iio: humidity: hts221: support active-low interrupts

Add support for active low interrupts (IRQF_TRIGGER_LOW and
IRQF_TRIGGER_FALLING). Configure the device as active high or low
according to the requested irq line.

Signed-off-by: Lorenzo Bianconi <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/humidity/hts221.h

···
 extern const struct dev_pm_ops hts221_pm_ops;
 
 int hts221_config_drdy(struct hts221_hw *hw, bool enable);
+int hts221_write_with_mask(struct hts221_hw *hw, u8 addr, u8 mask, u8 val);
 int hts221_probe(struct iio_dev *iio_dev);
 int hts221_set_enable(struct hts221_hw *hw, bool enable);
 int hts221_allocate_buffers(struct hts221_hw *hw);

drivers/iio/humidity/hts221_buffer.c

···
 
 #include "hts221.h"
 
+#define HTS221_REG_DRDY_HL_ADDR		0x22
+#define HTS221_REG_DRDY_HL_MASK		BIT(7)
 #define HTS221_REG_STATUS_ADDR		0x27
 #define HTS221_RH_DRDY_MASK		BIT(1)
 #define HTS221_TEMP_DRDY_MASK		BIT(0)
···
 int hts221_allocate_trigger(struct hts221_hw *hw)
 {
 	struct iio_dev *iio_dev = iio_priv_to_dev(hw);
+	bool irq_active_low = false;
 	unsigned long irq_type;
 	int err;
 
···
 	case IRQF_TRIGGER_HIGH:
 	case IRQF_TRIGGER_RISING:
 		break;
+	case IRQF_TRIGGER_LOW:
+	case IRQF_TRIGGER_FALLING:
+		irq_active_low = true;
+		break;
 	default:
 		dev_info(hw->dev,
 			 "mode %lx unsupported, using IRQF_TRIGGER_RISING\n",
···
 		break;
 	}
 
+	err = hts221_write_with_mask(hw, HTS221_REG_DRDY_HL_ADDR,
+				     HTS221_REG_DRDY_HL_MASK, irq_active_low);
+	if (err < 0)
+		return err;
 	err = devm_request_threaded_irq(hw->dev, hw->irq, NULL,
 					hts221_trigger_handler_thread,
 					irq_type | IRQF_ONESHOT,

drivers/iio/humidity/hts221_core.c

···
 	IIO_CHAN_SOFT_TIMESTAMP(2),
 };
 
-static int hts221_write_with_mask(struct hts221_hw *hw, u8 addr, u8 mask,
-				  u8 val)
+int hts221_write_with_mask(struct hts221_hw *hw, u8 addr, u8 mask, u8 val)
 {
 	u8 data;
 	int err;