diff --git a/drivers/aiodev/mc13xxx_adc.c b/drivers/aiodev/mc13xxx_adc.c
index 4e72048..d445d1e 100644
--- a/drivers/aiodev/mc13xxx_adc.c
+++ b/drivers/aiodev/mc13xxx_adc.c
@@ -75,8 +75,9 @@
 	return container_of(chan->aiodev, struct mc13xx_adc_data, aiodev);
 }
 
-int mc13xxx_adc_do_conversion(struct mc13xxx *mc13xxx,
-		unsigned int channel, unsigned int *sample)
+static int mc13xxx_adc_do_conversion(struct mc13xxx *mc13xxx,
+				     unsigned int channel,
+				     unsigned int *sample)
 {
 	int i;
 	int timeout = 100;