[PATCH 0/2] iio: adc: ltc2309: add support driver for ltc2305

[PATCH 0/2] iio: adc: ltc2309: add support driver for ltc2305

[Kyle Hsieh]

The series add support for ltc2305 controller from 
Linear Technology Corporation(lltc).
This is low noise, low power, 2 channels 12-bit successive
approximation ADCs.

Signed-off-by: Kyle Hsieh <kylehsieh1995@gmail.com>
---
Kyle Hsieh (2):
      dt-bindings: adc: ltc2497: add support for ltc2305
      iio: adc: ltc2309: add support for ltc2305

 .../devicetree/bindings/iio/adc/lltc,ltc2497.yaml  |  7 +++
 drivers/iio/adc/ltc2309.c                          | 50 ++++++++++++++++++++--
 2 files changed, 53 insertions(+), 4 deletions(-)
---
base-commit: 9448598b22c50c8a5bb77a9103e2d49f134c9578
change-id: 20251223-add_ltc2305_driver-728fa9161bc7

Best regards,
-- 
Kyle Hsieh <kylehsieh1995@gmail.com>

[PATCH 1/2] dt-bindings: adc: ltc2497: add support for ltc2305

[Kyle Hsieh]

Add documentation for the 2-channel LTC2305 ADC in the
existing ltc2497 binding.
This enables automatic device tree matching for LTC2305
while using the LTC2309 driver (drivers/iio/adc/ltc2309.c),
since both ADCs share the same I2C interface and 12-bit SAR architecture.
The main difference is the number of channels (LTC2305: 2, LTC2309: 8).

Signed-off-by: Kyle Hsieh <kylehsieh1995@gmail.com>
---
 Documentation/devicetree/bindings/iio/adc/lltc,ltc2497.yaml | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Documentation/devicetree/bindings/iio/adc/lltc,ltc2497.yaml b/Documentation/devicetree/bindings/iio/adc/lltc,ltc2497.yaml
index 5cc6a9684077..c884b6e03767 100644
--- a/Documentation/devicetree/bindings/iio/adc/lltc,ltc2497.yaml
+++ b/Documentation/devicetree/bindings/iio/adc/lltc,ltc2497.yaml
@@ -11,6 +11,12 @@ maintainers:
   - Liam Beguin <liambeguin@gmail.com>
 
 description: |
+  LTC2305:
+    low noise, low power, 2-channel, 12-bit successive approximation ADC with an
+    I2C compatible serial interface.
+
+    https://www.analog.com/media/en/technical-documentation/data-sheets/23015fb.pdf
+
   LTC2309:
     low noise, low power, 8-channel, 12-bit successive approximation ADC with an
     I2C compatible serial interface.
@@ -28,6 +34,7 @@ description: |
 properties:
   compatible:
     enum:
+      - lltc,ltc2305
       - lltc,ltc2309
       - lltc,ltc2497
       - lltc,ltc2499

-- 
2.34.1

[PATCH 2/2] iio: adc: ltc2309: add support for ltc2305

[Kyle Hsieh]

Add support for the 2-channel LTC2305 ADC in the existing LTC2309 driver.
The LTC2305 and LTC2309 share similar features: both are 12-bit,
low-noise, low-power SAR ADCs with an I2C interface.
The main difference is the number of channels: LTC2305 has 2 channels,
while LTC2309 has 8 channels.

Signed-off-by: Kyle Hsieh <kylehsieh1995@gmail.com>
---
 drivers/iio/adc/ltc2309.c | 50 +++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 46 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/adc/ltc2309.c b/drivers/iio/adc/ltc2309.c
index 5f0d947d0615..7a611ddd00d2 100644
--- a/drivers/iio/adc/ltc2309.c
+++ b/drivers/iio/adc/ltc2309.c
@@ -1,9 +1,11 @@
 // SPDX-License-Identifier: GPL-2.0
 /*
  * The LTC2309 is an 8-Channel, 12-Bit SAR ADC with an I2C Interface.
+ * The LTC2305 is a  2-Channel, 12-Bit SAR ADC with an I2C Interface.
  *
  * Datasheet:
  * https://www.analog.com/media/en/technical-documentation/data-sheets/2309fd.pdf
+ * https://www.analog.com/media/en/technical-documentation/data-sheets/23015fb.pdf
  *
  * Copyright (c) 2023, Liam Beguin <liambeguin@gmail.com>
  */
@@ -60,6 +62,13 @@ enum ltc2309_channels {
 	LTC2309_CH7,
 };
 
