add avivotool to build

1 files changed, 875 insertions, 0 deletions

diff --git a/xf86i2c.c b/xf86i2c.c
new file mode 100644
index 0000000..ed82218
--- /dev/null
+++ b/xf86i2c.c
@@ -0,0 +1,875 @@
+/*
+ * Copyright (C) 1998 Itai Nahshon, Michael Schimek
+ *
+ * The original code was derived from and inspired by 
+ * the I2C driver from the Linux kernel.
+ *      (c) 1998 Gerd Knorr <kraxel@cs.tu-berlin.de>
+ */
+
+#include <sys/time.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include "xf86i2c.h"
+
+#define I2C_TIMEOUT(x)	/*(x)*/  /* Report timeouts */
+#define I2C_TRACE(x)    /*(x)*/  /* Report progress */
+
+/* Set which OSs have bad gettimeofday resolution. */
+#if defined(SVR4) && !defined(sun)
+#define BAD_GETTIMEOFDAY_RESOLUTION
+#endif
+
+
+/* This is the default I2CUDelay function if not supplied by the driver.
+ * High level I2C interfaces implementing the bus protocol in hardware
+ * should supply this function too.
+ *
+ * Delay execution at least usec microseconds.
+ * All values 0 to 1e6 inclusive must be expected.
+ */
+
+#ifdef BAD_GETTIMEOFDAY_RESOLUTION
+/*
+ * This is temporary until a better, portable
+ * way is found. Adjust bogo_usec to match CPU speed.
+ */
+static int bogo_usec = 500;
+
+static void
+I2CUDelay(I2CBusPtr b, int usec)
+{
+    volatile long i;
+
+    if (usec > 0)
+	for (i = usec * bogo_usec; i > 0; i--)
+	    /* (perhaps hw delay action) */;
+}
+#else
+static void
+I2CUDelay(I2CBusPtr b, int usec)
+{
+#if 0
+  struct timeval begin, cur;
+  long d_secs, d_usecs;
+  long diff;
+
+  if (usec > 0) {
+    X_GETTIMEOFDAY(&begin);
+    do {
+      /* It would be nice to use {xf86}usleep, 
+       * but usleep (1) takes >10000 usec !
+       */
+      X_GETTIMEOFDAY(&cur);
+      d_secs  = (cur.tv_sec - begin.tv_sec);
+      d_usecs = (cur.tv_usec - begin.tv_usec);
+      diff = d_secs*1000000 + d_usecs;
+    } while (diff>=0 && diff< (usec + 1));
+  }
+#else
+  usleep(usec);
+#endif
+}
+#endif
+
+/* Most drivers will register just with GetBits/PutBits functions.
+ * The following functions implement a software I2C protocol
+ * by using the promitive functions given by the driver.
+ * ================================================================
+ *
+ * It is assumed that there is just one master on the I2C bus, therefore
+ * there is no explicit test for conflits.
+ */
+
+#define RISEFALLTIME 2 /* usec, actually 300 to 1000 ns according to the i2c specs */
+
+/* Some devices will hold SCL low to slow down the bus or until 
+ * ready for transmission.
+ *
+ * This condition will be noticed when the master tries to raise
+ * the SCL line. You can set the timeout to zero if the slave device
+ * does not support this clock synchronization.
+ */
+
+static Bool
+I2CRaiseSCL(I2CBusPtr b, int sda, int timeout)
+{
+    int i, scl;
+
+    b->I2CPutBits(b, 1, sda);
+    b->I2CUDelay(b, b->RiseFallTime);
+
+    for (i = timeout; i > 0; i -= b->RiseFallTime) {
+	b->I2CGetBits(b, &scl, &sda);
+	if (scl) break;
+	b->I2CUDelay(b, b->RiseFallTime);
+    }
+
+    if (i <= 0) {
+	I2C_TIMEOUT(ErrorF("[I2CRaiseSCL(<%s>, %d, %d) timeout]", b->BusName, sda, timeout));    
+	return FALSE;
+    }
+
+    return TRUE;
+}
+
+/* Send a start signal on the I2C bus. The start signal notifies
+ * devices that a new transaction is initiated by the bus master.
+ *
+ * The start signal is always followed by a slave address.
+ * Slave addresses are 8+ bits. The first 7 bits identify the
+ * device and the last bit signals if this is a read (1) or
+ * write (0) operation.
