[PATCH] hwmon: bt1-pvt: Declare Temp- and Volt-to-N poly when alarms are enabled

[Serge Semin <Sergey.Semin@baikalelectronics.ru>]

Clang-based kernel building with W=1 warns that some static const
variables are unused:

drivers/hwmon/bt1-pvt.c:67:30: warning: unused variable 'poly_temp_to_N' [-Wunused-const-variable]
static const struct pvt_poly poly_temp_to_N = {
                             ^
drivers/hwmon/bt1-pvt.c:99:30: warning: unused variable 'poly_volt_to_N' [-Wunused-const-variable]
static const struct pvt_poly poly_volt_to_N = {
                             ^

Indeed these polynomials are utilized only when the PVT sensor alarms are
enabled. In that case they are used to convert the temperature and
voltage alarm limits from normal quantities (Volts and degree Celsius) to
the sensor data representation N = [0, 1023]. Otherwise when alarms are
disabled the driver only does the detected data conversion to the human
readable form and doesn't need that polynomials defined. So let's declare
the Temp-to-N and Volt-to-N polynomials only if the PVT alarms are
switched on at compile-time.

Note gcc with W=1 doesn't notice the problem.

Fixes: 87976ce2825d ("hwmon: Add Baikal-T1 PVT sensor driver")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Cc: Maxim Kaurkin <Maxim.Kaurkin@baikalelectronics.ru>
Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
---
 drivers/hwmon/bt1-pvt.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/hwmon/bt1-pvt.c b/drivers/hwmon/bt1-pvt.c
index 1a9772fb1f73..1a5212c04549 100644
--- a/drivers/hwmon/bt1-pvt.c
+++ b/drivers/hwmon/bt1-pvt.c
@@ -64,6 +64,7 @@ static const struct pvt_sensor_info pvt_info[] = {
  *     48380,
  * where T = [-48380, 147438] mC and N = [0, 1023].
  */
+#if defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
 static const struct pvt_poly poly_temp_to_N = {
 	.total_divider = 10000,
 	.terms = {
@@ -74,6 +75,7 @@ static const struct pvt_poly poly_temp_to_N = {
 		{0, 1720400, 1, 1}
 	}
 };
+#endif /* CONFIG_SENSORS_BT1_PVT_ALARMS */
 
 static const struct pvt_poly poly_N_to_temp = {
 	.total_divider = 1,
@@ -96,6 +98,7 @@ static const struct pvt_poly poly_N_to_temp = {
  * N = (18658e-3*V - 11572) / 10,
  * V = N * 10^5 / 18658 + 11572 * 10^4 / 18658.
  */
+#if defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
 static const struct pvt_poly poly_volt_to_N = {
 	.total_divider = 10,
 	.terms = {
@@ -103,6 +106,7 @@ static const struct pvt_poly poly_volt_to_N = {
 		{0, -11572, 1, 1}
 	}
 };
+#endif /* CONFIG_SENSORS_BT1_PVT_ALARMS */
 
 static const struct pvt_poly poly_N_to_volt = {
 	.total_divider = 10,
-- 
2.26.2