diff --git a/drivers/staging/comedi/drivers/addi-data/hwdrv_apci3xxx.c b/drivers/staging/comedi/drivers/addi-data/hwdrv_apci3xxx.c
index 8c825a796713..edb91849881a 100644
--- a/drivers/staging/comedi/drivers/addi-data/hwdrv_apci3xxx.c
+++ b/drivers/staging/comedi/drivers/addi-data/hwdrv_apci3xxx.c
@@ -49,19 +49,23 @@ static int apci3xxx_ai_configure(struct comedi_device *dev,
 	if (aref_mode != 0 && aref_mode != 1)
 		return -EINVAL;
 
-	if (!(board->b_AvailableConvertUnit & (1 << time_base)))
+	if (time_base > 2)
 		return -EINVAL;
 
 	if (reload_time > 0xffff)
 		return -EINVAL;
 
+	time_base = 1 << time_base;
+	if (!(board->ai_conv_units & time_base))
+		return -EINVAL;
+
 	switch (time_base) {
-	case 0:
-		acq_ns = reload_time;		/* ns */
-	case 1:
-		acq_ns = reload_time * 1000;	/* us */
-	case 2:
-		acq_ns = reload_time * 1000000;	/* ms */
+	case CONV_UNIT_NS:
+		acq_ns = reload_time;
+	case CONV_UNIT_US:
+		acq_ns = reload_time * 1000;
+	case CONV_UNIT_MS:
+		acq_ns = reload_time * 1000000;
 	default:
 		return -EINVAL;
 	}
diff --git a/drivers/staging/comedi/drivers/addi_apci_3xxx.c b/drivers/staging/comedi/drivers/addi_apci_3xxx.c
index c6cd30bdce96..8deec2b0734f 100644
--- a/drivers/staging/comedi/drivers/addi_apci_3xxx.c
+++ b/drivers/staging/comedi/drivers/addi_apci_3xxx.c
@@ -27,6 +27,10 @@
 
 #include "../comedidev.h"
 
+#define CONV_UNIT_NS		(1 << 0)
+#define CONV_UNIT_US		(1 << 1)
+#define CONV_UNIT_MS		(1 << 2)
+
 static const struct comedi_lrange apci3xxx_ai_range = {
 	8, {
 		BIP_RANGE(10),
@@ -81,7 +85,7 @@ struct apci3xxx_boardinfo {
 	int i_NbrAiChannel;
 	int i_NbrAiChannelDiff;
 	unsigned int ai_maxdata;
-	unsigned char b_AvailableConvertUnit;
+	unsigned char ai_conv_units;
 	unsigned int ui_MinAcquisitiontimeNs;
 	unsigned int has_ao:1;
 	unsigned int has_dig_in:1;
@@ -96,7 +100,7 @@ static const struct apci3xxx_boardinfo apci3xxx_boardtypes[] = {
 		.i_NbrAiChannel		= 16,
 		.i_NbrAiChannelDiff	= 8,
 		.ai_maxdata		= 0x0fff,
-		.b_AvailableConvertUnit	= 6,
+		.ai_conv_units		= CONV_UNIT_MS | CONV_UNIT_US,
 		.ui_MinAcquisitiontimeNs = 10000,
 		.has_ttl_io		= 1,
 	},
@@ -106,7 +110,7 @@ static const struct apci3xxx_boardinfo apci3xxx_boardtypes[] = {
 		.i_NbrAiChannel		= 8,
 		.i_NbrAiChannelDiff	= 4,
 		.ai_maxdata		= 0x0fff,
-		.b_AvailableConvertUnit	= 6,
+		.ai_conv_units		= CONV_UNIT_MS | CONV_UNIT_US,