+ *
+ * There may be more than one start signal on one transaction.
+ * This happens for example on some devices that allow reading
+ * of registers. First send a start bit followed by the device
+ * address (with the last bit 0) and the register number. Then send
+ * a new start bit with the device address (with the last bit 1)
+ * and then read the value from the device.
+ *
+ * Note this is function does not implement a multiple master
+ * arbitration procedure.
+ */
+
+static Bool
+I2CStart(I2CBusPtr b, int timeout)
+{
+    if (!I2CRaiseSCL(b, 1, timeout))
+	return FALSE;
+
+    b->I2CPutBits(b, 1, 0);
+    b->I2CUDelay(b, b->HoldTime);
+    b->I2CPutBits(b, 0, 0);
+    b->I2CUDelay(b, b->HoldTime);
+
+    I2C_TRACE(ErrorF("\ni2c: <"));
+
+    return TRUE;
+}
+
+/* This is the default I2CStop function if not supplied by the driver.
+ *
+ * Signal devices on the I2C bus that a transaction on the
+ * bus has finished. There may be more than one start signal
+ * on a transaction but only one stop signal.
+ */
+
+static void
+I2CStop(I2CDevPtr d)
+{
+    I2CBusPtr b = d->pI2CBus;
+
+    b->I2CPutBits(b, 0, 0);
+    b->I2CUDelay(b, b->RiseFallTime);
+
+    b->I2CPutBits(b, 1, 0);
+    b->I2CUDelay(b, b->HoldTime);
+    b->I2CPutBits(b, 1, 1);
+    b->I2CUDelay(b, b->HoldTime);
+
+    I2C_TRACE(ErrorF(">\n"));
+}
+
+/* Write/Read a single bit to/from a device.
+ * Return FALSE if a timeout occurs.
+ */
+
+static Bool
+I2CWriteBit(I2CBusPtr b, int sda, int timeout)
+{
+    Bool r;
+
+    b->I2CPutBits(b, 0, sda);
+    b->I2CUDelay(b, b->RiseFallTime);
+
+    r = I2CRaiseSCL(b, sda, timeout);
+    b->I2CUDelay(b, b->HoldTime);
+
+    b->I2CPutBits(b, 0, sda);
+    b->I2CUDelay(b, b->HoldTime);
+
+    return r;
+}
+
+static Bool
+I2CReadBit(I2CBusPtr b, int *psda, int timeout)
+{
+    Bool r;
+    int scl;
+
+    r = I2CRaiseSCL(b, 1, timeout);
+    b->I2CUDelay(b, b->HoldTime);
+
+    b->I2CGetBits(b, &scl, psda);
+
+    b->I2CPutBits(b, 0, 1);
+    b->I2CUDelay(b, b->HoldTime);
+
+    return r;
+}
+
+/* This is the default I2CPutByte function if not supplied by the driver.
+ *
+ * A single byte is sent to the device.
+ * The function returns FALSE if a timeout occurs, you should send 
+ * a stop condition afterwards to reset the bus.
+ *
+ * A timeout occurs,
+ * if the slave pulls SCL to slow down the bus more than ByteTimeout usecs,
+ * or slows down the bus for more than BitTimeout usecs for each bit,
+ * or does not send an ACK bit (0) to acknowledge the transmission within
+ * AcknTimeout usecs, but a NACK (1) bit.
+ *
+ * AcknTimeout must be at least b->HoldTime, the other timeouts can be
+ * zero according to the comment on I2CRaiseSCL.