+enum ltc2305_channels {
+	LTC2305_CH0_CH1 = 0,
+	LTC2305_CH1_CH0,
+	LTC2305_CH0,
+	LTC2305_CH1,
+};
+
 #define LTC2309_CHAN(_chan, _addr) {				\
 	.type = IIO_VOLTAGE,					\
 	.indexed = 1,						\
@@ -99,6 +108,31 @@ static const struct iio_chan_spec ltc2309_channels[] = {
 	LTC2309_DIFF_CHAN(7, 6, LTC2309_CH7_CH6),
 };
 
+static const struct iio_chan_spec ltc2305_channels[] = {
+	LTC2309_CHAN(0, LTC2305_CH0),
+	LTC2309_CHAN(1, LTC2305_CH1),
+	LTC2309_DIFF_CHAN(0, 1, LTC2305_CH0_CH1),
+	LTC2309_DIFF_CHAN(1, 0, LTC2305_CH1_CH0),
+};
+
+struct ltc230x_chip_info {
+	const char *name;
+	const struct iio_chan_spec *channels;
+	int num_channels;
+};
+
+static const struct ltc230x_chip_info ltc2309_chip_info = {
+	.name = "ltc2309",
+	.channels = ltc2309_channels,
+	.num_channels = ARRAY_SIZE(ltc2309_channels),
+};
+
+static const struct ltc230x_chip_info ltc2305_chip_info = {
+	.name = "ltc2305",
+	.channels = ltc2305_channels,
+	.num_channels = ARRAY_SIZE(ltc2305_channels),
+};
+
 static int ltc2309_read_raw_channel(struct ltc2309 *ltc2309,
 				    unsigned long address, int *val)
 {
@@ -158,6 +192,8 @@ static const struct iio_info ltc2309_info = {
 
 static int ltc2309_probe(struct i2c_client *client)
 {
+	const struct of_device_id *match;
+	const struct ltc230x_chip_info *chip_info;
 	struct iio_dev *indio_dev;
 	struct ltc2309 *ltc2309;
 	int ret;
@@ -167,13 +203,17 @@ static int ltc2309_probe(struct i2c_client *client)
 		return -ENOMEM;
 
 	ltc2309 = iio_priv(indio_dev);
+	chip_info = device_get_match_data(&client->dev);
+	if (!chip_info)
+		return -EINVAL;
+
 	ltc2309->dev = &indio_dev->dev;
 	ltc2309->client = client;
 
-	indio_dev->name = "ltc2309";
+	indio_dev->name = chip_info->name;
 	indio_dev->modes = INDIO_DIRECT_MODE;
-	indio_dev->channels = ltc2309_channels;
-	indio_dev->num_channels = ARRAY_SIZE(ltc2309_channels);
+	indio_dev->channels = chip_info->channels;
+	indio_dev->num_channels = chip_info->num_channels;
 	indio_dev->info = &ltc2309_info;
 
 	ret = devm_regulator_get_enable_read_voltage(&client->dev, "vref");
@@ -189,13 +229,15 @@ static int ltc2309_probe(struct i2c_client *client)
 }
 
 static const struct of_device_id ltc2309_of_match[] = {
-	{ .compatible = "lltc,ltc2309" },
+	{ .compatible = "lltc,ltc2309", .data = &ltc2309_chip_info },
+	{ .compatible = "lltc,ltc2305", .data = &ltc2305_chip_info },
 	{ }
 };
 MODULE_DEVICE_TABLE(of, ltc2309_of_match);
 
 static const struct i2c_device_id ltc2309_id[] = {
 	{ "ltc2309" },
+	{ "ltc2305" },
 	{ }
 };
 MODULE_DEVICE_TABLE(i2c, ltc2309_id);

