[PATCH hwmon-next 1/2] hwmon: (mlxreg-fan) Modify PWM connectivity validation

[Vadim Pasternak <vadimp@nvidia.com>]

Validate PWM connectivity only for additional PWM - "pwm1" is connected
on all systems, while "pwm2" - "pwm4" are optional. Validate
connectivity only for optional attributes by reading of related "pwm{n}"
registers - in case "pwm{n}" is not connected, register value is
supposed to be 0xff.

Signed-off-by: Vadim Pasternak <vadimp@nvidia.com>
---
 drivers/hwmon/mlxreg-fan.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/hwmon/mlxreg-fan.c b/drivers/hwmon/mlxreg-fan.c
index feab9ec6a6ca..8e5cd6991929 100644
--- a/drivers/hwmon/mlxreg-fan.c
+++ b/drivers/hwmon/mlxreg-fan.c
@@ -488,9 +488,14 @@ static int mlxreg_fan_config(struct mlxreg_fan *fan,
 				return -EINVAL;
 			}
 
-			err = mlxreg_pwm_connect_verify(fan, data);
-			if (err)
-				return err;
+			/* Validate if more then one PWM is connected. */
+			if (pwm_num) {
+				err = mlxreg_pwm_connect_verify(fan, data);
+				if (err < 0)
+					return err;
+				else if (!err)
+					continue;
+			}
 
 			fan->pwm[pwm_num].reg = data->reg;
 			fan->pwm[pwm_num].connected = true;
-- 
2.20.1