+ */
+
+static Bool
+I2CPutByte(I2CDevPtr d, I2CByte data)
+{
+    Bool r;
+    int i, scl, sda;
+    I2CBusPtr b = d->pI2CBus;
+
+    if (!I2CWriteBit(b, (data >> 7) & 1, d->ByteTimeout))
+	return FALSE;
+
+    for (i = 6; i >= 0; i--)
+	if (!I2CWriteBit(b, (data >> i) & 1, d->BitTimeout))
+	    return FALSE;
+
+    b->I2CPutBits(b, 0, 1);
+    b->I2CUDelay(b, b->RiseFallTime);
+
+    r = I2CRaiseSCL(b, 1, b->HoldTime);
+
+    if (r) {
+    	for (i = d->AcknTimeout; i > 0; i -= b->HoldTime) {
+	    b->I2CUDelay(b, b->HoldTime);
+	    b->I2CGetBits(b, &scl, &sda);
+	    if (sda == 0) break;
+	}
+
+	if (i <= 0) {
+	    I2C_TIMEOUT(ErrorF("[I2CPutByte(<%s>, 0x%02x, %d, %d, %d) timeout]", 
+				       b->BusName, data, d->BitTimeout, 
+				       d->ByteTimeout, d->AcknTimeout));
+	    r = FALSE;
+	}
+
+	I2C_TRACE(ErrorF("W%02x%c ", (int) data, sda ? '-' : '+'));
+    }
+
+    b->I2CPutBits(b, 0, 1);
+    b->I2CUDelay(b, b->HoldTime);
+
+    return r;
+}
+
+/* This is the default I2CGetByte function if not supplied by the driver.
+ *
+ * A single byte is read from the device.
+ * The function returns FALSE if a timeout occurs, you should send
+ * a stop condition afterwards to reset the bus.
+ * 
+ * A timeout occurs,
+ * if the slave pulls SCL to slow down the bus more than ByteTimeout usecs,
+ * or slows down the bus for more than b->BitTimeout usecs for each bit.
+ *
+ * ByteTimeout must be at least b->HoldTime, the other timeouts can be
+ * zero according to the comment on I2CRaiseSCL.
+ *
+ * For the <last> byte in a sequence the acknowledge bit NACK (1), 
+ * otherwise ACK (0) will be sent.
+ */
+
+static Bool
+I2CGetByte(I2CDevPtr d, I2CByte *data, Bool last)
+{
+    int i, sda;
+    I2CBusPtr b = d->pI2CBus;
+
+    b->I2CPutBits(b, 0, 1);
+    b->I2CUDelay(b, b->RiseFallTime);
+
+    if (!I2CReadBit(b, &sda, d->ByteTimeout))
+	return FALSE;
+
+    *data = (sda > 0) << 7;
+
+    for (i = 6; i >= 0; i--)
+	if (!I2CReadBit(b, &sda, d->BitTimeout))
+	    return FALSE;
+	else
+	    *data |= (sda > 0) << i;
+
+    if (!I2CWriteBit(b, last ? 1 : 0, d->BitTimeout))
+	return FALSE;
+
+    I2C_TRACE(ErrorF("R%02x%c ", (int) *data, last ? '+' : '-'));
+
+    return TRUE;
+}
+
+/* This is the default I2CAddress function if not supplied by the driver.
+ *
+ * It creates the start condition, followed by the d->SlaveAddr.
+ * Higher level functions must call this routine rather than
+ * I2CStart/PutByte because a hardware I2C master may not be able 
+ * to send a slave address without a start condition.
+ *
+ * The same timeouts apply as with I2CPutByte and additional a
+ * StartTimeout, similar to the ByteTimeout but for the start 
+ * condition.
+ *
+ * In case of a timeout, the bus is left in a clean idle condition.
+ * I. e. you *must not* send a Stop. If this function succeeds, you *must*.
+ *
+ * The slave address format is 16 bit, with the legacy _8_bit_ slave address
+ * in the least significant byte. This is, the slave address must include the
+ * R/_W flag as least significant bit.
+ *
+ * The most significant byte of the address will be sent _after_ the LSB, 
+ * but only if the LSB indicates:
+ * a) an 11 bit address, this is LSB = 1111 0xxx.
+ * b) a 'general call address', this is LSB = 0000 000x - see the I2C specs
+ *    for more.
+ */
+
+static Bool
+I2CAddress(I2CDevPtr d, I2CSlaveAddr addr)
+{
+    if (I2CStart(d->pI2CBus, d->StartTimeout)) {
+	if (I2CPutByte(d, addr & 0xFF)) {
+	    if ((addr & 0xF8) != 0xF0 &&
+		(addr & 0xFE) != 0x00)
+		return TRUE;
+
+	    if (I2CPutByte(d, (addr >> 8) & 0xFF))
+		return TRUE;
+	}
+
+	I2CStop(d);
+    }
+
+    return FALSE;
+}
+
+/* These are the hardware independent I2C helper functions.
