iio:ad7476: Add support for ad7273/ad7274/ad7276/ad7277/ad7278

The ad7276/ad7277/ad7278 are similar to the ad7476/ad7477/ad7478 but have the
same number of leading zeros as the ad7940. The ad7273/ad7274 have a extra pin
for VREF where as for the ad7276/ad7277/ad7278 VREF is taken from VDD, but
otherwise they are compatible to the ad7276/ad7277.

Signed-off-by: Lars-Peter Clausen <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/adc/Kconfig

···
 	select IIO_BUFFER
 	select IIO_TRIGGERED_BUFFER
 	help
-	  Say yes here to build support for Analog Devices AD7475, AD7476, AD7477,
-	  AD7478, AD7466, AD7467, AD7468, AD7495, AD7910, AD7920, AD7920 SPI analog
-	  to digital converters (ADC).
+	  Say yes here to build support for Analog Devices AD7273, AD7274, AD7276,
+	  AD7277, AD7278, AD7475, AD7476, AD7477, AD7478, AD7466, AD7467, AD7468,
+	  AD7495, AD7910, AD7920, AD7920 SPI analog to digital converters (ADC).
 
 	  If unsure, say N (but it's safe to say "Y").
 

drivers/iio/adc/ad7476.c

···
 };
 
 enum ad7476_supported_device_ids {
+	ID_AD7276,
+	ID_AD7277,
+	ID_AD7278,
 	ID_AD7466,
 	ID_AD7467,
 	ID_AD7468,
···
 #define AD7940_CHAN(bits) _AD7476_CHAN((bits), 15 - (bits))
 
 static const struct ad7476_chip_info ad7476_chip_info_tbl[] = {
+	[ID_AD7276] = {
+		.channel[0] = AD7940_CHAN(12),
+		.channel[1] = IIO_CHAN_SOFT_TIMESTAMP(1),
+	},
+	[ID_AD7277] = {
+		.channel[0] = AD7940_CHAN(10),
+		.channel[1] = IIO_CHAN_SOFT_TIMESTAMP(1),
+	},
+	[ID_AD7278] = {
+		.channel[0] = AD7940_CHAN(8),
+		.channel[1] = IIO_CHAN_SOFT_TIMESTAMP(1),
+	},
 	[ID_AD7466] = {
 		.channel[0] = AD7476_CHAN(12),
 		.channel[1] = IIO_CHAN_SOFT_TIMESTAMP(1),
···
 }
 
 static const struct spi_device_id ad7476_id[] = {
+	{"ad7273", ID_AD7277},
+	{"ad7274", ID_AD7276},
+	{"ad7276", ID_AD7276},
+	{"ad7277", ID_AD7277},
+	{"ad7278", ID_AD7278},
 	{"ad7466", ID_AD7466},
 	{"ad7467", ID_AD7467},
 	{"ad7468", ID_AD7468},