-- 
2.34.1

Re: [PATCH 2/2] iio: adc: ltc2309: add support for ltc2305

[David Lechner]

On 12/23/25 3:12 AM, Kyle Hsieh wrote:
> Add support for the 2-channel LTC2305 ADC in the existing LTC2309 driver.
> The LTC2305 and LTC2309 share similar features: both are 12-bit,
> low-noise, low-power SAR ADCs with an I2C interface.
> The main difference is the number of channels: LTC2305 has 2 channels,
> while LTC2309 has 8 channels.
> 
> Signed-off-by: Kyle Hsieh <kylehsieh1995@gmail.com>
> ---
>  drivers/iio/adc/ltc2309.c | 50 +++++++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 46 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iio/adc/ltc2309.c b/drivers/iio/adc/ltc2309.c
> index 5f0d947d0615..7a611ddd00d2 100644
> --- a/drivers/iio/adc/ltc2309.c
> +++ b/drivers/iio/adc/ltc2309.c
> @@ -1,9 +1,11 @@
>  // SPDX-License-Identifier: GPL-2.0
>  /*
>   * The LTC2309 is an 8-Channel, 12-Bit SAR ADC with an I2C Interface.
> + * The LTC2305 is a  2-Channel, 12-Bit SAR ADC with an I2C Interface.

Would be more conventional to list things in low to high order like in the
dt-bindings. (same applies throughout this patch)

>   *
>   * Datasheet:
>   * https://www.analog.com/media/en/technical-documentation/data-sheets/2309fd.pdf
> + * https://www.analog.com/media/en/technical-documentation/data-sheets/23015fb.pdf
>   *
>   * Copyright (c) 2023, Liam Beguin <liambeguin@gmail.com>
>   */
> @@ -60,6 +62,13 @@ enum ltc2309_channels {
>  	LTC2309_CH7,
>  };
>  
> +enum ltc2305_channels {
> +	LTC2305_CH0_CH1 = 0,

Initializer is not strictly needed. I guess it is consistent with the
existing code though, so OK.

> +	LTC2305_CH1_CH0,
> +	LTC2305_CH0,
> +	LTC2305_CH1,
> +};
> +
>  #define LTC2309_CHAN(_chan, _addr) {				\
>  	.type = IIO_VOLTAGE,					\
>  	.indexed = 1,						\
> @@ -99,6 +108,31 @@ static const struct iio_chan_spec ltc2309_channels[] = {
>  	LTC2309_DIFF_CHAN(7, 6, LTC2309_CH7_CH6),
>  };
>  
> +static const struct iio_chan_spec ltc2305_channels[] = {
> +	LTC2309_CHAN(0, LTC2305_CH0),
> +	LTC2309_CHAN(1, LTC2305_CH1),
> +	LTC2309_DIFF_CHAN(0, 1, LTC2305_CH0_CH1),
> +	LTC2309_DIFF_CHAN(1, 0, LTC2305_CH1_CH0),
> +};
> +
> +struct ltc230x_chip_info {

We avoid putting "x" in names like this because the pattern breaks too often.
Just use the main driver prefix of ltc2309.

> +	const char *name;
> +	const struct iio_chan_spec *channels;
> +	int num_channels;
> +};
> +
> +static const struct ltc230x_chip_info ltc2309_chip_info = {
> +	.name = "ltc2309",
> +	.channels = ltc2309_channels,
> +	.num_channels = ARRAY_SIZE(ltc2309_channels),
> +};
> +
> +static const struct ltc230x_chip_info ltc2305_chip_info = {
> +	.name = "ltc2305",
> +	.channels = ltc2305_channels,
> +	.num_channels = ARRAY_SIZE(ltc2305_channels),
> +};
> +
>  static int ltc2309_read_raw_channel(struct ltc2309 *ltc2309,
>  				    unsigned long address, int *val)
>  {
> @@ -158,6 +192,8 @@ static const struct iio_info ltc2309_info = {
>  
>  static int ltc2309_probe(struct i2c_client *client)
>  {
> +	const struct of_device_id *match;

Unused?