+ * ========================================================
+ */
+
+/* Function for probing. Just send the slave address 
+ * and return true if the device responds. The slave address
+ * must have the lsb set to reflect a read (1) or write (0) access.
+ * Don't expect a read- or write-only device will respond otherwise.
+ */
+
+Bool
+xf86I2CProbeAddress(I2CBusPtr b, I2CSlaveAddr addr)
+{
+    int r;
+    I2CDevRec d;
+
+    d.DevName = "Probing";
+    d.BitTimeout = b->BitTimeout;
+    d.ByteTimeout = b->ByteTimeout;
+    d.AcknTimeout = b->AcknTimeout;
+    d.StartTimeout = b->StartTimeout;
+    d.SlaveAddr = addr;
+    d.pI2CBus = b;
+    d.NextDev = NULL;
+
+    r = b->I2CAddress(&d, addr);
+
+    if (r) b->I2CStop(&d);
+
+    return r;
+}
+
+/* All functions below are related to devices and take the
+ * slave address and timeout values from an I2CDevRec. They
+ * return FALSE in case of an error (presumably a timeout).
+ */
+
+/* General purpose read and write function.
+ *
+ * 1st, if nWrite > 0
+ *   Send a start condition
+ *   Send the slave address (1 or 2 bytes) with write flag
+ *   Write n bytes from WriteBuffer
+ * 2nd, if nRead > 0
+ *   Send a start condition [again]
+ *   Send the slave address (1 or 2 bytes) with read flag
+ *   Read n bytes to ReadBuffer
+ * 3rd, if a Start condition has been successfully sent,
+ *   Send a Stop condition.
+ *
+ * The functions exits immediately when an error occures,
+ * not proceeding any data left. However, step 3 will
+ * be executed anyway to leave the bus in clean idle state. 
+ */
+
+static Bool
+I2CWriteRead(I2CDevPtr d,
+		 I2CByte *WriteBuffer, int nWrite,
+		 I2CByte *ReadBuffer,  int nRead) 
+{
+    Bool r = TRUE;
+    I2CBusPtr b = d->pI2CBus;
+    int s = 0;
+
+    if (r && nWrite > 0) {
+	r = b->I2CAddress(d, d->SlaveAddr & ~1);
+	if (r) {
+	    for (; nWrite > 0; WriteBuffer++, nWrite--)
+		if (!(r = b->I2CPutByte(d, *WriteBuffer))) 
+		    break;
+	    s++;
+	}
+    }
+
+    if (r && nRead > 0) {
+	r = b->I2CAddress(d, d->SlaveAddr | 1);
+	if (r) {
+	    for (; nRead > 0; ReadBuffer++, nRead--)
+		if (!(r = b->I2CGetByte(d, ReadBuffer, nRead == 1))) 
+		    break;
+	    s++;
+	}
+    }
+
+    if (s) b->I2CStop(d);
+
+    return r;
+}
+
+/* wrapper - for compatibility and convinience */
+
+Bool
+xf86I2CWriteRead(I2CDevPtr d,
+		 I2CByte *WriteBuffer, int nWrite,
+		 I2CByte *ReadBuffer,  int nRead) 
+{
+    I2CBusPtr b = d->pI2CBus;
+    return b->I2CWriteRead(d,WriteBuffer,nWrite,ReadBuffer,nRead);
+}
+
+/* Read a byte, the only readable register of a device.
+ */
+
+Bool
+xf86I2CReadStatus(I2CDevPtr d, I2CByte *pbyte)
+{
+    return xf86I2CWriteRead(d, NULL, 0, pbyte, 1);
+}
+
+/* Read a byte from one of the registers determined by its sub-address.
+ */
+
+Bool
+xf86I2CReadByte(I2CDevPtr d, I2CByte subaddr, I2CByte *pbyte)
+{
+    return xf86I2CWriteRead(d, &subaddr, 1, pbyte, 1);
+}
+
+/* Read bytes from subsequent registers determined by the 
+ * sub-address of the first register.
+ */
+
+Bool
+xf86I2CReadBytes(I2CDevPtr d, I2CByte subaddr, I2CByte *pbyte, int n)
+{
+    return xf86I2CWriteRead(d, &subaddr, 1, pbyte, n);
+}
+
+/* Read a word (high byte, then low byte) from one of the registers 
+ * determined by its sub-address.
