iio: dac: mcp4922: add support to mcp4921

Add support to mcp4921 which has only one output channel.
Signed-off-by: Kory Maincent <kory.maincent@bootlin.com>
Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/r/20220624095619.1415614-1-kory.maincent@bootlin.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/dac/mcp4922.c

@@ -17,10 +17,12 @@
 #include <linux/bitops.h>
 
 #define MCP4922_NUM_CHANNELS	2
+#define MCP4921_NUM_CHANNELS	1
 
 enum mcp4922_supported_device_ids {
 	ID_MCP4902,
 	ID_MCP4912,
+	ID_MCP4921,
 	ID_MCP4922,
 };
 
@@ -105,9 +107,10 @@ static int mcp4922_write_raw(struct iio_dev *indio_dev,
 	}
 }
 
-static const struct iio_chan_spec mcp4922_channels[3][MCP4922_NUM_CHANNELS] = {
+static const struct iio_chan_spec mcp4922_channels[4][MCP4922_NUM_CHANNELS] = {
 	[ID_MCP4902] = { MCP4922_CHAN(0, 8),	MCP4922_CHAN(1, 8) },
 	[ID_MCP4912] = { MCP4922_CHAN(0, 10),	MCP4922_CHAN(1, 10) },
+	[ID_MCP4921] = { MCP4922_CHAN(0, 12),	{} },
 	[ID_MCP4922] = { MCP4922_CHAN(0, 12),	MCP4922_CHAN(1, 12) },
 };
 
@@ -154,6 +157,9 @@ static int mcp4922_probe(struct spi_device *spi)
 	indio_dev->info = &mcp4922_info;
 	indio_dev->modes = INDIO_DIRECT_MODE;
 	indio_dev->channels = mcp4922_channels[id->driver_data];
+	if (id->driver_data == ID_MCP4921)
+		indio_dev->num_channels = MCP4921_NUM_CHANNELS;
+	else
 		indio_dev->num_channels = MCP4922_NUM_CHANNELS;
 	indio_dev->name = id->name;
 
@@ -185,6 +191,7 @@ static void mcp4922_remove(struct spi_device *spi)
 static const struct spi_device_id mcp4922_id[] = {
 	{"mcp4902", ID_MCP4902},
 	{"mcp4912", ID_MCP4912},
+	{"mcp4921", ID_MCP4921},
 	{"mcp4922", ID_MCP4922},
 	{}
 };