AP_HAL_Linux: remove pointless attach_interrupt override

libraries/AP_HAL_Linux/GPIO_BBB.cpp

@@ -112,14 +112,6 @@ AP_HAL::DigitalSource* GPIO_BBB::channel(uint16_t n) {
     return new DigitalSource(n);
 }
 
-/* Interrupt interface: */
-bool GPIO_BBB::attach_interrupt(uint8_t interrupt_num,
-                                irq_handler_fn_t fn,
-                                INTERRUPT_TRIGGER_TYPE mode)
-{
-    return true;
-}
-
 bool GPIO_BBB::usb_connected(void)
 {
     return false;

libraries/AP_HAL_Linux/GPIO_BBB.h

@@ -129,11 +129,6 @@ public:
     /* Alternative interface: */
     AP_HAL::DigitalSource* channel(uint16_t n);
 
-    /* Interrupt interface: */
-    bool    attach_interrupt(uint8_t interrupt_num,
-                             irq_handler_fn_t fn,
-                             INTERRUPT_TRIGGER_TYPE mode) override;
-
     /* return true if USB cable is connected */
     bool    usb_connected(void);
 };

libraries/AP_HAL_Linux/GPIO_RPI.cpp

@@ -121,14 +121,6 @@ AP_HAL::DigitalSource* GPIO_RPI::channel(uint16_t n)
     return new DigitalSource(n);
 }
 
-/* Interrupt interface: */
-bool GPIO_RPI::attach_interrupt(uint8_t interrupt_num,
-                                irq_handler_fn_t fn,
-                                INTERRUPT_TRIGGER_TYPE mode)
-{
-    return true;
-}
-
 bool GPIO_RPI::usb_connected(void)
 {
     return false;

libraries/AP_HAL_Linux/GPIO_RPI.h

@@ -56,11 +56,6 @@ public:
     /* Alternative interface: */
     AP_HAL::DigitalSource* channel(uint16_t n);
 
-    /* Interrupt interface: */
-    bool    attach_interrupt(uint8_t interrupt_num,
-                             irq_handler_fn_t fn,
-                             INTERRUPT_TRIGGER_TYPE mode);
-
     /* return true if USB cable is connected */
     bool    usb_connected(void);
 

libraries/AP_HAL_Linux/GPIO_Sysfs.cpp

@@ -188,13 +188,6 @@ AP_HAL::DigitalSource* GPIO_Sysfs::channel(uint16_t vpin)
     return new DigitalSource_Sysfs(pin, value_fd);
 }
 
-bool GPIO_Sysfs::attach_interrupt(uint8_t interrupt_num,
-                                  irq_handler_fn_t p,
-                                  INTERRUPT_TRIGGER_TYPE mode)
-{
-    return false;
-}
-
 bool GPIO_Sysfs::usb_connected(void)
 {
     return false;

libraries/AP_HAL_Linux/GPIO_Sysfs.h

@@ -49,13 +49,6 @@ public:
      */
     AP_HAL::DigitalSource *channel(uint16_t vpin) override;
 
-    /*
-     * Currently this function always returns false.
-     */
-    bool attach_interrupt(uint8_t interrupt_num,
-                          irq_handler_fn_t p,
-                          INTERRUPT_TRIGGER_TYPE mode) override;
-
     /*
      * Currently this function always returns false.
      */