[PATCH v3 0/2] iio: adc: add LTC2309 support

[PATCH v3 0/2] iio: adc: add LTC2309 support

[Liam Beguin]

The LTC2309 is an 8-Channel, 12-Bit SAR ADC with an I2C Interface.

This implements support for all single-ended and differential channels,
in unipolar mode only.

Signed-off-by: Liam Beguin <liambeguin@gmail.com>
---
Changes in v3:
- fix comments, kerneldoc, and i2c_device_id
- drop DRIVER_NAME
- drop datasheet_name
- drop unused i2c clientdata
- rework .read_raw() locking, adding utility function
- remove reundant parent assignment
- use dev_err_probe
- update devm_regulator_get_optional() error handling
- Link to v2: https://lore.kernel.org/r/20230825-ltc2309-v2-0-6d75f2b3fb50@gmail.com

Changes in v2:
- reduce critical section scope to i2c accesses only
- fixup .probe() commit
- fix unbalanced regulator
- rename refcomp to vref
- update lltc,2497.yaml instead of duplicating bindings
- commit dt-bindings before driver
- fix checkpatch --strict warnings
- Link to v1: https://lore.kernel.org/r/20230824-ltc2309-v1-0-b87b4eb8030c@gmail.com

---
Liam Beguin (2):
      dt-bindings: iio: adc: add lltc,ltc2309 bindings
      iio: adc: add ltc2309 support

 .../devicetree/bindings/iio/adc/lltc,ltc2497.yaml  |  20 +-
 drivers/iio/adc/Kconfig                            |  10 +
 drivers/iio/adc/Makefile                           |   1 +
 drivers/iio/adc/ltc2309.c                          | 249 +++++++++++++++++++++
 4 files changed, 275 insertions(+), 5 deletions(-)
---
base-commit: a5e505a99ca748583dbe558b691be1b26f05d678
change-id: 20230823-ltc2309-1945e1e94931

Best regards,
-- 
Liam Beguin <liambeguin@gmail.com>

[PATCH v3 1/2] dt-bindings: iio: adc: add lltc,ltc2309 bindings

[Liam Beguin]

Add devicetree bindings for the Linear Technology LTC2309 ADC driver.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Liam Beguin <liambeguin@gmail.com>
---
 .../devicetree/bindings/iio/adc/lltc,ltc2497.yaml    | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/Documentation/devicetree/bindings/iio/adc/lltc,ltc2497.yaml b/Documentation/devicetree/bindings/iio/adc/lltc,ltc2497.yaml
index 875f394576c2..5cc6a9684077 100644
--- a/Documentation/devicetree/bindings/iio/adc/lltc,ltc2497.yaml
+++ b/Documentation/devicetree/bindings/iio/adc/lltc,ltc2497.yaml
@@ -4,21 +4,31 @@
 $id: http://devicetree.org/schemas/iio/adc/lltc,ltc2497.yaml#
 $schema: http://devicetree.org/meta-schemas/core.yaml#
 
-title: Linear Technology / Analog Devices LTC2497 ADC
+title: Linear Technology / Analog Devices LTC2497 and LTC2309 ADC
 
 maintainers:
   - Michael Hennerich <michael.hennerich@analog.com>
+  - Liam Beguin <liambeguin@gmail.com>
 
 description: |
-  16bit ADC supporting up to 16 single ended or 8 differential inputs.
-  I2C interface.
+  LTC2309:
+    low noise, low power, 8-channel, 12-bit successive approximation ADC with an
+    I2C compatible serial interface.
 
-  https://www.analog.com/media/en/technical-documentation/data-sheets/2497fb.pdf
-  https://www.analog.com/media/en/technical-documentation/data-sheets/2499fe.pdf
+    https://www.analog.com/media/en/technical-documentation/data-sheets/2309fd.pdf
+
+  LTC2497:
+  LTC2499:
+    16bit ADC supporting up to 16 single ended or 8 differential inputs.
+    I2C interface.
+
+    https://www.analog.com/media/en/technical-documentation/data-sheets/2497fb.pdf
+    https://www.analog.com/media/en/technical-documentation/data-sheets/2499fe.pdf
 
 properties:
   compatible:
     enum:
+      - lltc,ltc2309
       - lltc,ltc2497
       - lltc,ltc2499
 

-- 
2.39.0

[PATCH v3 2/2] iio: adc: add ltc2309 support

[Liam Beguin]

The LTC2309 is an 8-Channel, 12-Bit SAR ADC with an I2C Interface.

