From b4d1d0f9189df7d91991dcbeccee7fd867db2707 Mon Sep 17 00:00:00 2001
From: Peter Barker <pbarker@barker.dropbear.id.au>
Date: Tue, 20 Dec 2016 14:18:18 +1100
Subject: [PATCH] AP_Gripper: servo gripper not valid unless aux channel
 assigned

---
 libraries/AP_Gripper/AP_Gripper_Backend.h |  2 +-
 libraries/AP_Gripper/AP_Gripper_Servo.cpp | 11 +++++++++++
 libraries/AP_Gripper/AP_Gripper_Servo.h   |  3 +++
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/libraries/AP_Gripper/AP_Gripper_Backend.h b/libraries/AP_Gripper/AP_Gripper_Backend.h
index 06b68d51fb..30fb9f8a1d 100644
--- a/libraries/AP_Gripper/AP_Gripper_Backend.h
+++ b/libraries/AP_Gripper/AP_Gripper_Backend.h
@@ -35,7 +35,7 @@ public:
     virtual void release() = 0;
 
     // valid - returns true if the backend should be working
-    bool valid() const { return true; };
+    virtual bool valid() const { return true; };
 
     // released - returns true if currently in released position
     virtual bool released() const = 0;
diff --git a/libraries/AP_Gripper/AP_Gripper_Servo.cpp b/libraries/AP_Gripper/AP_Gripper_Servo.cpp
index 737a1037f9..3bc2752e61 100644
--- a/libraries/AP_Gripper/AP_Gripper_Servo.cpp
+++ b/libraries/AP_Gripper/AP_Gripper_Servo.cpp
@@ -55,3 +55,14 @@ bool AP_Gripper_Servo::grabbed() const
 
 // type-specific periodic updates:
 void AP_Gripper_Servo::update_gripper() { };
+
+bool AP_Gripper_Servo::valid() const
+{
+    if (!AP_Gripper_Backend::valid()) {
+        return false;
+    }
+    if (!RC_Channel_aux::function_assigned(RC_Channel_aux::k_gripper)) {
+        return false;
+    }
+    return true;
+}
diff --git a/libraries/AP_Gripper/AP_Gripper_Servo.h b/libraries/AP_Gripper/AP_Gripper_Servo.h
index 30ed1cde5e..1db0977208 100644
--- a/libraries/AP_Gripper/AP_Gripper_Servo.h
+++ b/libraries/AP_Gripper/AP_Gripper_Servo.h
@@ -36,6 +36,9 @@ public:
     // released - returns true if gripper in released state
     bool released() const override;
 
+    // valid - returns true if the backend should be working
+    bool valid() const;
+
 protected:
 
     // type-specific intiailisations: