iio: amplifiers: ad8366: add support for HMC1119 Attenuator

This change adds support for the HMC1119 Silicon Digial Attenuator. The
HMC1119 is a broadband, highly accurate, 7-bit digital attenuator,
operating from 0.1 GHz to 6.0 GHz with 31.5 dB attenuation control range
in 0.25 dB steps.

Link: https://www.analog.com/media/en/technical-documentation/data-sheets/hmc1119.pdf

Signed-off-by: Sergiu Cuciurean <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/amplifiers/ad8366.c

···
  *   AD8366 Dual-Digital Variable Gain Amplifier (VGA)
  *   ADA4961 BiCMOS RF Digital Gain Amplifier (DGA)
  *   ADL5240 Digitally controlled variable gain amplifier (VGA)
+ *   HMC1119 0.25 dB LSB, 7-Bit, Silicon Digital Attenuator
  *
  * Copyright 2012-2019 Analog Devices Inc.
  */
···
 	ID_AD8366,
 	ID_ADA4961,
 	ID_ADL5240,
+	ID_HMC1119,
 };
 
 struct ad8366_info {
···
 		.gain_min = -11500,
 		.gain_max = 20000,
 	},
+	[ID_HMC1119] = {
+		.gain_min = -31750,
+		.gain_max = 0,
+	},
 };
 
 static int ad8366_write(struct iio_dev *indio_dev,
···
 		break;
 	case ID_ADL5240:
 		st->data[0] = (ch_a & 0x3F);
+		break;
+	case ID_HMC1119:
+		st->data[0] = ch_a;
 		break;
 	}
 
···
 			break;
 		case ID_ADL5240:
 			gain = 20000 - 31500 + code * 500;
+			break;
+		case ID_HMC1119:
+			gain = -1 * code * 250;
 			break;
 		}
 
···
 		break;
 	case ID_ADL5240:
 		code = ((gain - 500 - 20000) / 500) & 0x3F;
+		break;
+	case ID_HMC1119:
+		code = (abs(gain) / 250) & 0x7F;
 		break;
 	}
 
···
 		break;
 	case ID_ADA4961:
 	case ID_ADL5240:
+	case ID_HMC1119:
 		st->reset_gpio = devm_gpiod_get(&spi->dev, "reset",
 			GPIOD_OUT_HIGH);
 		indio_dev->channels = ada4961_channels;
···
 	{"ad8366",  ID_AD8366},
 	{"ada4961", ID_ADA4961},
 	{"adl5240", ID_ADL5240},
+	{"hmc1119", ID_HMC1119},
 	{}
 };
 MODULE_DEVICE_TABLE(spi, ad8366_id);