+ */
+
+Bool
+xf86I2CReadWord(I2CDevPtr d, I2CByte subaddr, unsigned short *pword)
+{
+    I2CByte rb[2];
+
+    if (!xf86I2CWriteRead(d, &subaddr, 1, rb, 2)) return FALSE;
+
+    *pword = (rb[0] << 8) | rb[1];
+
+    return TRUE;
+}
+
+/* Write a byte to one of the registers determined by its sub-address.
+ */
+
+Bool
+xf86I2CWriteByte(I2CDevPtr d, I2CByte subaddr, I2CByte byte)
+{
+    I2CByte wb[2];
+
+    wb[0] = subaddr;
+    wb[1] = byte;
+
+    return xf86I2CWriteRead(d, wb, 2, NULL, 0);
+}
+
+/* Write bytes to subsequent registers determined by the 
+ * sub-address of the first register.
+ */
+
+Bool
+xf86I2CWriteBytes(I2CDevPtr d, I2CByte subaddr, 
+		  I2CByte *WriteBuffer, int nWrite)
+{
+    I2CBusPtr b = d->pI2CBus;
+    Bool r = TRUE;
+
+    if (nWrite > 0) {
+	r = b->I2CAddress(d, d->SlaveAddr & ~1);
+	if (r){
+	    if ((r = b->I2CPutByte(d, subaddr)))
+		for (; nWrite > 0; WriteBuffer++, nWrite--)
+		    if (!(r = b->I2CPutByte(d, *WriteBuffer))) 
+			break;
+
+	    b->I2CStop(d);
+	}
+    }
+
+    return r;
+}
+
+/* Write a word (high byte, then low byte) to one of the registers 
+ * determined by its sub-address.
+ */
+
+Bool
+xf86I2CWriteWord(I2CDevPtr d, I2CByte subaddr, unsigned short word)
+{
+    I2CByte wb[3];
+
+    wb[0] = subaddr;
+    wb[1] = word >> 8;
+    wb[2] = word & 0xFF;
+
+    return xf86I2CWriteRead(d, wb, 3, NULL, 0);
+}
+
+/* Write a vector of bytes to not adjacent registers. This vector is, 
+ * 1st byte sub-address, 2nd byte value, 3rd byte sub-address asf.
+ * This function is intended to initialize devices. Note this function
+ * exits immediately when an error occurs, some registers may
+ * remain uninitialized.
+ */
+
+Bool
+xf86I2CWriteVec(I2CDevPtr d, I2CByte *vec, int nValues)
+{
+    I2CBusPtr b = d->pI2CBus;
+    Bool r = TRUE;
+    int s = 0;
+
+    if (nValues > 0) {
+	for (; nValues > 0; nValues--, vec += 2) {
+	    if (!(r = b->I2CAddress(d, d->SlaveAddr & ~1)))
+	    	break;
+
+	    s++;
+
+	    if (!(r = b->I2CPutByte(d, vec[0])))
+		break;
+
+	    if (!(r = b->I2CPutByte(d, vec[1]))) 
+		break;
+	}
+
+	if (s > 0) b->I2CStop(d);	
+    }
+
+    return r;
+}
+
+/* Administrative functions.
+ * =========================
+ */
+
+/* Allocates an I2CDevRec for you and initializes with propper defaults
+ * you may modify before calling xf86I2CDevInit. Your I2CDevRec must
+ * contain at least a SlaveAddr, and a pI2CBus pointer to the bus this
+ * device shall be linked to.
+ *
+ * See function I2CAddress for the slave address format. Always set
+ * the least significant bit, indicating a read or write access, to zero.
+ */
+
+I2CDevPtr
+xf86CreateI2CDevRec(void) 
+{
+    return calloc(1, sizeof(I2CDevRec));
+}
+
+/* Unlink an I2C device. If you got the I2CDevRec from xf86CreateI2CDevRec
+ * you should set <unalloc> to free it.
+ */
+
+void
+xf86DestroyI2CDevRec(I2CDevPtr d, Bool unalloc) 
+{
+    if (d) {
+	I2CDevPtr *p;
+
+	/* Remove this from the list of active I2C devices. */
+
+	for (p = &d->pI2CBus->FirstDev; *p != NULL; p = &(*p)->NextDev) 
+	    if (*p == d) {
+		*p = (*p)->NextDev;
+		break;
+	    }
+
+	fprintf(stderr,
+            "I2C device \"%s:%s\" removed.\n",
+            d->pI2CBus->BusName, d->DevName);
+
+	if (unalloc) free(d);
+    }
+}
+
+/* I2C transmissions are related to an I2CDevRec you must link to a
+ * previously registered bus (see xf86I2CBusInit) before attempting
+ * to read and write data. You may call xf86I2CProbeAddress first to
+ * see if the device in question is present on this bus. 