 		.ui_MinAcquisitiontimeNs = 10000,
 		.has_ttl_io		= 1,
 	},
@@ -116,7 +120,7 @@ static const struct apci3xxx_boardinfo apci3xxx_boardtypes[] = {
 		.i_NbrAiChannel		= 4,
 		.i_NbrAiChannelDiff	= 2,
 		.ai_maxdata		= 0x0fff,
-		.b_AvailableConvertUnit	= 6,
+		.ai_conv_units		= CONV_UNIT_MS | CONV_UNIT_US,
 		.ui_MinAcquisitiontimeNs = 10000,
 		.has_ttl_io		= 1,
 	},
@@ -126,7 +130,7 @@ static const struct apci3xxx_boardinfo apci3xxx_boardtypes[] = {
 		.i_NbrAiChannel		= 16,
 		.i_NbrAiChannelDiff	= 8,
 		.ai_maxdata		= 0xffff,
-		.b_AvailableConvertUnit	= 6,
+		.ai_conv_units		= CONV_UNIT_MS | CONV_UNIT_US,
 		.ui_MinAcquisitiontimeNs = 10000,
 		.has_ttl_io		= 1,
 	},
@@ -136,7 +140,7 @@ static const struct apci3xxx_boardinfo apci3xxx_boardtypes[] = {
 		.i_NbrAiChannel		= 8,
 		.i_NbrAiChannelDiff	= 4,
 		.ai_maxdata		= 0xffff,
-		.b_AvailableConvertUnit	= 6,
+		.ai_conv_units		= CONV_UNIT_MS | CONV_UNIT_US,
 		.ui_MinAcquisitiontimeNs = 10000,
 		.has_ttl_io		= 1,
 	},
@@ -146,7 +150,7 @@ static const struct apci3xxx_boardinfo apci3xxx_boardtypes[] = {
 		.i_NbrAiChannel		= 4,
 		.i_NbrAiChannelDiff	= 2,
 		.ai_maxdata		= 0xffff,
-		.b_AvailableConvertUnit	= 6,
+		.ai_conv_units		= CONV_UNIT_MS | CONV_UNIT_US,
 		.ui_MinAcquisitiontimeNs = 10000,
 		.has_ttl_io		= 1,
 	},
@@ -156,7 +160,7 @@ static const struct apci3xxx_boardinfo apci3xxx_boardtypes[] = {
 		.i_NbrAiChannel		= 16,
 		.i_NbrAiChannelDiff	= 8,
 		.ai_maxdata		= 0x0fff,
-		.b_AvailableConvertUnit	= 6,
+		.ai_conv_units		= CONV_UNIT_MS | CONV_UNIT_US,
 		.ui_MinAcquisitiontimeNs = 5000,
 		.has_dig_in		= 1,
 		.has_dig_out		= 1,
@@ -168,7 +172,7 @@ static const struct apci3xxx_boardinfo apci3xxx_boardtypes[] = {
 		.i_NbrAiChannel		= 8,
 		.i_NbrAiChannelDiff	= 4,
 		.ai_maxdata		= 0x0fff,
-		.b_AvailableConvertUnit	= 6,
+		.ai_conv_units		= CONV_UNIT_MS | CONV_UNIT_US,
 		.ui_MinAcquisitiontimeNs = 5000,
 		.has_dig_in		= 1,
 		.has_dig_out		= 1,
@@ -180,7 +184,7 @@ static const struct apci3xxx_boardinfo apci3xxx_boardtypes[] = {
 		.i_NbrAiChannel		= 4,
 		.i_NbrAiChannelDiff	= 2,
 		.ai_maxdata		= 0x0fff,
-		.b_AvailableConvertUnit	= 6,
+		.ai_conv_units		= CONV_UNIT_MS | CONV_UNIT_US,
 		.ui_MinAcquisitiontimeNs = 5000,
 		.has_dig_in		= 1,
 		.has_dig_out		= 1,
@@ -192,7 +196,7 @@ static const struct apci3xxx_boardinfo apci3xxx_boardtypes[] = {
 		.i_NbrAiChannel		= 16,
 		.i_NbrAiChannelDiff	= 8,
