Index: zaptel.c
===================================================================
RCS file: /usr/cvsroot/zaptel/zaptel.c,v
retrieving revision 1.95.2.1
diff -u -r1.95.2.1 zaptel.c
--- zaptel.c	6 Oct 2004 22:11:41 -0000	1.95.2.1
+++ zaptel.c	2 Nov 2004 10:59:16 -0000
@@ -703,6 +703,20 @@
 	unsigned char *newbuf, *oldbuf;
 	unsigned long flags;
 	int x;
+
+        /* Allocate history buffer, or not.  This probably shouldn't
+	 *            be here, but it's convenient */
+       if(!j)
+       {
+          if(ss->history) kfree(ss->history);
+          ss->history = NULL;
+       }
+       else
+       {
+         if(!ss->history) ss->history=kmalloc(ZT_HISTORY_BUF_LEN, GFP_KERNEL);
+       }
+       ss->historypos=0;
+
 	/* Check numbufs */
 	if (numbufs < 2)
 		numbufs = 2;
@@ -3856,11 +3870,12 @@
 {
 	struct zt_chan *chan = chans[unit];
 	unsigned long flags;
-	int j, rv;
+	int j, k1, k2, rv;
 	int ret;
 	int oldconf;
 	void *rxgain=NULL;
 	echo_can_state_t *ec, *tec;
+	struct zt_history hist;
 
 	if (!chan)
 		return -ENOSYS;
@@ -4186,6 +4201,29 @@
 			return -EINVAL;
 		break;
 #endif
+	case ZT_GET_HISTORY:
+		if (copy_from_user(&hist,(struct zt_history *) data,sizeof(hist)))
+			return -EIO;
+
+		if (!(chan->flags & ZT_FLAG_AUDIO)) return (-EINVAL);
+		if (!chan->history) return -EINVAL;
+		j=hist.len;
+		k1=ZT_HISTORY_BUF_LEN-chan->historypos;
+		k2=chan->historypos;
+		if(j>0 && k1>0)
+		{
+			if (copy_to_user(hist.buf,chan->history+chan->historypos,min(j,k1)))
+				return -EIO;
+			j-=min(j,k1);
+		}
+		if(j>0 && k2>0)
+		{
+			if (copy_to_user(hist.buf+k1,chan->history,min(j,k2)))
+				return -EIO;
+			j-=min(j,k2);
+		}
+		/* Probably should assert j==0 here */
+		break;
 	default:
 		return zt_chanandpseudo_ioctl(inode, file, cmd, data, unit);
 	}
@@ -5371,6 +5409,15 @@
 	if (!(ms->flags &  ZT_FLAG_PSEUDO)) {
 		memcpy(ms->putlin, putlin, ZT_CHUNKSIZE * sizeof(short));
 		memcpy(ms->putraw, rxb, ZT_CHUNKSIZE);
+	}
+
+	/* Store in the history buffer */
+	if(ms->history)
+	{
+		memcpy(ms->history+ms->historypos,rxb,ZT_CHUNKSIZE);
+		ms->historypos+=ZT_CHUNKSIZE;
+		if(ms->historypos >= ZT_HISTORY_BUF_LEN)
+			ms->historypos=0;
 	}
 	
 	/* Take the rxc, twiddle it for conferencing if appropriate and put it
Index: zaptel.h
===================================================================
RCS file: /usr/cvsroot/zaptel/zaptel.h,v
retrieving revision 1.38
diff -u -r1.38 zaptel.h
--- zaptel.h	27 Sep 2004 19:50:03 -0000	1.38
+++ zaptel.h	2 Nov 2004 10:59:17 -0000
@@ -137,6 +137,8 @@
 #define ZT_MAX_NUM_BUFS		 32
 #define ZT_MAX_BUF_SPACE         32768
 
+#define ZT_HISTORY_BUF_LEN       16384 /* Count of ulaw samples */
+
 #define ZT_DEFAULT_BLOCKSIZE 1024
 #define ZT_DEFAULT_MTR_MRU	 2048
 
@@ -277,6 +279,11 @@
 int reserved[4];	/* Reserved for future expansion -- always set to 0 */
 } ZT_DIAL_PARAMS;
 
+typedef struct zt_history
+{
+	unsigned char   *buf;           /* Sample buffer */
+	int len;                /* Length of buffer, in bytes */
+} ZT_HISTORY;
 
 typedef struct zt_dynamic_span {
 	char driver[20];	/* Which low-level driver to use */
@@ -584,6 +591,11 @@
 #define ZT_TIMERPONG _IOW (ZT_CODE, 53, int)
 
 /*
+ * Return history buffer
+ */
+#define ZT_GET_HISTORY _IOR(ZT_CODE, 54, struct zt_history)
+
+/*
  * Set/get signalling freeze
  */
 #define ZT_SIGFREEZE _IOW (ZT_CODE, 54, int)
@@ -989,6 +1001,10 @@
 	wait_queue_head_t writebufq; /* write wait queue */
 	
 	int		blocksize;	/* Block size */
+
+
+        u_char          *history;       /* History buffer, for pre-ring caller ID (ZT_HISTORY_BUF_LEN) */
+        u_short         historypos;     /* Current position within buffer */
 
 	int		eventinidx;  /* out index in event buf (circular) */
 	int		eventoutidx;  /* in index in event buf (circular) */