This implements support for all single-ended and differential channels,
in unipolar mode only.

Signed-off-by: Liam Beguin <liambeguin@gmail.com>
---
 drivers/iio/adc/Kconfig   |  10 ++
 drivers/iio/adc/Makefile  |   1 +
 drivers/iio/adc/ltc2309.c | 249 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 260 insertions(+)

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index dc14bde31ac1..6ec18e02faf9 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -607,6 +607,16 @@ config LPC32XX_ADC
 	  activate only one via device tree selection.  Provides direct access
 	  via sysfs.
 
+config LTC2309
+	tristate "Linear Technology LTC2309 ADC driver"
+	depends on I2C
+	help
+	  Say yes here to build support for Linear Technology LTC2309, a low
+	  noise, low power, 8-channel, 12-bit SAR ADC
+
+	  This driver can also be built as a module. If so, the module will
+	  be called ltc2309.
+
 config LTC2471
 	tristate "Linear Technology LTC2471 and LTC2473 ADC driver"
 	depends on I2C
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index eb6e891790fb..fbd86184ec94 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -56,6 +56,7 @@ obj-$(CONFIG_INTEL_MRFLD_ADC) += intel_mrfld_adc.o
 obj-$(CONFIG_LP8788_ADC) += lp8788_adc.o
 obj-$(CONFIG_LPC18XX_ADC) += lpc18xx_adc.o
 obj-$(CONFIG_LPC32XX_ADC) += lpc32xx_adc.o
+obj-$(CONFIG_LTC2309) += ltc2309.o
 obj-$(CONFIG_LTC2471) += ltc2471.o
 obj-$(CONFIG_LTC2485) += ltc2485.o
 obj-$(CONFIG_LTC2496) += ltc2496.o ltc2497-core.o
diff --git a/drivers/iio/adc/ltc2309.c b/drivers/iio/adc/ltc2309.c
new file mode 100644
index 000000000000..3f8e1d238639
--- /dev/null
+++ b/drivers/iio/adc/ltc2309.c
@@ -0,0 +1,249 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * The LTC2309 is an 8-Channel, 12-Bit SAR ADC with an I2C Interface.
+ *
+ * Datasheet:
+ * https://www.analog.com/media/en/technical-documentation/data-sheets/2309fd.pdf
+ *
+ * Copyright (c) 2023, Liam Beguin <liambeguin@gmail.com>
+ */
+#include <linux/bitfield.h>
+#include <linux/i2c.h>
+#include <linux/iio/iio.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/regulator/consumer.h>
+
+#define LTC2309_ADC_RESOLUTION	12
+
+#define LTC2309_DIN_CH_MASK	GENMASK(7, 4)
+#define LTC2309_DIN_SDN		BIT(7)
+#define LTC2309_DIN_OSN		BIT(6)
+#define LTC2309_DIN_S1		BIT(5)
+#define LTC2309_DIN_S0		BIT(4)
+#define LTC2309_DIN_UNI		BIT(3)
+#define LTC2309_DIN_SLEEP	BIT(2)
+
+/**
+ * struct ltc2309 - internal device data structure
+ * @dev:	Device reference
+ * @client:	I2C reference
+ * @vref:	External reference source
+ * @lock:	Lock to serialize data access
+ * @vref_mv	Internal voltage reference
+ */
+struct ltc2309 {
+	struct device		*dev;
+	struct i2c_client	*client;
+	struct regulator	*vref;
+	struct mutex		lock; /* serialize data access */
+	int			vref_mv;
+};
+
+/* Order matches expected channel address, See datasheet Table 1. */
+enum ltc2309_channels {
+	LTC2309_CH0_CH1 = 0,
+	LTC2309_CH2_CH3,
+	LTC2309_CH4_CH5,
+	LTC2309_CH6_CH7,
+	LTC2309_CH1_CH0,
+	LTC2309_CH3_CH2,
+	LTC2309_CH5_CH4,
+	LTC2309_CH7_CH6,
+	LTC2309_CH0,
+	LTC2309_CH2,
+	LTC2309_CH4,
+	LTC2309_CH6,
+	LTC2309_CH1,
+	LTC2309_CH3,
+	LTC2309_CH5,
+	LTC2309_CH7,
+};
+
+#define LTC2309_CHAN(_chan, _addr) {				\
+	.type = IIO_VOLTAGE,					\
+	.indexed = 1,						\
+	.address = _addr,					\
+	.channel = _chan,					\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
+	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
+}
+
+#define LTC2309_DIFF_CHAN(_chan, _chan2, _addr) {		\
+	.type = IIO_VOLTAGE,					\
+	.differential = 1,					\
+	.indexed = 1,						\
+	.address = _addr,					\
+	.channel = _chan,					\
+	.channel2 = _chan2,					\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
+	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
+}
+
+static const struct iio_chan_spec ltc2309_channels[] = {
+	LTC2309_CHAN(0, LTC2309_CH0),
+	LTC2309_CHAN(1, LTC2309_CH1),
+	LTC2309_CHAN(2, LTC2309_CH2),
+	LTC2309_CHAN(3, LTC2309_CH3),
+	LTC2309_CHAN(4, LTC2309_CH4),
