlan_mac_high.c wlan_mac_high.c].
@@ -153 +154 @@
 ---- 
 
-The first thing we need to do 
+The first thing we need to do implement the callback structure that we assumed in our AP modifications. First, we should add a new top-level global to [browser:ReferenceDesigns/w3_802.11/c/wlan_mac_high_framework/wlan_mac_high.c wlan_mac_high.c] at the top of the file:
+
+{{{
+#!c
+
+volatile function_ptr_t      token_new_reservation_callback;
+}}}
+
+This variable will serve to hold the pointer to a function that should be called when the framework wants the AP to issue a new token reservation. For safety, we should explicitly set this function pointer to the nullCallback at boot so calling this function pointer does not crash the CPU. To do this, add the following line to {{{wlan_mac_high_init()}}}:
+
+{{{
+#!c
+
+token_new_reservation_callback = (function_ptr_t)nullCallback;
+}}}
+
+Finally, we should create a function that allows the AP code (or whatever other high-level project) assign the new callback. Add this function to the MAC High Framework:
+
+{{{
+#!c
+
+void wlan_mac_high_set_token_new_reservation_callback(function_ptr_t callback){
+        token_new_reservation_callback = callback;
+}
+}}}
+
+We have now implemented the {{{wlan_mac_high_set_token_new_reservation_callback()}}} function that we called in our AP modifications.
+
+----
+
+Finally, we need to actually call the {{{token_new_reservation_callback()}}} function pointer. We need to establish a contract with CPU_LOW. Specifically, we will assume that every time the AP sends down a {{{TOKEN_NEW_RESERVATION}}} IPC message to CPU_LOW, there will be a response of a {{{TOKEN_END_RESERVATION}}} IPC message at some point after that event. In other words, CPU_HIGH will not be responsible for determining when any given reservation period is over. We will assume (and will subsequently have to build) CPU_LOW will tell CPU_HIGH when a new token reservation period should be issued. As such, we just need to call {{{token_new_reservation_callback()}}} whenever we get a {{{TOKEN_END_RESERVATION}}} IPC message from CPU_LOW. This is an easy modification to make. In {{{wlan_mac_high_process_ipc_msg()}}}, there is a big switch statement that handled every type of IPC message ID. All we need to do as add a new case to this switch:
+
+{{{
+#!c
+
+                case IPC_MBOX_TOKEN_END_RESERVATION:
+                        token_new_reservation_callback();
+                break;
+}}}
+
+----
+
+
+