[PATCH] ti-adc081c: Add support for adc101c* and adc121c*

[Crestez Dan Leonard]

These chips has an almost identical interface but a deal with a
different number of value bits. Datasheet links for comparison:

 * http://www.ti.com/lit/ds/symlink/adc081c021.pdf
 * http://www.ti.com/lit/ds/symlink/adc101c021.pdf
 * http://www.ti.com/lit/ds/symlink/adc121c021.pdf

I am working with an ADC121C021 chip but it makes a lot of sense to support the
entire family with a single driver.

Signed-off-by: Crestez Dan Leonard <leonard.crestez@xxxxxxxxx>
---
 drivers/iio/adc/Kconfig      |  6 +++---
 drivers/iio/adc/ti-adc081c.c | 33 ++++++++++++++++++++++++++++-----
 2 files changed, 31 insertions(+), 8 deletions(-)

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 9ddcd5d..a2d0db5 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -378,11 +378,11 @@ config ROCKCHIP_SARADC
 	  module will be called rockchip_saradc.
 
 config TI_ADC081C
-	tristate "Texas Instruments ADC081C021/027"
+	tristate "Texas Instruments ADC081C/ADC101C/ADC121C family"
 	depends on I2C
 	help
-	  If you say yes here you get support for Texas Instruments ADC081C021
-	  and ADC081C027 ADC chips.
+	  If you say yes here you get support for Texas Instruments ADC081C,
+	  ADC101C and ADC121C ADC chips.
 
 	  This driver can also be built as a module. If so, the module will be
 	  called ti-adc081c.
diff --git a/drivers/iio/adc/ti-adc081c.c b/drivers/iio/adc/ti-adc081c.c
index ecbc121..66ade3f 100644
--- a/drivers/iio/adc/ti-adc081c.c
+++ b/drivers/iio/adc/ti-adc081c.c
@@ -1,9 +1,21 @@
 /*
+ * TI ADC081C/ADC101C/ADC121C 8/10/12-bit ADC driver
+ *
  * Copyright (C) 2012 Avionic Design GmbH
+ * Copyright (C) 2016 Intel
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
+ *
+ * Datasheets:
+ * 	http://www.ti.com/lit/ds/symlink/adc081c021.pdf
+ * 	http://www.ti.com/lit/ds/symlink/adc101c021.pdf
+ *	http://www.ti.com/lit/ds/symlink/adc121c021.pdf
+ *
+ * The devices have a very similar interface and differ mostly in the number of
+ * bits handled. For the 8-bit and 10-bit models the least-significant 4 or 2
+ * bits of value registers are reserved.
  */
 
 #include <linux/err.h>
@@ -17,6 +29,9 @@
 struct adc081c {
 	struct i2c_client *i2c;
 	struct regulator *ref;
+
+	/* 8, 10 or 12 */
+	int bits;
 };
 
 #define REG_CONV_RES 0x00
@@ -34,7 +49,7 @@ static int adc081c_read_raw(struct iio_dev *iio,
 		if (err < 0)
 			return err;
 
-		*value = (err >> 4) & 0xff;
+		*value = (err & 0xFFF) >> (12 - adc->bits);
 		return IIO_VAL_INT;
 
 	case IIO_CHAN_INFO_SCALE:
@@ -43,7 +58,7 @@ static int adc081c_read_raw(struct iio_dev *iio,
 			return err;
 
 		*value = err / 1000;
-		*shift = 8;
+		*shift = adc->bits;
 
 		return IIO_VAL_FRACTIONAL_LOG2;
 
@@ -72,6 +87,9 @@ static int adc081c_probe(struct i2c_client *client,
 	struct adc081c *adc;
 	int err;
 
+	if (id->driver_data != 8 && id->driver_data != 10 && id->driver_data != 12)
+		return -EINVAL;
+
 	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WORD_DATA))
 		return -EOPNOTSUPP;
 
@@ -81,6 +99,7 @@ static int adc081c_probe(struct i2c_client *client,
 
 	adc = iio_priv(iio);
 	adc->i2c = client;
+	adc->bits = id->driver_data;
 
 	adc->ref = devm_regulator_get(&client->dev, "vref");
 	if (IS_ERR(adc->ref))
@@ -124,14 +143,18 @@ static int adc081c_remove(struct i2c_client *client)
 }
 
 static const struct i2c_device_id adc081c_id[] = {
-	{ "adc081c", 0 },
+	{ "adc081c",  8 },
+	{ "adc101c", 10 },
+	{ "adc121c", 12 },
 	{ }
 };
 MODULE_DEVICE_TABLE(i2c, adc081c_id);
 
 #ifdef CONFIG_OF
 static const struct of_device_id adc081c_of_match[] = {
-	{ .compatible = "ti,adc081c" },
+	{ .compatible = "ti,adc081c", .data = (void*) 8 },
+	{ .compatible = "ti,adc101c", .data = (void*)10 },
+	{ .compatible = "ti,adc121c", .data = (void*)12 },
 	{ }
 };
 MODULE_DEVICE_TABLE(of, adc081c_of_match);
@@ -149,5 +172,5 @@ static struct i2c_driver adc081c_driver = {
 module_i2c_driver(adc081c_driver);
 
 MODULE_AUTHOR("Thierry Reding <thierry.reding@xxxxxxxxxxxxxxxxx>");
-MODULE_DESCRIPTION("Texas Instruments ADC081C021/027 driver");
+MODULE_DESCRIPTION("Texas Instruments ADC081C/ADC101C/ADC121C driver");
 MODULE_LICENSE("GPL v2");
-- 
2.8.0.rc3