[PATCH] linux-2.5.57_timer-none_A0.patch

This creates an empty timer_opt structure (timer_none) which is then
used as a default initializer to the timer pointer.  This lets us avoid
having to check before dereferencing the timer in future code.

arch/i386/kernel/time.c

@@ -78,7 +78,8 @@ spinlock_t rtc_lock = SPIN_LOCK_UNLOCKED;
 spinlock_t i8253_lock = SPIN_LOCK_UNLOCKED;
 EXPORT_SYMBOL(i8253_lock);
 
-struct timer_opts* timer;
+extern struct timer_opts timer_none;
+struct timer_opts* timer = &timer_none;
 
 /*
  * This version of gettimeofday has microsecond resolution

arch/i386/kernel/timers/Makefile

@@ -2,6 +2,6 @@
 # Makefile for x86 timers
 #
 
-obj-y := timer.o timer_tsc.o timer_pit.o
+obj-y := timer.o timer_none.o timer_tsc.o timer_pit.o
 
 obj-$(CONFIG_X86_CYCLONE)	+= timer_cyclone.o

arch/i386/kernel/timers/timer_none.c

+#include <asm/timer.h>
+
+static int init_none(void)
+{
+	return 0;
+}
+
+static void mark_offset_none(void)
+{
+	/* nothing needed */
+}
+
+static unsigned long get_offset_none(void)
+{
+	return 0;
+}
+
+
+/* tsc timer_opts struct */
+struct timer_opts timer_none = {
+	.init =		init_none, 
+	.mark_offset =	mark_offset_none, 
+	.get_offset =	get_offset_none,
+};