+	LTC2309_CHAN(5, LTC2309_CH5),
+	LTC2309_CHAN(6, LTC2309_CH6),
+	LTC2309_CHAN(7, LTC2309_CH7),
+	LTC2309_DIFF_CHAN(0, 1, LTC2309_CH0_CH1),
+	LTC2309_DIFF_CHAN(2, 3, LTC2309_CH2_CH3),
+	LTC2309_DIFF_CHAN(4, 5, LTC2309_CH4_CH5),
+	LTC2309_DIFF_CHAN(6, 7, LTC2309_CH6_CH7),
+	LTC2309_DIFF_CHAN(1, 0, LTC2309_CH1_CH0),
+	LTC2309_DIFF_CHAN(3, 2, LTC2309_CH3_CH2),
+	LTC2309_DIFF_CHAN(5, 4, LTC2309_CH5_CH4),
+	LTC2309_DIFF_CHAN(7, 6, LTC2309_CH7_CH6),
+};
+
+static int ltc2309_read_raw_channel(struct ltc2309 *ltc2309,
+				    unsigned long address, int *val)
+{
+	int ret;
+	u16 buf;
+	u8 din;
+
+	din = FIELD_PREP(LTC2309_DIN_CH_MASK, address & 0x0f) |
+		FIELD_PREP(LTC2309_DIN_UNI, 1) |
+		FIELD_PREP(LTC2309_DIN_SLEEP, 0);
+
+	ret = i2c_smbus_write_byte(ltc2309->client, din);
+	if (ret < 0) {
+		dev_err(ltc2309->dev, "i2c command failed: %pe\n",
+			ERR_PTR(ret));
+		return ret;
+	}
+
+	ret = i2c_master_recv(ltc2309->client, (char *)&buf, 2);
+	if (ret < 0) {
+		dev_err(ltc2309->dev, "i2c read failed: %pe\n", ERR_PTR(ret));
+		return ret;
+	}
+
+	*val = be16_to_cpu(buf) >> 4;
+
+	return ret;
+}
+
+static int ltc2309_read_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan, int *val,
+			    int *val2, long mask)
+{
+	struct ltc2309 *ltc2309 = iio_priv(indio_dev);
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		mutex_lock(&ltc2309->lock);
+		ret = ltc2309_read_raw_channel(ltc2309, chan->address, val);
+		mutex_unlock(&ltc2309->lock);
+		if (ret < 0)
+			return -EINVAL;
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		*val = ltc2309->vref_mv;
+		*val2 = LTC2309_ADC_RESOLUTION;
+		return IIO_VAL_FRACTIONAL_LOG2;
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct iio_info ltc2309_info = {
+	.read_raw = ltc2309_read_raw,
+};
+
+void ltc2309_regulator_disable(void *regulator)
+{
+	struct regulator *r = (struct regulator *)regulator;
+
+	regulator_disable(r);
+}
+
+static int ltc2309_probe(struct i2c_client *client)
+{
+	struct iio_dev *indio_dev;
+	struct ltc2309 *ltc2309;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*ltc2309));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	ltc2309 = iio_priv(indio_dev);
+	ltc2309->dev = &indio_dev->dev;
+	ltc2309->client = client;
+	ltc2309->vref_mv = 4096; /* Default to the internal ref */
+
+	indio_dev->name = "ltc2309";
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = ltc2309_channels;
+	indio_dev->num_channels = ARRAY_SIZE(ltc2309_channels);
+	indio_dev->info = &ltc2309_info;
+
+	ltc2309->vref = devm_regulator_get_optional(&client->dev, "vref");
+	if (IS_ERR(ltc2309->vref)) {
+		ret = PTR_ERR(ltc2309->vref);
+		if (ret == -ENODEV)
+			ltc2309->vref = NULL;
+		else
+			return ret;
+	}
+
+	if (ltc2309->vref) {
+		ret = regulator_enable(ltc2309->vref);
+		if (ret)
+			return dev_err_probe(ltc2309->dev, ret,
+					     "failed to enable vref\n");
+
+		ret = devm_add_action_or_reset(ltc2309->dev,
+					       ltc2309_regulator_disable,
+					       ltc2309->vref);
+		if (ret) {
+			return dev_err_probe(ltc2309->dev, ret,
+					     "failed to add regulator_disable action: %d\n",
+					     ret);
+			return ret;
+		}
+
+		ret = regulator_get_voltage(ltc2309->vref);
+		if (ret < 0)
+			return ret;
+
+		ltc2309->vref_mv = ret / 1000;
+	}
+
+	mutex_init(&ltc2309->lock);
+
+	return devm_iio_device_register(&client->dev, indio_dev);
+}
+
+static const struct of_device_id ltc2309_of_match[] = {
+	{ .compatible = "lltc,ltc2309" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, ltc2309_of_match);
+
+static const struct i2c_device_id ltc2309_id[] = {
+	{ "ltc2309" },
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, ltc2309_id);
+
+static struct i2c_driver ltc2309_driver = {
+	.driver = {
+		.name = "ltc2309",
+		.of_match_table = ltc2309_of_match,
+	},
+	.probe		= ltc2309_probe,
+	.id_table	= ltc2309_id,
+};
+module_i2c_driver(ltc2309_driver);
+
+MODULE_AUTHOR("Liam Beguin <liambeguin@gmail.com>");
+MODULE_DESCRIPTION("Linear Technology LTC2309 ADC");
+MODULE_LICENSE("GPL v2");