 		.ai_maxdata		= 0xffff,
-		.b_AvailableConvertUnit	= 6,
+		.ai_conv_units		= CONV_UNIT_MS | CONV_UNIT_US,
 		.ui_MinAcquisitiontimeNs = 5000,
 		.has_dig_in		= 1,
 		.has_dig_out		= 1,
@@ -204,7 +208,7 @@ static const struct apci3xxx_boardinfo apci3xxx_boardtypes[] = {
 		.i_NbrAiChannel		= 8,
 		.i_NbrAiChannelDiff	= 4,
 		.ai_maxdata		= 0xffff,
-		.b_AvailableConvertUnit	= 6,
+		.ai_conv_units		= CONV_UNIT_MS | CONV_UNIT_US,
 		.ui_MinAcquisitiontimeNs = 5000,
 		.has_dig_in		= 1,
 		.has_dig_out		= 1,
@@ -216,7 +220,7 @@ static const struct apci3xxx_boardinfo apci3xxx_boardtypes[] = {
 		.i_NbrAiChannel		= 4,
 		.i_NbrAiChannelDiff	= 2,
 		.ai_maxdata		= 0xffff,
-		.b_AvailableConvertUnit	= 6,
+		.ai_conv_units		= CONV_UNIT_MS | CONV_UNIT_US,
 		.ui_MinAcquisitiontimeNs = 5000,
 		.has_dig_in		= 1,
 		.has_dig_out		= 1,
@@ -228,7 +232,7 @@ static const struct apci3xxx_boardinfo apci3xxx_boardtypes[] = {
 		.i_NbrAiChannel		= 16,
 		.i_NbrAiChannelDiff	= 8,
 		.ai_maxdata		= 0x0fff,
-		.b_AvailableConvertUnit	= 6,
+		.ai_conv_units		= CONV_UNIT_MS | CONV_UNIT_US,
 		.ui_MinAcquisitiontimeNs = 10000,
 		.has_ao			= 1,
 		.has_ttl_io		= 1,
@@ -239,7 +243,7 @@ static const struct apci3xxx_boardinfo apci3xxx_boardtypes[] = {
 		.i_NbrAiChannel		= 8,
 		.i_NbrAiChannelDiff	= 4,
 		.ai_maxdata		= 0x0fff,
-		.b_AvailableConvertUnit	= 6,
+		.ai_conv_units		= CONV_UNIT_MS | CONV_UNIT_US,
 		.ui_MinAcquisitiontimeNs = 10000,
 		.has_ao			= 1,
 		.has_ttl_io		= 1,
@@ -250,7 +254,7 @@ static const struct apci3xxx_boardinfo apci3xxx_boardtypes[] = {
 		.i_NbrAiChannel		= 16,
 		.i_NbrAiChannelDiff	= 8,
 		.ai_maxdata		= 0xffff,
-		.b_AvailableConvertUnit	= 6,
+		.ai_conv_units		= CONV_UNIT_MS | CONV_UNIT_US,
 		.ui_MinAcquisitiontimeNs = 10000,
 		.has_ao			= 1,
 		.has_ttl_io		= 1,
@@ -261,7 +265,7 @@ static const struct apci3xxx_boardinfo apci3xxx_boardtypes[] = {
 		.i_NbrAiChannel		= 8,
 		.i_NbrAiChannelDiff	= 4,
 		.ai_maxdata		= 0xffff,
-		.b_AvailableConvertUnit	= 6,
+		.ai_conv_units		= CONV_UNIT_MS | CONV_UNIT_US,
 		.ui_MinAcquisitiontimeNs = 10000,
 		.has_ao			= 1,
 		.has_ttl_io		= 1,
@@ -272,7 +276,7 @@ static const struct apci3xxx_boardinfo apci3xxx_boardtypes[] = {
 		.i_NbrAiChannel		= 16,
 		.i_NbrAiChannelDiff	= 8,
 		.ai_maxdata		= 0x0fff,
-		.b_AvailableConvertUnit	= 6,
+		.ai_conv_units		= CONV_UNIT_MS | CONV_UNIT_US,
