Correctly state via PD whether we can do USB comms

When running in Setup mode, the Sink is capable of USB communications.
Now it's honest about that in the Request and Sink_Capabilities
messages.

src/device_policy_manager.c

@@ -30,6 +30,8 @@
 
 bool pdb_dpm_led_pd_status = true;
 
+bool pdb_dpm_usb_comms = false;
+
 
 /* The current draw when the output is disabled */
 #define DPM_MIN_CURRENT PD_MA2PDI(100)
@@ -86,6 +88,9 @@ bool pdb_dpm_evaluate_capability(const union pd_msg *capabilities, union pd_msg
                         | PD_RDO_FV_CURRENT_SET(cfg->i)
                         | PD_RDO_NO_USB_SUSPEND | PD_RDO_OBJPOS_SET(i + 1);
                 }
+                if (pdb_dpm_usb_comms) {
+                    request->obj[0] |= PD_RDO_USB_COMMS;
+                }
 
                 /* Update requested voltage */
                 dpm_requested_voltage = cfg->v;
@@ -101,6 +106,9 @@ bool pdb_dpm_evaluate_capability(const union pd_msg *capabilities, union pd_msg
         | PD_RDO_FV_CURRENT_SET(DPM_MIN_CURRENT)
         | PD_RDO_NO_USB_SUSPEND | PD_RDO_CAP_MISMATCH
         | PD_RDO_OBJPOS_SET(1);
+    if (pdb_dpm_usb_comms) {
+        request->obj[0] |= PD_RDO_USB_COMMS;
+    }
 
     /* Update requested voltage */
     dpm_requested_voltage = PD_MV2PDV(5000);
@@ -140,6 +148,11 @@ void pdb_dpm_get_sink_capability(union pd_msg *cap)
         cap->obj[0] |= PD_PDO_SNK_FIXED_UNCONSTRAINED;
     }
 
+    /* Set the USB communications capable flag. */
+    if (pdb_dpm_usb_comms) {
+        cap->obj[0] |= PD_PDO_SNK_FIXED_USB_COMMS;
+    }
+
     /* Set the Sink_Capabilities message header */
     cap->hdr = PD_MSGTYPE_SINK_CAPABILITIES | PD_DATAROLE_UFP | PD_SPECREV_2_0
         | PD_POWERROLE_SINK | PD_NUMOBJ(numobj);

src/device_policy_manager.h

@@ -27,6 +27,9 @@
 /* Whether the DPM sets the LED to indicate the PD status */
 extern bool pdb_dpm_led_pd_status;
 
+/* Whether the device is capable of USB communications */
+extern bool pdb_dpm_usb_comms;
+
 
 /*
  * Create a Request message based on the given Source_Capabilities message.

src/main.c

@@ -90,8 +90,9 @@ static void start_pd(void)
  */
 static void setup(void)
 {
-    /* Set the DPM to not set the LED to show PD status */
+    /* Configure the DPM to play nice with the shell */
     pdb_dpm_led_pd_status = false;
+    pdb_dpm_usb_comms = true;
 
     /* Start the USB Power Delivery threads */
     start_pd();