A 1.5Q kernel doesn't build correctly if COMPAT_LINUX is
enabled and the WSCONS driver is disabled on i386. The
problem is that <sys/ioctl.h> doesn't get included. 
Here's a patch to fix the problem:

Index: linux_machdep.c
===================================================================
RCS file: /cvsroot/syssrc/sys/compat/linux/arch/i386/linux_machdep.c,v
retrieving revision 1.58
diff -u -r1.58 linux_machdep.c
--- linux_machdep.c	2000/12/29 22:06:58	1.58
+++ linux_machdep.c	2001/01/26 06:25:30
@@ -64,6 +64,7 @@
 #include <sys/filedesc.h>
 #include <sys/exec_elf.h>
 #include <sys/disklabel.h>
+#include <sys/ioctl.h>
 #include <miscfs/specfs/specdev.h>
 
 #include <compat/linux/common/linux_types.h>
@@ -93,7 +94,6 @@
 #include "wsdisplay.h"
 #endif
 #if (NWSDISPLAY > 0)
-#include <sys/ioctl.h>
 #include <dev/wscons/wsconsio.h>
 #include <dev/wscons/wsdisplay_usl_io.h>
 #if defined(_KERNEL) && !defined(_LKM)


-- 
____________
Will Waites \________________________
Minister of Research and Development \____________
Idiosyntactix Strategic Arts and Science Alliance \