HAL_Linux: implement I2C bus masks

libraries/AP_HAL_Linux/I2CDevice.cpp

@@ -417,4 +417,28 @@ void I2CDeviceManager::teardown()
     }
 }
 
+/*
+  get mask of bus numbers for all configured I2C buses
+*/
+uint32_t I2CDeviceManager::get_bus_mask(void) const
+{
+    return HAL_LINUX_I2C_BUS_MASK;
+}
+
+/*
+  get mask of bus numbers for all configured internal I2C buses
+*/
+uint32_t I2CDeviceManager::get_bus_mask_internal(void) const
+{
+    return HAL_LINUX_I2C_INTERNAL_BUS_MASK;
+}
+
+/*
+  get mask of bus numbers for all configured external I2C buses
+*/
+uint32_t I2CDeviceManager::get_bus_mask_external(void) const
+{
+    return HAL_LINUX_I2C_EXTERNAL_BUS_MASK;
+}
+    
 }

libraries/AP_HAL_Linux/I2CDevice.h

@@ -110,6 +110,21 @@ public:
      */
     void teardown();
 
+    /*
+      get mask of bus numbers for all configured I2C buses
+     */
+    uint32_t get_bus_mask(void) const override;
+
+    /*
+      get mask of bus numbers for all configured external I2C buses
+     */
+    uint32_t get_bus_mask_external(void) const override;
+
+    /*
+      get mask of bus numbers for all configured internal I2C buses
+     */
+    uint32_t get_bus_mask_internal(void) const override;
+    
 protected:
     void _unregister(I2CBus &b);
     AP_HAL::OwnPtr<AP_HAL::I2CDevice> _create_device(I2CBus &b, uint8_t address) const;