Hi,

2.6.3 compiled fine for me.  After patching it to 2.6.4-rc2-bk4 I obtain 
the following compilation error:

--------
   CC [M]  drivers/macintosh/macserial.o
drivers/macintosh/macserial.c: In function `rs_tiocmget':
drivers/macintosh/macserial.c:1793: error: `cmd' undeclared (first use 
in this function)
drivers/macintosh/macserial.c:1793: error: (Each undeclared identifier 
is reported only once
drivers/macintosh/macserial.c:1793: error: for each function it appears in.)
drivers/macintosh/macserial.c: In function `rs_tiocmset':
drivers/macintosh/macserial.c:1823: error: `cmd' undeclared (first use 
in this function)
drivers/macintosh/macserial.c:1813: warning: unused variable `arg'
drivers/macintosh/macserial.c:1813: warning: unused variable `bits'
make[2]: *** [drivers/macintosh/macserial.o] Error 1
make[1]: *** [drivers/macintosh] Error 2
make: *** [drivers] Error 2
--------

CPU: PowerPC G4 1MHz.  Machine: Alluminium PowerBook 15".

Here is the modification of drivers/macintosh/macserial.c file by the 
patch 2.6.4-rc2 (2.6.4-rc2-bk4 does not change this file):

-------------------------
diff -Nru a/drivers/macintosh/macserial.c b/drivers/macintosh/macserial.c
--- a/drivers/macintosh/macserial.c	Wed Mar  3 22:17:33 2004
+++ b/drivers/macintosh/macserial.c	Wed Mar  3 22:17:33 2004
@@ -1777,47 +1777,65 @@
  	return put_user(status,value);
  }

-static int get_modem_info(struct mac_serial *info, unsigned int *value)
+static int rs_tiocmget(struct tty_struct *tty, struct file *file)
  {
+	struct mac_serial * info = (struct mac_serial *)tty->driver_data;
  	unsigned char control, status;
-	unsigned int result;
  	unsigned long flags;

+#ifdef CONFIG_KGDB
+	if (info->kgdb_channel)
+		return -ENODEV;
+#endif
+	if (serial_paranoia_check(info, tty->name, __FUNCTION__))
+		return -ENODEV;
+
+	if ((cmd != TIOCGSERIAL) && (cmd != TIOCSSERIAL) &&
+	    (cmd != TIOCSERCONFIG) && (cmd != TIOCSERGSTRUCT)) {
+		if (tty->flags & (1 << TTY_IO_ERROR))
+		    return -EIO;
+	}
+
  	spin_lock_irqsave(&info->lock, flags);
  	control = info->curregs[5];
  	status = read_zsreg(info->zs_channel, 0);
  	spin_unlock_irqrestore(&info->lock, flags);
-	result =  ((control & RTS) ? TIOCM_RTS: 0)
+	return    ((control & RTS) ? TIOCM_RTS: 0)
  		| ((control & DTR) ? TIOCM_DTR: 0)
  		| ((status  & DCD) ? TIOCM_CAR: 0)
  		| ((status  & CTS) ? 0: TIOCM_CTS);
-	return put_user(result,value);
  }

-static int set_modem_info(struct mac_serial *info, unsigned int cmd,
-			  unsigned int *value)
+static int rs_tiocmset(struct tty_struct *tty, struct file *file,
+		       unsigned int set, unsigned int clear)
  {
+	struct mac_serial * info = (struct mac_serial *)tty->driver_data;
  	unsigned int arg, bits;
  	unsigned long flags;

-	if (get_user(arg, value))
-		return -EFAULT;
-	bits = (arg & TIOCM_RTS? RTS: 0) + (arg & TIOCM_DTR? DTR: 0);
-	spin_lock_irqsave(&info->lock, flags);
-	switch (cmd) {
-	case TIOCMBIS:
-		info->curregs[5] |= bits;
-		break;
-	case TIOCMBIC:
-		info->curregs[5] &= ~bits;
-		break;
-	case TIOCMSET:
-		info->curregs[5] = (info->curregs[5] & ~(DTR | RTS)) | bits;
-		break;
-	default:
-		spin_unlock_irqrestore(&info->lock, flags);
-		return -EINVAL;
+#ifdef CONFIG_KGDB
+	if (info->kgdb_channel)
+		return -ENODEV;
+#endif
+	if (serial_paranoia_check(info, tty->name, __FUNCTION__))
+		return -ENODEV;
+
+	if ((cmd != TIOCGSERIAL) && (cmd != TIOCSSERIAL) &&
+	    (cmd != TIOCSERCONFIG) && (cmd != TIOCSERGSTRUCT)) {
+		if (tty->flags & (1 << TTY_IO_ERROR))
+		    return -EIO;
  	}
+
+	spin_lock_irqsave(&info->lock, flags);
+	if (set & TIOCM_RTS)
+		info->curregs[5] |= RTS;
+	if (set & TIOCM_DTR)
+		info->curregs[5] |= DTR;
+	if (clear & TIOCM_RTS)
+		info->curregs[5] &= ~RTS;
+	if (clear & TIOCM_DTR)
+		info->curregs[5] &= ~DTR;
+
  	info->pendregs[5] = info->curregs[5];
  	write_zsreg(info->zs_channel, 5, info->curregs[5]);
  	spin_unlock_irqrestore(&info->lock, flags);
@@ -1863,12 +1881,6 @@
  	}

  	switch (cmd) {
-		case TIOCMGET:
-			return get_modem_info(info, (unsigned int *) arg);
-		case TIOCMBIS:
-		case TIOCMBIC:
-		case TIOCMSET:
-			return set_modem_info(info, cmd, (unsigned int *) arg);
  		case TIOCGSERIAL:
  			return get_serial_info(info,
  					(struct serial_struct __user *) arg);
@@ -2488,6 +2500,8 @@
  	.break_ctl = rs_break,
  	.wait_until_sent = rs_wait_until_sent,
  	.read_proc = macserial_read_proc,
+	.tiocmget = rs_tiocmget,
+	.tiocmset = rs_tiocmset,
  };

  static int macserial_init(void)

------------------------

I do not know the kernel internals, but to me it seems that cmd was 
previously a parameter in the function set_modem_info and now it does 
not exist anymore.

I attach my .config too.

Regards,
Eugen