> +	const struct ltc230x_chip_info *chip_info;
>  	struct iio_dev *indio_dev;
>  	struct ltc2309 *ltc2309;
>  	int ret;
> @@ -167,13 +203,17 @@ static int ltc2309_probe(struct i2c_client *client)
>  		return -ENOMEM;
>  
>  	ltc2309 = iio_priv(indio_dev);
> +	chip_info = device_get_match_data(&client->dev);

Why not i2c_get_match_data()?

> +	if (!chip_info)
> +		return -EINVAL;
> +
>  	ltc2309->dev = &indio_dev->dev;
>  	ltc2309->client = client;
>  
> -	indio_dev->name = "ltc2309";
> +	indio_dev->name = chip_info->name;
>  	indio_dev->modes = INDIO_DIRECT_MODE;
> -	indio_dev->channels = ltc2309_channels;
> -	indio_dev->num_channels = ARRAY_SIZE(ltc2309_channels);
> +	indio_dev->channels = chip_info->channels;
> +	indio_dev->num_channels = chip_info->num_channels;
>  	indio_dev->info = &ltc2309_info;
>  
>  	ret = devm_regulator_get_enable_read_voltage(&client->dev, "vref");
> @@ -189,13 +229,15 @@ static int ltc2309_probe(struct i2c_client *client)
>  }
>  
>  static const struct of_device_id ltc2309_of_match[] = {
> -	{ .compatible = "lltc,ltc2309" },
> +	{ .compatible = "lltc,ltc2309", .data = &ltc2309_chip_info },
> +	{ .compatible = "lltc,ltc2305", .data = &ltc2305_chip_info },
>  	{ }
>  };
>  MODULE_DEVICE_TABLE(of, ltc2309_of_match);
>  
>  static const struct i2c_device_id ltc2309_id[] = {
>  	{ "ltc2309" },
> +	{ "ltc2305" },

Also need to add chip_infos here.

>  	{ }
>  };
>  MODULE_DEVICE_TABLE(i2c, ltc2309_id);
> 

Re: [PATCH 2/2] iio: adc: ltc2309: add support for ltc2305

[Kyle Hsieh]