-- 
2.39.0

Re: [PATCH v3 2/2] iio: adc: add ltc2309 support

[kernel test robot]

Hi Liam,

kernel test robot noticed the following build warnings:

[auto build test WARNING on a5e505a99ca748583dbe558b691be1b26f05d678]

url:    https://github.com/intel-lab-lkp/linux/commits/Liam-Beguin/dt-bindings-iio-adc-add-lltc-ltc2309-bindings/20230829-104615
base:   a5e505a99ca748583dbe558b691be1b26f05d678
patch link:    https://lore.kernel.org/r/20230828-ltc2309-v3-2-338b3a8fab8b%40gmail.com
patch subject: [PATCH v3 2/2] iio: adc: add ltc2309 support
config: sparc-allyesconfig (https://download.01.org/0day-ci/archive/20230829/202308291144.r2JZxP9a-lkp@intel.com/config)
compiler: sparc64-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20230829/202308291144.r2JZxP9a-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202308291144.r2JZxP9a-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/iio/adc/ltc2309.c:42: warning: Function parameter or member 'vref_mv' not described in 'ltc2309'


vim +42 drivers/iio/adc/ltc2309.c

    27	
    28	/**
    29	 * struct ltc2309 - internal device data structure
    30	 * @dev:	Device reference
    31	 * @client:	I2C reference
    32	 * @vref:	External reference source
    33	 * @lock:	Lock to serialize data access
    34	 * @vref_mv	Internal voltage reference
    35	 */
    36	struct ltc2309 {
    37		struct device		*dev;
    38		struct i2c_client	*client;
    39		struct regulator	*vref;
    40		struct mutex		lock; /* serialize data access */
    41		int			vref_mv;
  > 42	};
    43	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH v3 2/2] iio: adc: add ltc2309 support

