Introduce a chip_info structure to facilitate adding support for
chip variants with different channel configurations and timing
requirements.

The chip_info structure contains:
- Device name for proper sysfs identification
- Channel specifications and count
- Read delay timing for variants requiring settling time

The ltc2309 struct is modified to store only the read_delay_us value
rather than a pointer to the full chip_info, as this is the only
runtime-accessed field after probe.

This preparatory refactoring does not modify existing LTC2309
functionality.

Signed-off-by: Carlos Jones Jr <carlosjr.jones@analog.com>
---
 drivers/iio/adc/ltc2309.c | 30 +++++++++++++++++++++++++++---
 1 file changed, 27 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/adc/ltc2309.c b/drivers/iio/adc/ltc2309.c
index 5f0d947d0615..0644b1f02568 100644
--- a/drivers/iio/adc/ltc2309.c
+++ b/drivers/iio/adc/ltc2309.c
@@ -8,12 +8,14 @@
  * Copyright (c) 2023, Liam Beguin <liambeguin@gmail.com>
  */
 #include <linux/bitfield.h>
+#include <linux/delay.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>
+#include <linux/array_size.h>
 
 #define LTC2309_ADC_RESOLUTION	12
 #define LTC2309_INTERNAL_REF_MV 4096
@@ -26,18 +28,27 @@
 #define LTC2309_DIN_UNI		BIT(3)
 #define LTC2309_DIN_SLEEP	BIT(2)
 
+struct ltc2309_chip_info {
+	const char *name;
+	unsigned int num_channels;
+	const struct iio_chan_spec *channels __counted_by_ptr(num_channels);
+	unsigned int read_delay_us;
+};
+
 /**
  * struct ltc2309 - internal device data structure
  * @dev:	Device reference
  * @client:	I2C reference
  * @lock:	Lock to serialize data access
  * @vref_mv:	Internal voltage reference
+ * @read_delay_us:	Chip-specific read delay in microseconds
  */
 struct ltc2309 {
 	struct device		*dev;
 	struct i2c_client	*client;
 	struct mutex		lock; /* serialize data access */
 	int			vref_mv;
+	unsigned int		read_delay_us;
 };
 
 /* Order matches expected channel address, See datasheet Table 1. */
@@ -117,6 +128,9 @@ static int ltc2309_read_raw_channel(struct ltc2309 *ltc2309,
 		return ret;
 	}
 
+	if (ltc2309->read_delay_us)
+		fsleep(ltc2309->read_delay_us);
+
 	ret = i2c_master_recv(ltc2309->client, (char *)&buf, 2);
 	if (ret < 0) {
 		dev_err(ltc2309->dev, "i2c read failed: %pe\n", ERR_PTR(ret));
@@ -156,10 +170,18 @@ static const struct iio_info ltc2309_info = {
 	.read_raw = ltc2309_read_raw,
 };
 
+static const struct ltc2309_chip_info ltc2309_chip_info = {
+	.name = "ltc2309",
+	.num_channels = ARRAY_SIZE(ltc2309_channels),
+	.channels = ltc2309_channels,
+};
+
+
 static int ltc2309_probe(struct i2c_client *client)
 {
 	struct iio_dev *indio_dev;
 	struct ltc2309 *ltc2309;
+	const struct ltc2309_chip_info *chip_info;
 	int ret;
 
 	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*ltc2309));
@@ -169,11 +191,13 @@ static int ltc2309_probe(struct i2c_client *client)
 	ltc2309 = iio_priv(indio_dev);
 	ltc2309->dev = &indio_dev->dev;
 	ltc2309->client = client;
+	chip_info = &ltc2309_chip_info;
+	ltc2309->read_delay_us = chip_info->read_delay_us;
 
-	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");
-- 
2.43.0

On Tue, Mar 24, 2026 at 03:13:28PM +0800, Carlos Jones Jr wrote:
> Introduce a chip_info structure to facilitate adding support for
> chip variants with different channel configurations and timing
> requirements.
> 
> The chip_info structure contains:
> - Device name for proper sysfs identification
> - Channel specifications and count
> - Read delay timing for variants requiring settling time
> 
> The ltc2309 struct is modified to store only the read_delay_us value
> rather than a pointer to the full chip_info, as this is the only
> runtime-accessed field after probe.
> 
> This preparatory refactoring does not modify existing LTC2309
> functionality.

...

>  #include <linux/bitfield.h>
> +#include <linux/delay.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>

> +#include <linux/array_size.h>

It starts with 'a'...

...

> +struct ltc2309_chip_info {
> +	const char *name;
> +	unsigned int num_channels;
> +	const struct iio_chan_spec *channels __counted_by_ptr(num_channels);
> +	unsigned int read_delay_us;

Now on some architectures this might have gaps. Have you run `pahole`?
Even if it's fine, I would rather see

	const char *name;
	const struct iio_chan_spec *channels __counted_by_ptr(num_channels);
	unsigned int num_channels;
	unsigned int read_delay_us;

OR (if there are limitations of __counted_by_ptr() attribute)

	const char *name;
	unsigned int read_delay_us;
	unsigned int num_channels;
	const struct iio_chan_spec *channels __counted_by_ptr(num_channels);

> +};

...

> +static const struct ltc2309_chip_info ltc2309_chip_info = {
> +	.name = "ltc2309",
> +	.num_channels = ARRAY_SIZE(ltc2309_channels),
> +	.channels = ltc2309_channels,
> +};
> +
> +

One blank line too many.

...

>  static int ltc2309_probe(struct i2c_client *client)
>  {
>  	struct iio_dev *indio_dev;
>  	struct ltc2309 *ltc2309;
> +	const struct ltc2309_chip_info *chip_info;

Try to preserve reversed xmas tree order.

>  	int ret;

-- 
With Best Regards,
Andy Shevchenko