 		.ui_MinAcquisitiontimeNs = 5000,
 		.has_ao			= 1,
 		.has_dig_in		= 1,
@@ -285,7 +289,7 @@ static const struct apci3xxx_boardinfo apci3xxx_boardtypes[] = {
 		.i_NbrAiChannel		= 8,
 		.i_NbrAiChannelDiff	= 4,
 		.ai_maxdata		= 0x0fff,
-		.b_AvailableConvertUnit	= 6,
+		.ai_conv_units		= CONV_UNIT_MS | CONV_UNIT_US,
 		.ui_MinAcquisitiontimeNs = 5000,
 		.has_ao			= 1,
 		.has_dig_in		= 1,
@@ -298,7 +302,7 @@ static const struct apci3xxx_boardinfo apci3xxx_boardtypes[] = {
 		.i_NbrAiChannel		= 16,
 		.i_NbrAiChannelDiff	= 8,
 		.ai_maxdata		= 0xffff,
-		.b_AvailableConvertUnit	= 6,
+		.ai_conv_units		= CONV_UNIT_MS | CONV_UNIT_US,
 		.ui_MinAcquisitiontimeNs = 5000,
 		.has_ao			= 1,
 		.has_dig_in		= 1,
@@ -311,7 +315,7 @@ static const struct apci3xxx_boardinfo apci3xxx_boardtypes[] = {
 		.i_NbrAiChannel		= 8,
 		.i_NbrAiChannelDiff	= 4,
 		.ai_maxdata		= 0xffff,
-		.b_AvailableConvertUnit	= 6,
+		.ai_conv_units		= CONV_UNIT_MS | CONV_UNIT_US,
 		.ui_MinAcquisitiontimeNs = 5000,
 		.has_ao			= 1,
 		.has_dig_in		= 1,
@@ -323,7 +327,8 @@ static const struct apci3xxx_boardinfo apci3xxx_boardtypes[] = {
 		.ai_subdev_flags	= SDF_DIFF,
 		.i_NbrAiChannelDiff	= 4,
 		.ai_maxdata		= 0xffff,
-		.b_AvailableConvertUnit	= 7,
+		.ai_conv_units		= CONV_UNIT_MS | CONV_UNIT_US |
+					  CONV_UNIT_NS,
 		.ui_MinAcquisitiontimeNs = 2500,
 		.has_dig_in		= 1,
 		.has_dig_out		= 1,
@@ -333,7 +338,7 @@ static const struct apci3xxx_boardinfo apci3xxx_boardtypes[] = {
 		.ai_subdev_flags	= SDF_DIFF,
 		.i_NbrAiChannelDiff	= 16,
 		.ai_maxdata		= 0xffff,
-		.b_AvailableConvertUnit	= 6,
+		.ai_conv_units		= CONV_UNIT_MS | CONV_UNIT_US,
 		.ui_MinAcquisitiontimeNs = 5000,
 		.has_dig_in		= 1,
 		.has_dig_out		= 1,
@@ -343,7 +348,7 @@ static const struct apci3xxx_boardinfo apci3xxx_boardtypes[] = {
 		.ai_subdev_flags	= SDF_DIFF,
 		.i_NbrAiChannelDiff	= 8,
 		.ai_maxdata		= 0xffff,
-		.b_AvailableConvertUnit	= 6,
+		.ai_conv_units		= CONV_UNIT_MS | CONV_UNIT_US,
 		.ui_MinAcquisitiontimeNs = 5000,
 		.has_dig_in		= 1,
 		.has_dig_out		= 1,
@@ -353,7 +358,7 @@ static const struct apci3xxx_boardinfo apci3xxx_boardtypes[] = {
 		.ai_subdev_flags	= SDF_DIFF,
 		.i_NbrAiChannelDiff	= 4,
 		.ai_maxdata		= 0xffff,
-		.b_AvailableConvertUnit	= 6,
+		.ai_conv_units		= CONV_UNIT_MS | CONV_UNIT_US,
 		.ui_MinAcquisitiontimeNs = 5000,
 		.has_dig_in		= 1,
 		.has_dig_out		= 1,