[Jonathan Cameron]

On Mon, 28 Aug 2023 22:41:35 -0400
Liam Beguin <liambeguin@gmail.com> wrote:

> The LTC2309 is an 8-Channel, 12-Bit SAR ADC with an I2C Interface.
> 
> This implements support for all single-ended and differential channels,
> in unipolar mode only.
> 
> Signed-off-by: Liam Beguin <liambeguin@gmail.com>
Hi Liam,

A few really small editorial bits in here.  I'll fix them whilst applying.
Series applied to the togreg branch of iio.git

Note I will be rebasing the tree on rc1 once available and in the meantime
this will only be pushed out as testing.

Thanks,

Jonathan



> +/**
> + * struct ltc2309 - internal device data structure
> + * @dev:	Device reference
> + * @client:	I2C reference
> + * @vref:	External reference source
> + * @lock:	Lock to serialize data access
> + * @vref_mv	Internal voltage reference

Missing : which is what the bot picked up on.

> + */
> +struct ltc2309 {
> +	struct device		*dev;
> +	struct i2c_client	*client;
> +	struct regulator	*vref;
> +	struct mutex		lock; /* serialize data access */
> +	int			vref_mv;
> +};

> +
> +void ltc2309_regulator_disable(void *regulator)
> +{
> +	struct regulator *r = (struct regulator *)regulator;

Never any need to explicitly cast from a void * to any other pointer type.
(C spec says it is always fine to do this :)

Given type is obvious from use, can just do
	regulator_disable(regulator);
and lose the local variable.

> +
> +	regulator_disable(r);
> +}

..
> +
> +static const struct of_device_id ltc2309_of_match[] = {
> +	{ .compatible = "lltc,ltc2309" },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, ltc2309_of_match);
> +
> +static const struct i2c_device_id ltc2309_id[] = {
> +	{ "ltc2309" },
> +	{}

Trivial but space between { and } for consistency.

Re: [PATCH v3 2/2] iio: adc: add ltc2309 support

[Jonathan Cameron]

On Sun, 3 Sep 2023 12:43:41 +0100
Jonathan Cameron <jic23@kernel.org> wrote:

> On Mon, 28 Aug 2023 22:41:35 -0400
> Liam Beguin <liambeguin@gmail.com> wrote:
> 
> > The LTC2309 is an 8-Channel, 12-Bit SAR ADC with an I2C Interface.
> > 
> > This implements support for all single-ended and differential channels,
> > in unipolar mode only.
> > 
> > Signed-off-by: Liam Beguin <liambeguin@gmail.com>  
> Hi Liam,
> 
> A few really small editorial bits in here.  I'll fix them whilst applying.
> Series applied to the togreg branch of iio.git
> 
> Note I will be rebasing the tree on rc1 once available and in the meantime
> this will only be pushed out as testing.

A couple more static analysis reports came in (unreachable return in one pace
and a missing static.  I've fixed up in my tree.

