[avr] Added SPI.notUsingInterrupt() (Andrew Kroll)

libraries/SPI/SPI.cpp

@@ -151,3 +151,45 @@ void SPIClass::usingInterrupt(uint8_t interruptNumber)
   interrupts();
 }
 
+void SPIClass::notUsingInterrupt(uint8_t interruptNumber)
+{
+  // Once in mode 2 we can't go back to 0 without a proper reference count
+  if (interruptMode == 2)
+    return;
+  uint8_t mask = 0;
+  uint8_t sreg = SREG;
+  noInterrupts(); // Protect from a scheduler and prevent transactionBegin
+  switch (interruptNumber) {
+  #ifdef SPI_INT0_MASK
+  case 0: mask = SPI_INT0_MASK; break;
+  #endif
+  #ifdef SPI_INT1_MASK
+  case 1: mask = SPI_INT1_MASK; break;
+  #endif
+  #ifdef SPI_INT2_MASK
+  case 2: mask = SPI_INT2_MASK; break;
+  #endif
+  #ifdef SPI_INT3_MASK
+  case 3: mask = SPI_INT3_MASK; break;
+  #endif
+  #ifdef SPI_INT4_MASK
+  case 4: mask = SPI_INT4_MASK; break;
+  #endif
+  #ifdef SPI_INT5_MASK
+  case 5: mask = SPI_INT5_MASK; break;
+  #endif
+  #ifdef SPI_INT6_MASK
+  case 6: mask = SPI_INT6_MASK; break;
+  #endif
+  #ifdef SPI_INT7_MASK
+  case 7: mask = SPI_INT7_MASK; break;
+  #endif
+  default:
+    break;
+    // this case can't be reached
+  }
+  interruptMask &= ~mask;
+  if (!interruptMask)
+    interruptMode = 0;
+  SREG = sreg;
+}

libraries/SPI/SPI.h

@@ -20,6 +20,9 @@
 // usingInterrupt(), and SPISetting(clock, bitOrder, dataMode)
 #define SPI_HAS_TRANSACTION 1
 
+// SPI_HAS_NOTUSINGINTERRUPT means that SPI has notUsingInterrupt() method
+#define SPI_HAS_NOTUSINGINTERRUPT 1
+
 // Uncomment this line to add detection of mismatched begin/end transactions.
 // A mismatch occurs if other libraries fail to use SPI.endTransaction() for
 // each SPI.beginTransaction().  Connect an LED to this pin.  The LED will turn
@@ -154,6 +157,13 @@ public:
   // with attachInterrupt.  If SPI is used from a different interrupt
   // (eg, a timer), interruptNumber should be 255.
   static void usingInterrupt(uint8_t interruptNumber);
+  // And this does the opposite.
+  static void notUsingInterrupt(uint8_t interruptNumber);
+  // Note: the usingInterrupt and notUsingInterrupt functions should
+  // not to be called from ISR context or inside a transaction.
+  // For details see:
+  // https://github.com/arduino/Arduino/pull/2381
+  // https://github.com/arduino/Arduino/pull/2449
 
   // Before using SPI.transfer() or asserting chip select pins,
   // this function is used to gain exclusive access to the SPI bus