On Wed, Dec 24, 2025 at 2:38 AM David Lechner <dlechner@baylibre.com> wrote:
>
> On 12/23/25 3:12 AM, Kyle Hsieh wrote:
> > Add support for the 2-channel LTC2305 ADC in the existing LTC2309 driver.
> > The LTC2305 and LTC2309 share similar features: both are 12-bit,
> > low-noise, low-power SAR ADCs with an I2C interface.
> > The main difference is the number of channels: LTC2305 has 2 channels,
> > while LTC2309 has 8 channels.
> >
> > Signed-off-by: Kyle Hsieh <kylehsieh1995@gmail.com>
> > ---
> >  drivers/iio/adc/ltc2309.c | 50 +++++++++++++++++++++++++++++++++++++++++++----
> >  1 file changed, 46 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/iio/adc/ltc2309.c b/drivers/iio/adc/ltc2309.c
> > index 5f0d947d0615..7a611ddd00d2 100644
> > --- a/drivers/iio/adc/ltc2309.c
> > +++ b/drivers/iio/adc/ltc2309.c
> > @@ -1,9 +1,11 @@
> >  // SPDX-License-Identifier: GPL-2.0
> >  /*
> >   * The LTC2309 is an 8-Channel, 12-Bit SAR ADC with an I2C Interface.
> > + * The LTC2305 is a  2-Channel, 12-Bit SAR ADC with an I2C Interface.
>
> Would be more conventional to list things in low to high order like in the
> dt-bindings. (same applies throughout this patch)
>
I will reorder descriptions and definitions to list devices in
low-to-high order.
> >   *
> >   * Datasheet:
> >   * https://www.analog.com/media/en/technical-documentation/data-sheets/2309fd.pdf
> > + * https://www.analog.com/media/en/technical-documentation/data-sheets/23015fb.pdf
> >   *
> >   * Copyright (c) 2023, Liam Beguin <liambeguin@gmail.com>
> >   */
> > @@ -60,6 +62,13 @@ enum ltc2309_channels {
> >       LTC2309_CH7,
> >  };
> >
> > +enum ltc2305_channels {
> > +     LTC2305_CH0_CH1 = 0,
>
> Initializer is not strictly needed. I guess it is consistent with the
> existing code though, so OK.
>
> > +     LTC2305_CH1_CH0,
> > +     LTC2305_CH0,
> > +     LTC2305_CH1,
> > +};
> > +
> >  #define LTC2309_CHAN(_chan, _addr) {                         \
> >       .type = IIO_VOLTAGE,                                    \
> >       .indexed = 1,                                           \
> > @@ -99,6 +108,31 @@ static const struct iio_chan_spec ltc2309_channels[] = {
> >       LTC2309_DIFF_CHAN(7, 6, LTC2309_CH7_CH6),
> >  };
> >
> > +static const struct iio_chan_spec ltc2305_channels[] = {
> > +     LTC2309_CHAN(0, LTC2305_CH0),
> > +     LTC2309_CHAN(1, LTC2305_CH1),
> > +     LTC2309_DIFF_CHAN(0, 1, LTC2305_CH0_CH1),
> > +     LTC2309_DIFF_CHAN(1, 0, LTC2305_CH1_CH0),
> > +};
> > +
> > +struct ltc230x_chip_info {
>
> We avoid putting "x" in names like this because the pattern breaks too often.
> Just use the main driver prefix of ltc2309.
>
Got it, I will replace this 'ltc203x' with 'ltc2309'.
> > +     const char *name;
> > +     const struct iio_chan_spec *channels;
> > +     int num_channels;
> > +};
> > +
> > +static const struct ltc230x_chip_info ltc2309_chip_info = {
> > +     .name = "ltc2309",
> > +     .channels = ltc2309_channels,
> > +     .num_channels = ARRAY_SIZE(ltc2309_channels),
> > +};
> > +
> > +static const struct ltc230x_chip_info ltc2305_chip_info = {
> > +     .name = "ltc2305",
> > +     .channels = ltc2305_channels,
> > +     .num_channels = ARRAY_SIZE(ltc2305_channels),
> > +};
> > +
> >  static int ltc2309_read_raw_channel(struct ltc2309 *ltc2309,
> >                                   unsigned long address, int *val)
> >  {
> > @@ -158,6 +192,8 @@ static const struct iio_info ltc2309_info = {
> >
> >  static int ltc2309_probe(struct i2c_client *client)
> >  {
> > +     const struct of_device_id *match;
>
> Unused?
>
I will remove in v2.
> > +     const struct ltc230x_chip_info *chip_info;
> >       struct iio_dev *indio_dev;
> >       struct ltc2309 *ltc2309;
> >       int ret;
> > @@ -167,13 +203,17 @@ static int ltc2309_probe(struct i2c_client *client)
> >               return -ENOMEM;
> >
> >       ltc2309 = iio_priv(indio_dev);
> > +     chip_info = device_get_match_data(&client->dev);
>
> Why not i2c_get_match_data()?
>
I will switch from device_get_match_data() to i2c_get_match_data() in v2
> > +     if (!chip_info)
> > +             return -EINVAL;
> > +
> >       ltc2309->dev = &indio_dev->dev;
> >       ltc2309->client = client;
> >
> > -     indio_dev->name = "ltc2309";
> > +     indio_dev->name = chip_info->name;
> >       indio_dev->modes = INDIO_DIRECT_MODE;
> > -     indio_dev->channels = ltc2309_channels;
> > -     indio_dev->num_channels = ARRAY_SIZE(ltc2309_channels);
> > +     indio_dev->channels = chip_info->channels;
> > +     indio_dev->num_channels = chip_info->num_channels;
> >       indio_dev->info = &ltc2309_info;
> >
> >       ret = devm_regulator_get_enable_read_voltage(&client->dev, "vref");
> > @@ -189,13 +229,15 @@ static int ltc2309_probe(struct i2c_client *client)
> >  }
> >
> >  static const struct of_device_id ltc2309_of_match[] = {
> > -     { .compatible = "lltc,ltc2309" },
> > +     { .compatible = "lltc,ltc2309", .data = &ltc2309_chip_info },
> > +     { .compatible = "lltc,ltc2305", .data = &ltc2305_chip_info },
> >       { }
> >  };
> >  MODULE_DEVICE_TABLE(of, ltc2309_of_match);
> >
> >  static const struct i2c_device_id ltc2309_id[] = {
> >       { "ltc2309" },
> > +     { "ltc2305" },
>
> Also need to add chip_infos here.
>
Thanks reminder, I will add.
> >       { }
> >  };
> >  MODULE_DEVICE_TABLE(i2c, ltc2309_id);
> >
>

