Implement the typec_virtual PDO

The received Type-C Current advertisement is now kept in a global
variable which can be read by the command shell.  When there are no PD
capabilities but there is Type-C Current, the typec_virtual PDO is
reported as the one and only PDO.

src/device_policy_manager.c

@@ -25,7 +25,6 @@
 #include "led.h"
 #include "storage.h"
 #include "pd.h"
-#include "fusb302b.h"
 
 
 bool pdb_dpm_output_enabled = true;
@@ -33,6 +32,7 @@ bool pdb_dpm_led_pd_status = true;
 bool pdb_dpm_usb_comms = false;
 
 const union pd_msg *pdb_dpm_capabilities = NULL;
+enum fusb_typec_current pdb_dpm_typec_current = None;
 
 
 /* The current draw when the output is disabled */
@@ -200,21 +200,21 @@ bool pdb_dpm_evaluate_typec_current(void)
     /* We don't control the voltage anymore; it will always be 5 V. */
     dpm_requested_voltage = PD_MV2PDV(5000);
 
+    /* Get the present Type-C Current advertisement */
+    pdb_dpm_typec_current = fusb_get_typec_current();
+
     /* If we have no configuration or don't want 5 V, Type-C Current can't
      * possibly satisfy our needs */
     if (cfg == NULL || cfg->v != PD_MV2PDV(5000)) {
         return false;
     }
 
-    /* Get the present Type-C Current advertisement */
-    enum fusb_typec_current tcc = fusb_get_typec_current();
-
     /* If 1.5 A is available and we want no more than that, great. */
-    if (tcc == OnePointFiveAmps && cfg->i <= 150) {
+    if (pdb_dpm_typec_current == OnePointFiveAmps && cfg->i <= 150) {
         return true;
     }
     /* If 3 A is available and we want no more than that, that's great too. */
-    if (tcc == ThreePointZeroAmps && cfg->i <= 300) {
+    if (pdb_dpm_typec_current == ThreePointZeroAmps && cfg->i <= 300) {
         return true;
     }
     /* We're overly cautious if USB default current is available, since that

src/device_policy_manager.h

@@ -21,6 +21,7 @@
 
 #include <stdbool.h>
 
+#include "fusb302b.h"
 #include "messages.h"
 
 
@@ -36,6 +37,9 @@ extern bool pdb_dpm_usb_comms;
 /* The most recently received Source_Capabilities message */
 extern const union pd_msg *pdb_dpm_capabilities;
 
+/* The most recently received Type-C Current advertisement */
+extern enum fusb_typec_current pdb_dpm_typec_current;
+
 
 /*
  * Create a Request message based on the given Source_Capabilities message.  If

src/shell.c

@@ -351,10 +351,25 @@ static void cmd_get_source_cap(BaseSequentialStream *chp, int argc, char *argv[]
         return;
     }
 
-    /* If we haven't seen any Source_Capabilities yet, bail out now */
+    /* If we haven't seen any Source_Capabilities */
     if (pdb_dpm_capabilities == NULL) {
-        chprintf(chp, "No Source_Capabilities\r\n");
-        return;
+        /* Have we started reading Type-C Current advertisements? */
+        if (pdb_dpm_typec_current != None) {
+            /* Type-C Current is available, so report it */
+            chprintf(chp, "PDO 1: typec_virtual\r\n");
+            if (pdb_dpm_typec_current == Default) {
+                chprintf(chp, "\ti: 0.50 A\r\n");
+            } else if (pdb_dpm_typec_current == OnePointFiveAmps) {
+                chprintf(chp, "\ti: 1.50 A\r\n");
+            } else if (pdb_dpm_typec_current == ThreePointZeroAmps) {
+                chprintf(chp, "\ti: 3.00 A\r\n");
+            }
+            return;
+        } else {
+            /* No Type-C Current, so report no capabilities */
+            chprintf(chp, "No Source_Capabilities\r\n");
+            return;
+        }
     }
 
     /* Print all the PDOs */