media: lirc: report ir receiver overflow

If the driver reports that the hardware had an overflow, report this to
userspace. It would be nice to know when this happens, and not just get
a long space.

This change has been tested with lircd, ir-ctl, and ir-keytable.
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

Documentation/userspace-api/media/lirc.h.rst.exceptions

@@ -11,12 +11,14 @@ ignore define LIRC_SPACE
 ignore define LIRC_PULSE
 ignore define LIRC_FREQUENCY
 ignore define LIRC_TIMEOUT
+ignore define LIRC_OVERFLOW
 ignore define LIRC_VALUE
 ignore define LIRC_MODE2
 ignore define LIRC_IS_SPACE
 ignore define LIRC_IS_PULSE
 ignore define LIRC_IS_FREQUENCY
 ignore define LIRC_IS_TIMEOUT
+ignore define LIRC_IS_OVERFLOW
 
 ignore define LIRC_MODE2SEND
 ignore define LIRC_SEND2MODE
@@ -75,6 +77,7 @@ ignore define PULSE_MASK
 ignore define LIRC_MODE2_SPACE
 ignore define LIRC_MODE2_PULSE
 ignore define LIRC_MODE2_TIMEOUT
+ignore define LIRC_MODE2_OVERFLOW
 
 ignore define LIRC_VALUE_MASK
 ignore define LIRC_MODE2_MASK

Documentation/userspace-api/media/rc/lirc-dev-intro.rst

@@ -103,11 +103,11 @@ on the following table.
 
     ``LIRC_MODE2_PULSE``
 
-        Signifies the presence of IR in microseconds.
+        Signifies the presence of IR in microseconds, also known as *flash*.
 
     ``LIRC_MODE2_SPACE``
 
-        Signifies absence of IR in microseconds.
+        Signifies absence of IR in microseconds, also known as *gap*.
 
     ``LIRC_MODE2_FREQUENCY``
 
@@ -121,6 +121,13 @@ on the following table.
         to no IR being detected, this packet will be sent, with the number
         of microseconds with no IR.
 
+    ``LIRC_MODE2_OVERFLOW``
+
+        Signifies that the IR receiver encounter an overflow, and some IR
+        is missing. The IR data after this should be correct again. The
+        actual value is not important, but this is set to 0xffffff by the
+        kernel for compatibility with lircd.
+
 .. _lirc-mode-pulse:
 
 ``LIRC_MODE_PULSE``

drivers/media/rc/lirc_dev.c

@@ -44,14 +44,13 @@ void lirc_raw_event(struct rc_dev *dev, struct ir_raw_event ev)
 	/* Receiver overflow, data missing */
 	if (ev.overflow) {
 		/*
-		 * Userspace expects a long space event before the start of
-		 * the signal to use as a sync.  This may be done with repeat
-		 * packets and normal samples.  But if an overflow has been sent
-		 * then we assume that a long time has passed, so we send a
-		 * space with the maximum time value.
+		 * Send lirc overflow message. This message is unknown to
+		 * lircd, but it will interpret this as a long space as
+		 * long as the value is set to high value. This resets its
+		 * decoder state.
 		 */
-		sample = LIRC_SPACE(LIRC_VALUE_MASK);
-		dev_dbg(&dev->dev, "delivering overflow space to lirc_dev\n");
+		sample = LIRC_OVERFLOW(LIRC_VALUE_MASK);
+		dev_dbg(&dev->dev, "delivering overflow to lirc_dev\n");
 
 	/* Carrier reports */
 	} else if (ev.carrier_report) {

drivers/media/rc/rc-loopback.c

@@ -112,7 +112,11 @@ static int loop_tx_ir(struct rc_dev *dev, unsigned *txbuf, unsigned count)
 		rawir.pulse = i % 2 ? false : true;
 		rawir.duration = txbuf[i];
 
-		ir_raw_event_store_with_filter(dev, &rawir);
+		/* simulate overflow if ridiculously long pulse was sent */
+		if (rawir.pulse && rawir.duration > MS_TO_US(50))
+			ir_raw_event_overflow(dev);
+		else
+			ir_raw_event_store_with_filter(dev, &rawir);
 	}
 
 	if (lodev->carrierreport) {

include/uapi/linux/lirc.h

@@ -16,14 +16,16 @@
 #define LIRC_MODE2_PULSE     0x01000000
 #define LIRC_MODE2_FREQUENCY 0x02000000
 #define LIRC_MODE2_TIMEOUT   0x03000000
+#define LIRC_MODE2_OVERFLOW  0x04000000
 
 #define LIRC_VALUE_MASK      0x00FFFFFF
 #define LIRC_MODE2_MASK      0xFF000000
 
-#define LIRC_SPACE(val) (((val)&LIRC_VALUE_MASK) | LIRC_MODE2_SPACE)
-#define LIRC_PULSE(val) (((val)&LIRC_VALUE_MASK) | LIRC_MODE2_PULSE)
-#define LIRC_FREQUENCY(val) (((val)&LIRC_VALUE_MASK) | LIRC_MODE2_FREQUENCY)
-#define LIRC_TIMEOUT(val) (((val)&LIRC_VALUE_MASK) | LIRC_MODE2_TIMEOUT)
+#define LIRC_SPACE(val) (((val) & LIRC_VALUE_MASK) | LIRC_MODE2_SPACE)
+#define LIRC_PULSE(val) (((val) & LIRC_VALUE_MASK) | LIRC_MODE2_PULSE)
+#define LIRC_FREQUENCY(val) (((val) & LIRC_VALUE_MASK) | LIRC_MODE2_FREQUENCY)
+#define LIRC_TIMEOUT(val) (((val) & LIRC_VALUE_MASK) | LIRC_MODE2_TIMEOUT)
+#define LIRC_OVERFLOW(val) (((val) & LIRC_VALUE_MASK) | LIRC_MODE2_OVERFLOW)
 
 #define LIRC_VALUE(val) ((val)&LIRC_VALUE_MASK)
 #define LIRC_MODE2(val) ((val)&LIRC_MODE2_MASK)
@@ -32,6 +34,7 @@
 #define LIRC_IS_PULSE(val) (LIRC_MODE2(val) == LIRC_MODE2_PULSE)
 #define LIRC_IS_FREQUENCY(val) (LIRC_MODE2(val) == LIRC_MODE2_FREQUENCY)
 #define LIRC_IS_TIMEOUT(val) (LIRC_MODE2(val) == LIRC_MODE2_TIMEOUT)
+#define LIRC_IS_OVERFLOW(val) (LIRC_MODE2(val) == LIRC_MODE2_OVERFLOW)
 
 /* used heavily by lirc userspace */
 #define lirc_t int