machine: switch to modern interrupt registration method

This saves about 112 bytes in flash and 288 bytes in RAM when the UART
is not used.

src/machine/machine_atsamd51.go

@@ -639,7 +639,7 @@ type UART struct {
 	Buffer    *RingBuffer
 	Bus       *sam.SERCOM_USART_INT_Type
 	SERCOM    uint8
-	IRQVal uint32 // RXC interrupt
+	Interrupt interrupt.Interrupt // RXC interrupt
 }
 
 var (
@@ -651,7 +651,6 @@ var (
 		Buffer: NewRingBuffer(),
 		Bus:    sam.SERCOM3_USART_INT,
 		SERCOM: 3,
-		IRQVal: sam.IRQ_SERCOM3_2, // RXC interrupt
 	}
 
 	// The second hardware serial port on the SAMD51. Uses the SERCOM0 interface.
@@ -659,10 +658,15 @@ var (
 		Buffer: NewRingBuffer(),
 		Bus:    sam.SERCOM0_USART_INT,
 		SERCOM: 0,
-		IRQVal: sam.IRQ_SERCOM0_2, // RXC interrupt
 	}
 )
 
+func init() {
+	// Register RXC interrupts.
+	UART1.Interrupt = interrupt.New(sam.IRQ_SERCOM3_2, UART1.handleInterrupt)
+	UART2.Interrupt = interrupt.New(sam.IRQ_SERCOM0_2, UART2.handleInterrupt)
+}
+
 const (
 	sampleRate16X = 16
 	lsbFirst      = 1
@@ -766,7 +770,7 @@ func (uart UART) Configure(config UARTConfig) error {
 	// > position in the INTFLAG register of respective peripheral.
 	// Therefore, if we only need to listen to the RXC interrupt source (in bit
 	// position 2), we only need interrupt source 2 for this SERCOM device.
-	arm.EnableIRQ(uart.IRQVal)
+	uart.Interrupt.Enable()
 
 	return nil
 }
@@ -794,18 +798,10 @@ func (uart UART) WriteByte(c byte) error {
 	return nil
 }
 
-//go:export SERCOM3_2_IRQHandler
+func (uart *UART) handleInterrupt(interrupt.Interrupt) {
-func handleSERCOM3_2() {
 	// should reset IRQ
-	UART1.Receive(byte((UART1.Bus.DATA.Get() & 0xFF)))
+	uart.Receive(byte((uart.Bus.DATA.Get() & 0xFF)))
-	UART1.Bus.INTFLAG.SetBits(sam.SERCOM_USART_INT_INTFLAG_RXC)
+	uart.Bus.INTFLAG.SetBits(sam.SERCOM_USART_INT_INTFLAG_RXC)
-}
-
-//go:export SERCOM0_2_IRQHandler
-func handleSERCOM0_2() {
-	// should reset IRQ
-	UART2.Receive(byte((UART2.Bus.DATA.Get() & 0xFF)))
-	UART2.Bus.INTFLAG.SetBits(sam.SERCOM_USART_INT_INTFLAG_RXC)
 }
 
 // I2C on the SAMD51.