+ *
+ * xf86I2CDevInit will not allocate an I2CBusRec for you, instead you
+ * may enter a pointer to a statically allocated I2CDevRec or the (modified)
+ * result of xf86CreateI2CDevRec.
+ *
+ * If you don't specify timeouts for the device (n <= 0), it will inherit
+ * the bus-wide defaults. The function returns TRUE on success.
+ */
+
+Bool
+xf86I2CDevInit(I2CDevPtr d) 
+{
+    I2CBusPtr b;
+
+    if (d == NULL ||
+	(b = d->pI2CBus) == NULL ||
+        (d->SlaveAddr & 1) ||
+        xf86I2CFindDev(b, d->SlaveAddr) != NULL)
+	return FALSE;
+
+    if (d->BitTimeout <= 0) d->BitTimeout = b->BitTimeout;
+    if (d->ByteTimeout <= 0) d->ByteTimeout = b->ByteTimeout;
+    if (d->AcknTimeout <= 0) d->AcknTimeout = b->AcknTimeout;
+    if (d->StartTimeout <= 0) d->StartTimeout = b->StartTimeout;
+
+    d->NextDev = b->FirstDev;
+    b->FirstDev = d;
+
+    fprintf(stderr,
+            "I2C device \"%s:%s\" registered at address 0x%02X.\n",
+            b->BusName, d->DevName, d->SlaveAddr);
+
+    return TRUE;
+}
+
+I2CDevPtr
+xf86I2CFindDev(I2CBusPtr b, I2CSlaveAddr addr) 
+{
+    I2CDevPtr d;
+
+    if (b) { 
+         for (d = b->FirstDev; d != NULL; d = d->NextDev) 
+	    if (d->SlaveAddr == addr)
+		return d;
+    }
+
+    return NULL;
+}
+
+static I2CBusPtr I2CBusList;
+
+/* Allocates an I2CBusRec for you and initializes with propper defaults
+ * you may modify before calling xf86I2CBusInit. Your I2CBusRec must
+ * contain at least a BusName, a scrnIndex (or -1), and a complete set
+ * of either high or low level I2C function pointers. You may pass
+ * bus-wide timeouts, otherwise inplausible values will be replaced
+ * with safe defaults.
+ */
+
+I2CBusPtr
+xf86CreateI2CBusRec(void) 
+{
+    I2CBusPtr b;
+
+    b = (I2CBusPtr) calloc(1, sizeof(I2CBusRec));
+
+    if (b != NULL) {
+	b->scrnIndex = -1;
+	b->HoldTime = 5; /* 100 kHz bus */
+	b->BitTimeout = 5;
+	b->ByteTimeout = 5;
+	b->AcknTimeout = 5;
+	b->StartTimeout = 5;
+	b->RiseFallTime = RISEFALLTIME;
+    }
+
+    return b;
+}
+
+/* Unregister an I2C bus. If you got the I2CBusRec from xf86CreateI2CBusRec
+ * you should set <unalloc> to free it. If you set <devs_too>, the function
+ * xf86DestroyI2CDevRec will be called for all devices linked to the bus
+ * first, passing down the <unalloc> option.
+ */
+
+void
+xf86DestroyI2CBusRec(I2CBusPtr b, Bool unalloc, Bool devs_too) 
+{
+    if (b) {
+	I2CBusPtr *p;
+
+	/* Remove this from the list of active I2C buses */
+
+	for (p = &I2CBusList; *p != NULL; p = &(*p)->NextBus) 
+	    if (*p == b) {
+		*p = (*p)->NextBus;
+		break;
+	    }
+
+	if (b->FirstDev != NULL) {
+	    if (devs_too) {
+		I2CDevPtr d;
+
+		while ((d = b->FirstDev) != NULL) {
+		    b->FirstDev = d->NextDev;
+		    xf86DestroyI2CDevRec(d, unalloc);
+		}
+	    } else {
+		if (unalloc) {
+		    fprintf(stderr, "i2c bug: Attempt to remove I2C bus \"%s\", "
+                    "but device list is not empty.\n",
+                    b->BusName);
+		    return;
+		}
+	    }
+	}
+
+	fprintf(stderr, "I2C bus \"%s\" removed.\n",
+		   b->BusName);
+
+	if (unalloc) free(b);
+    }
+}
+
+/* I2C masters have to register themselves using this function.
