[PATCH 1/2] thermal: generic-adc: make lookup table optional

[Jean-Francois Dagenais <jeff.dagenais@gmail.com>]

Certain ADC channels, such as the xilinx-ams temperature channels, give
milliCelcius already when read with iio_read_channel_processed.

Rather than having to provide a 1:1 dummy lookup table, simply allow to
bypass the mechanism.

Signed-off-by: Jean-Francois Dagenais <jeff.dagenais@gmail.com>
---
 drivers/thermal/thermal-generic-adc.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/thermal/thermal-generic-adc.c b/drivers/thermal/thermal-generic-adc.c
index e22fc60ad36d..deb244f12de4 100644
--- a/drivers/thermal/thermal-generic-adc.c
+++ b/drivers/thermal/thermal-generic-adc.c
@@ -29,6 +29,9 @@ static int gadc_thermal_adc_to_temp(struct gadc_thermal_info *gti, int val)
 	int temp, temp_hi, temp_lo, adc_hi, adc_lo;
 	int i;
 
+	if (!gti->lookup_table)
+		return val;
+
 	for (i = 0; i < gti->nlookup_table; i++) {
 		if (val >= gti->lookup_table[2 * i + 1])
 			break;
@@ -81,9 +84,9 @@ static int gadc_thermal_read_linear_lookup_table(struct device *dev,
 
 	ntable = of_property_count_elems_of_size(np, "temperature-lookup-table",
 						 sizeof(u32));
-	if (ntable < 0) {
-		dev_err(dev, "Lookup table is not provided\n");
-		return ntable;
+	if (ntable <= 0) {
+		dev_notice(dev, "no lookup table, assuming DAC channel returns milliCelcius\n");
+		return 0;
 	}
 
 	if (ntable % 2) {
-- 
2.11.0