Thanks,

Jonathan

> 
> Thanks,
> 
> Jonathan
> 
> 
> 
> > +/**
> > + * struct ltc2309 - internal device data structure
> > + * @dev:	Device reference
> > + * @client:	I2C reference
> > + * @vref:	External reference source
> > + * @lock:	Lock to serialize data access
> > + * @vref_mv	Internal voltage reference  
> 
> Missing : which is what the bot picked up on.
> 
> > + */
> > +struct ltc2309 {
> > +	struct device		*dev;
> > +	struct i2c_client	*client;
> > +	struct regulator	*vref;
> > +	struct mutex		lock; /* serialize data access */
> > +	int			vref_mv;
> > +};  
> 
> > +
> > +void ltc2309_regulator_disable(void *regulator)
> > +{
> > +	struct regulator *r = (struct regulator *)regulator;  
> 
> Never any need to explicitly cast from a void * to any other pointer type.
> (C spec says it is always fine to do this :)
> 
> Given type is obvious from use, can just do
> 	regulator_disable(regulator);
> and lose the local variable.
> 
> > +
> > +	regulator_disable(r);
> > +}  
> 
> ..
> > +
> > +static const struct of_device_id ltc2309_of_match[] = {
> > +	{ .compatible = "lltc,ltc2309" },
> > +	{ }
> > +};
> > +MODULE_DEVICE_TABLE(of, ltc2309_of_match);
> > +
> > +static const struct i2c_device_id ltc2309_id[] = {
> > +	{ "ltc2309" },
> > +	{}  
> 
> Trivial but space between { and } for consistency.
> 
> 

Re: [PATCH v3 2/2] iio: adc: add ltc2309 support

[Liam Beguin]

Hi Jonathan,

On Sun, Sep 10, 2023 at 03:03:33PM +0100, Jonathan Cameron wrote:
> On Sun, 3 Sep 2023 12:43:41 +0100
> Jonathan Cameron <jic23@kernel.org> wrote:
> 
> > On Mon, 28 Aug 2023 22:41:35 -0400
> > Liam Beguin <liambeguin@gmail.com> wrote:
> > 
> > > The LTC2309 is an 8-Channel, 12-Bit SAR ADC with an I2C Interface.
> > > 
> > > This implements support for all single-ended and differential channels,
> > > in unipolar mode only.
> > > 
> > > Signed-off-by: Liam Beguin <liambeguin@gmail.com>  
> > Hi Liam,
> > 
> > A few really small editorial bits in here.  I'll fix them whilst applying.
> > Series applied to the togreg branch of iio.git
> > 
> > Note I will be rebasing the tree on rc1 once available and in the meantime
> > this will only be pushed out as testing.
> 
> A couple more static analysis reports came in (unreachable return in one pace
> and a missing static.  I've fixed up in my tree.

My apologies for the delay, I was away for a few days.

Thanks for making those changes, I'll go over the comments and the
reports, and if there's anything left, I'll send an update.

> Thanks,
> 
> Jonathan

Thanks again for your time,

Liam

> 
> > 
> > Thanks,
> > 
> > Jonathan
> > 
> > 
> > 
> > > +/**
> > > + * struct ltc2309 - internal device data structure
> > > + * @dev:	Device reference
> > > + * @client:	I2C reference
> > > + * @vref:	External reference source
> > > + * @lock:	Lock to serialize data access
> > > + * @vref_mv	Internal voltage reference  
> > 
> > Missing : which is what the bot picked up on.
> > 
> > > + */
> > > +struct ltc2309 {
> > > +	struct device		*dev;
> > > +	struct i2c_client	*client;
> > > +	struct regulator	*vref;
> > > +	struct mutex		lock; /* serialize data access */
> > > +	int			vref_mv;
> > > +};  
> > 
> > > +
> > > +void ltc2309_regulator_disable(void *regulator)
> > > +{
> > > +	struct regulator *r = (struct regulator *)regulator;  
> > 
> > Never any need to explicitly cast from a void * to any other pointer type.
> > (C spec says it is always fine to do this :)
> > 
> > Given type is obvious from use, can just do
> > 	regulator_disable(regulator);
> > and lose the local variable.
> > 
> > > +
> > > +	regulator_disable(r);
> > > +}  
> > 
> > ..
> > > +
> > > +static const struct of_device_id ltc2309_of_match[] = {
> > > +	{ .compatible = "lltc,ltc2309" },
> > > +	{ }
> > > +};
> > > +MODULE_DEVICE_TABLE(of, ltc2309_of_match);
> > > +
> > > +static const struct i2c_device_id ltc2309_id[] = {
> > > +	{ "ltc2309" },
> > > +	{}  
> > 
> > Trivial but space between { and } for consistency.
> > 
> > 
>