Re: [PATCH 2/2] iio: adc: ltc2309: add support for ltc2305

[kernel test robot]

Hi Kyle,

kernel test robot noticed the following build warnings:

[auto build test WARNING on 9448598b22c50c8a5bb77a9103e2d49f134c9578]

url:    https://github.com/intel-lab-lkp/linux/commits/Kyle-Hsieh/dt-bindings-adc-ltc2497-add-support-for-ltc2305/20251223-171509
base:   9448598b22c50c8a5bb77a9103e2d49f134c9578
patch link:    https://lore.kernel.org/r/20251223-add_ltc2305_driver-v1-2-dfa0827fd620%40gmail.com
patch subject: [PATCH 2/2] iio: adc: ltc2309: add support for ltc2305
config: sparc64-randconfig-001-20251224 (https://download.01.org/0day-ci/archive/20251224/202512240416.ckqhNpHO-lkp@intel.com/config)
compiler: sparc64-linux-gcc (GCC) 8.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251224/202512240416.ckqhNpHO-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/202512240416.ckqhNpHO-lkp@intel.com/

All warnings (new ones prefixed by >>):

   drivers/iio/adc/ltc2309.c: In function 'ltc2309_probe':
>> drivers/iio/adc/ltc2309.c:195:29: warning: unused variable 'match' [-Wunused-variable]
     const struct of_device_id *match;
                                ^~~~~


vim +/match +195 drivers/iio/adc/ltc2309.c

   192	
   193	static int ltc2309_probe(struct i2c_client *client)
   194	{
 > 195		const struct of_device_id *match;
   196		const struct ltc230x_chip_info *chip_info;
   197		struct iio_dev *indio_dev;
   198		struct ltc2309 *ltc2309;
   199		int ret;
   200	
   201		indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*ltc2309));
   202		if (!indio_dev)
   203			return -ENOMEM;
   204	
   205		ltc2309 = iio_priv(indio_dev);
   206		chip_info = device_get_match_data(&client->dev);
   207		if (!chip_info)
   208			return -EINVAL;
   209	
   210		ltc2309->dev = &indio_dev->dev;
   211		ltc2309->client = client;
   212	
   213		indio_dev->name = chip_info->name;
   214		indio_dev->modes = INDIO_DIRECT_MODE;
   215		indio_dev->channels = chip_info->channels;
   216		indio_dev->num_channels = chip_info->num_channels;
   217		indio_dev->info = &ltc2309_info;
   218	
   219		ret = devm_regulator_get_enable_read_voltage(&client->dev, "vref");
   220		if (ret < 0 && ret != -ENODEV)
   221			return dev_err_probe(ltc2309->dev, ret,
   222					     "failed to get vref voltage\n");
   223	
   224		ltc2309->vref_mv = ret == -ENODEV ? LTC2309_INTERNAL_REF_MV : ret / 1000;
   225	
   226		mutex_init(&ltc2309->lock);
   227	
   228		return devm_iio_device_register(&client->dev, indio_dev);
   229	}
   230	

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