+ * It will not allocate an I2CBusRec for you, instead you may enter
+ * a pointer to a statically allocated I2CBusRec or the (modified)
+ * result of xf86CreateI2CBusRec. Returns TRUE on success.
+ *
+ * At this point there won't be any traffic on the I2C bus.
+ */
+
+Bool
+xf86I2CBusInit(I2CBusPtr b) 
+{
+    /* I2C buses must be identified by a unique scrnIndex 
+     * and name. If scrnIndex is unspecified (a negative value), 
+     * then the name must be unique throughout the server. 
+     */
+
+    if (b->BusName == NULL ||
+	xf86I2CFindBus(b->scrnIndex, b->BusName) != NULL)
+	return FALSE;
+
+    /* If the high level functions are not
+     * supplied, use the generic functions.
+     * In this case we need the low-level
+     * function.
+     */
+    if (b->I2CWriteRead == NULL) 
+    {
+        b->I2CWriteRead=I2CWriteRead;
+
+        if (b->I2CPutBits == NULL ||
+	    b->I2CGetBits == NULL) 
+        {
+	    if (b->I2CPutByte == NULL ||
+	        b->I2CGetByte == NULL ||
+	        b->I2CAddress == NULL ||
+	        b->I2CStart   == NULL ||
+	        b->I2CStop    == NULL)
+	        return FALSE;
+        } else { 
+	    b->I2CPutByte = I2CPutByte;
+	    b->I2CGetByte = I2CGetByte;
+	    b->I2CAddress = I2CAddress;
+	    b->I2CStop    = I2CStop;
+	    b->I2CStart   = I2CStart;
+        }
+     }
+
+    if (b->I2CUDelay == NULL)
+	b->I2CUDelay = I2CUDelay;
+
+    if (b->HoldTime < 2) b->HoldTime = 5;
+    if (b->BitTimeout <= 0) b->BitTimeout = b->HoldTime;
+    if (b->ByteTimeout <= 0) b->ByteTimeout = b->HoldTime;
+    if (b->AcknTimeout <= 0) b->AcknTimeout = b->HoldTime;
+    if (b->StartTimeout <= 0) b->StartTimeout = b->HoldTime;
+
+    /* Put new bus on list. */
+
+    b->NextBus = I2CBusList;
+    I2CBusList = b;
+
+    fprintf(stderr, "I2C bus \"%s\" initialized.\n",
+	       b->BusName);
+
+    return TRUE;
+}
+
+I2CBusPtr
+xf86I2CFindBus(int scrnIndex, char *name) 
+{
+    I2CBusPtr p;
+
+    if (name != NULL)
+	for (p = I2CBusList; p != NULL; p = p->NextBus)
+	    if (scrnIndex < 0 || p->scrnIndex == scrnIndex)
+		if (!strcmp(p->BusName, name))
+		    return p;
+    
+    return NULL;
+}
+
+/*
+ * Return an array of I2CBusPtr's related to a screen.  The caller is
+ * responsible for freeing the array.
+ */
+int
+xf86I2CGetScreenBuses(int scrnIndex, I2CBusPtr **pppI2CBus)
+{
+    I2CBusPtr pI2CBus;
+    int n = 0;
+
+    if (pppI2CBus)
+	*pppI2CBus = NULL;
+
+    for (pI2CBus = I2CBusList;  pI2CBus;  pI2CBus = pI2CBus->NextBus) {
+	if ((pI2CBus->scrnIndex >= 0) && (pI2CBus->scrnIndex != scrnIndex))
+	    continue;
+
+	n++;
+
+	if (!pppI2CBus)
+	    continue;
+
+        *pppI2CBus = realloc(*pppI2CBus, n * sizeof(I2CBusPtr));
+	*pppI2CBus[n - 1] = pI2CBus;
+    }
+
+    return n;
+}