dahdi: Add capability to generate events on buffer underruns and overruns

Add BUFFEVENTS and individual buffer event channel flags so that DAHDI can
notify userspace processes when it is dropping data.  This can be useful when
trouble shooting fax problems since DAHDI currently silently discards data
becasuse of scheduling latency.  With this change, Asterisk could log an event
as opposed to just leaving it up to the tone detectors to figure out there was
some unexpected phase shift.

Acked-by: Shaun Ruffell <sruffell@digium.com>
(original patch by Matt Fredrickson)


git-svn-id: http://svn.asterisk.org/svn/dahdi/linux/trunk@9905 a0bf4364-ded3-4de4-8d8a-66a801d63aff

3 files changed, 48 insertions, 0 deletions

diff --git a/drivers/dahdi/dahdi-base.c b/drivers/dahdi/dahdi-base.c
index d9b8408..5c57b2c 100644
--- a/drivers/dahdi/dahdi-base.c
+++ b/drivers/dahdi/dahdi-base.c
@@ -6278,6 +6278,13 @@ static int dahdi_chan_ioctl(struct file *file, unsigned int cmd, unsigned long d
 		}
 		break;
 #endif
+	case DAHDI_BUFFER_EVENTS:
+		if (get_user(j, (int __user *)data) != -EFAULT && j)
+			set_bit(DAHDI_FLAGBIT_BUFEVENTS, &chan->flags);
+		else
+			clear_bit(DAHDI_FLAGBIT_BUFEVENTS, &chan->flags);
+
+		break;
 	default:
 		return dahdi_chanandpseudo_ioctl(file, cmd, data);
 	}
@@ -7060,6 +7067,7 @@ static inline void __dahdi_getbuf_chunk(struct dahdi_chan *ss, unsigned char *tx
 	int getlin;
 	/* How many bytes we need to process */
 	int bytes = DAHDI_CHUNKSIZE, left;
+	bool needtxunderrun = false;
 	int x;
 
 	/* Let's pick something to transmit.  First source to
@@ -7201,13 +7209,25 @@ out in the later versions, and is put back now. */
 			} else {
 				memset(txb, 0xFF, bytes);
 			}
+			needtxunderrun += bytes;
 			bytes = 0;
 		} else {
 			memset(txb, DAHDI_LIN2X(0, ms), bytes);	/* Lastly we use silence on telephony channels */
+			needtxunderrun += bytes;
 			bytes = 0;
 		}
 	}
 
+	if (needtxunderrun) {
+		if (!test_bit(DAHDI_FLAGBIT_TXUNDERRUN, &ms->flags)) {
+			if (test_bit(DAHDI_FLAGBIT_BUFEVENTS, &ms->flags))
+				__qevent(ms, DAHDI_EVENT_WRITE_UNDERRUN);
+			set_bit(DAHDI_FLAGBIT_TXUNDERRUN, &ms->flags);
+		}
+	} else {
+		clear_bit(DAHDI_FLAGBIT_TXUNDERRUN, &ms->flags);
+	}
+
 #ifdef CONFIG_DAHDI_MIRROR
 	if (ss->txmirror) {
 		spin_lock(&ss->txmirror->lock);
@@ -8383,6 +8403,15 @@ that the waitqueue is empty. */
 #endif
 	}
 
+	if (bytes) {
+		if (!test_bit(DAHDI_FLAGBIT_RXOVERRUN, &ms->flags)) {
+			if (test_bit(DAHDI_FLAGBIT_BUFEVENTS, &ms->flags))
+				__qevent(ms, DAHDI_EVENT_READ_OVERRUN);
+			set_bit(DAHDI_FLAGBIT_RXOVERRUN, &ms->flags);
+		}
+	} else {
+		clear_bit(DAHDI_FLAGBIT_RXOVERRUN, &ms->flags);
+	}
 }
 
 static inline void __dahdi_putbuf_chunk(struct dahdi_chan *ss, unsigned char *rxb)
diff --git a/include/dahdi/kernel.h b/include/dahdi/kernel.h
index 6b5f4a4..d3beabe 100644
--- a/include/dahdi/kernel.h
+++ b/include/dahdi/kernel.h
@@ -719,6 +719,9 @@ enum {
 	DAHDI_FLAGBIT_LOOPED	= 18,	/*!< Loopback the receive data from the channel to the transmit */
 	DAHDI_FLAGBIT_MTP2	= 19,	/*!< Repeats last message in buffer and also discards repeating messages sent to us */
 	DAHDI_FLAGBIT_HDLC56	= 20,	/*!< Sets the given channel (if in HDLC mode) to use 56K HDLC instead of 64K  */
+	DAHDI_FLAGBIT_BUFEVENTS	= 21,	/*!< Report buffer events */
+	DAHDI_FLAGBIT_TXUNDERRUN = 22,	/*!< Transmit underrun condition */
+	DAHDI_FLAGBIT_RXOVERRUN = 23,	/*!< Receive overrun condition */
 	DAHDI_FLAGBIT_DEVFILE	= 25,	/*!< Channel has a sysfs dev file */
 };
 
@@ -783,6 +786,9 @@ struct dahdi_count {
 #define DAHDI_FLAG_LOOPED	DAHDI_FLAG(LOOPED)
 #define DAHDI_FLAG_MTP2		DAHDI_FLAG(MTP2)
 #define DAHDI_FLAG_HDLC56	DAHDI_FLAG(HDLC56)
+#define DAHDI_FLAG_BUFEVENTS	DAHDI_FLAG(BUFEVENTS)
+#define DAHDI_FLAG_TXUNDERRUN	DAHDI_FLAG(TXUNDERRUN)
+#define DAHDI_FLAG_RXOVERRUN	DAHDI_FLAG(RXOVERRUN)
 
 struct dahdi_span_ops {
 	struct module *owner;		/*!< Which module is exporting this span. */
diff --git a/include/dahdi/user.h b/include/dahdi/user.h
index 1159fbf..6b666b9 100644
--- a/include/dahdi/user.h
+++ b/include/dahdi/user.h
@@ -448,6 +448,12 @@ enum dahdi_maint_mode {
 /* The echo canceler's NLP (only) was enabled */
 #define DAHDI_EVENT_EC_NLP_ENABLED	28
 
+/* The channel's read buffer encountered an overrun condition */
+#define DAHDI_EVENT_READ_OVERRUN	29
+
+/* The channel's write buffer encountered an underrun condition */
+#define DAHDI_EVENT_WRITE_UNDERRUN	30
+
 #define DAHDI_EVENT_PULSEDIGIT		(1 << 16)	/* This is OR'd with the digit received */
 #define DAHDI_EVENT_DTMFDOWN		(1 << 17)	/* Ditto for DTMF key down event */
 #define DAHDI_EVENT_DTMFUP		(1 << 18)	/* Ditto for DTMF key up event */
@@ -1085,6 +1091,13 @@ struct dahdi_vmwi_info {
 #define DAHDI_TXMIRROR			_IOW(DAHDI_CODE, 104, int)
 #endif /* CONFIG_DAHDI_MIRROR */
 
+/*
+  Set the desired state for channel buffer event generation which is disabled
+  by default to allow for backwards compatibility for dumb users of channels
+  such as pattern utilities.
+ */
+#define DAHDI_BUFFER_EVENTS		_IOW(DAHDI_CODE, 105, int)
+
 /* Get current status IOCTL */
 /* Defines for Radio Status (dahdi_radio_stat.radstat) bits */