# HG changeset patch
# Parent bd7329d84fc47ba7d0027e88ce417b6d39fd10ce
diff -r bd7329d84fc4 -r 79717e0173a8 sys/conf/NOTES
--- a/sys/conf/NOTES
+++ b/sys/conf/NOTES
@@ -445,8 +445,17 @@ options 	DEBUG_MEMGUARD
 #
 options 	DEBUG_REDZONE
 
 #
+# EARLY_PRINTF enables support for calling a special printf (eprintf)
+# very early in the kernel (before cn_init() has been called).  This
+# should only be used for debugging purposes early in boot.  Normally,
+# it is not defined.  It is commented out here because this feature
+# isn't generally available. And the required eputc() isn't defined.
+#
+#options	EARLY_PRINTF
+
+#
 # KTRACE enables the system-call tracing facility ktrace(2).  To be more
 # SMP-friendly, KTRACE uses a worker thread to process most trace events
 # asynchronously to the thread generating the event.  This requires a
 # pre-allocated store of objects representing trace events.  The
diff -r bd7329d84fc4 -r 79717e0173a8 sys/conf/options
--- a/sys/conf/options
+++ b/sys/conf/options
@@ -61,8 +61,9 @@ KDB		opt_global.h
 KDB_TRACE	opt_kdb.h
 KDB_UNATTENDED	opt_kdb.h
 KLD_DEBUG	opt_kld.h
 SYSCTL_DEBUG	opt_sysctl.h
+EARLY_PRINTF	opt_global.h
 TEXTDUMP_PREFERRED	opt_ddb.h
 TEXTDUMP_VERBOSE	opt_ddb.h
 
 # Miscellaneous options.
diff -r bd7329d84fc4 -r 79717e0173a8 sys/kern/subr_prf.c
--- a/sys/kern/subr_prf.c
+++ b/sys/kern/subr_prf.c
@@ -1136,4 +1136,26 @@ hexdump(const void *ptr, int length, con
 		printf("\n");
 	}
 }
 
+#ifdef EARLY_PRINTF
+/*
+ * Support for calling an alternate printf early in boot (like before
+ * cn_init() can be called).  Platforms need to define eputc that want
+ * to use this.
+ */
+static void
+early_putc_func(int ch, void *arg __unused)
+{
+	eputc(ch);
+}
+
+void
+eprintf(const char *fmt, ...)
+{
+	va_list ap;
+
+	va_start(ap, fmt);
+	kvprintf(fmt, early_putc_func, NULL, 10, ap);
+	va_end(ap);
+}
+#endif
diff -r bd7329d84fc4 -r 79717e0173a8 sys/sys/systm.h
--- a/sys/sys/systm.h
+++ b/sys/sys/systm.h
@@ -191,8 +191,12 @@ void	critical_exit(void);
 void	init_param1(void);
 void	init_param2(long physpages);
 void	init_static_kenv(char *, size_t);
 void	tablefull(const char *);
+#ifdef  EARLY_PRINTF
+void	eprintf(const char *, ...) __printflike(1, 2);
+void	eputc(int ch);
+#endif
 int	kvprintf(char const *, void (*)(int, void*), void *, int,
 	    __va_list) __printflike(1, 0);
 void	log(int, const char *, ...) __printflike(2, 3);
 void	log_console(struct uio *);