This makes the warning of implicit declaration of free_irq go.
CC [M] sound/oss/sb_ess.o
sound/oss/sb_ess.c: In function `ess_dsp_init':
sound/oss/sb_ess.c:1341: warning: implicit declaration of function `free_irq'
--- 2.5/sound/oss/sb_ess.c 2002-07-31 19:09:34.000000000 +0200
+++ 2.5c/sound/oss/sb_ess.c 2002-11-27 12:37:39.000000000 +0100
@@ -187,6 +187,7 @@
#include <linux/delay.h>
#include <linux/spinlock.h>
+#include <linux/interrupt.h>
#include "sound_config.h"
#include "sb_mixer.h"