iio: adc: ad7476: Add support for TI ADS786X ADCs

Add support for Texas Instruments ADS7866, ADS7867 and ADS7868
8/10/12 bit Single channel ADC.

Datasheet: http://www.ti.com/lit/ds/symlink/ads7868.pdfSigned-off-by: Ricardo Ribalda Delgado <ricardo@ribalda.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/Kconfig

@@ -57,14 +57,17 @@ config AD7298
 	  module will be called ad7298.
 
 config AD7476
-	tristate "Analog Devices AD7476 and similar 1-channel ADCs driver"
+	tristate "Analog Devices AD7476 1-channel ADCs driver and other similar devices from AD an TI"
 	depends on SPI
 	select IIO_BUFFER
 	select IIO_TRIGGERED_BUFFER
 	help
-	  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).
+	  Say yes here to build support for the following SPI analog to
+	  digital converters (ADCs):
+	  Analog Devices: AD7273, AD7274, AD7276, AD7277, AD7278, AD7475,
+	  AD7476, AD7477, AD7478, AD7466, AD7467, AD7468, AD7495, AD7910,
+	  AD7920.
+	  Texas Instruments: ADS7866, ADS7867, ADS7868.
 
 	  To compile this driver as a module, choose M here: the
 	  module will be called ad7476.

drivers/iio/adc/ad7476.c

@@ -59,6 +59,9 @@ enum ad7476_supported_device_ids {
 	ID_ADC081S,
 	ID_ADC101S,
 	ID_ADC121S,
+	ID_ADS7866,
+	ID_ADS7867,
+	ID_ADS7868,
 };
 
 static irqreturn_t ad7476_trigger_handler(int irq, void  *p)
@@ -157,6 +160,8 @@ static int ad7476_read_raw(struct iio_dev *indio_dev,
 #define AD7940_CHAN(bits) _AD7476_CHAN((bits), 15 - (bits), \
 		BIT(IIO_CHAN_INFO_RAW))
 #define AD7091R_CHAN(bits) _AD7476_CHAN((bits), 16 - (bits), 0)
+#define ADS786X_CHAN(bits) _AD7476_CHAN((bits), 12 - (bits), \
+		BIT(IIO_CHAN_INFO_RAW))
 
 static const struct ad7476_chip_info ad7476_chip_info_tbl[] = {
 	[ID_AD7091R] = {
@@ -209,6 +214,18 @@ static const struct ad7476_chip_info ad7476_chip_info_tbl[] = {
 		.channel[0] = ADC081S_CHAN(12),
 		.channel[1] = IIO_CHAN_SOFT_TIMESTAMP(1),
 	},
+	[ID_ADS7866] = {
+		.channel[0] = ADS786X_CHAN(12),
+		.channel[1] = IIO_CHAN_SOFT_TIMESTAMP(1),
+	},
+	[ID_ADS7867] = {
+		.channel[0] = ADS786X_CHAN(10),
+		.channel[1] = IIO_CHAN_SOFT_TIMESTAMP(1),
+	},
+	[ID_ADS7868] = {
+		.channel[0] = ADS786X_CHAN(8),
+		.channel[1] = IIO_CHAN_SOFT_TIMESTAMP(1),
+	},
 };
 
 static const struct iio_info ad7476_info = {
@@ -314,6 +331,9 @@ static const struct spi_device_id ad7476_id[] = {
 	{"adc081s", ID_ADC081S},
 	{"adc101s", ID_ADC101S},
 	{"adc121s", ID_ADC121S},
+	{"ads7866", ID_ADS7866},
+	{"ads7867", ID_ADS7867},
+	{"ads7868", ID_ADS7868},
 	{}
 };
 MODULE_DEVICE_TABLE(spi, ad7476_id);