Re: [PATCH v3 2/2] iio: adc: Add ti-ads1018 driver

[Andy Shevchenko <andriy.shevchenko@intel.com>]

On Fri, Nov 28, 2025 at 10:47:13PM -0500, Kurt Borja wrote:
> Add ti-ads1018 driver for Texas Instruments ADS1018 and ADS1118 SPI
> analog-to-digital converters.
> 
> These chips' MOSI pin is shared with a data-ready interrupt. Defining
> this interrupt in devicetree is optional, therefore we only create an
> IIO trigger if one is found.
> 
> Handling this interrupt requires some considerations. When enabling the
> trigger the CS line is tied low (active), thus we need to hold
> spi_bus_lock() too, to avoid state corruption. This is done inside the
> set_trigger_state() callback, to let users use other triggers without
> wasting a bus lock.

Thank you for the update, my comments below.

...

> +#include <linux/array_size.h>
> +#include <linux/bitfield.h>
> +#include <linux/bitmap.h>

> +#include <linux/byteorder/generic.h>

Must be asm/byteorder.h after the linux/* generic group...

> +#include <linux/dev_printk.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/interrupt.h>
> +#include <linux/math.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/module.h>
> +#include <linux/spi/spi.h>
> +#include <linux/types.h>
> +#include <linux/units.h>
> +

...here

#include <asm/byteorder.h>
+ blank line.

...

> +static void ads1018_set_data_rate_mode(struct ads1018 *ads1018, unsigned int address,
> +				       u8 val)

It's a bit too long.

static void ads1018_set_data_rate_mode(struct ads1018 *ads1018,
				       unsigned int address, u8 val)

...

> +static void ads1018_set_pga_mode(struct ads1018 *ads1018, unsigned int address,
> +				 u8 val)

This is not so, but I would resplit logically, either

static void ads1018_set_pga_mode(struct ads1018 *ads1018, unsigned int address, u8 val)

(however it's significantly longer than 80 limit)

OR

static void ads1018_set_pga_mode(struct ads1018 *ads1018,
				 unsigned int address, u8 val)

(better and consistent with the above).

...

> +/**
> + * ads1018_calc_delay - Calculates an appropriate delay for a single-shot
> + *			reading

Having this on a single line is fine I suppose.

> + * @ad1018: Device data
> + *
> + * Calculates an appropriate delay for a single shot reading, assuming the
> + * device's maximum data-rate is used.
> + *
> + * Context: Expects iio_device_claim_direct() is held.
> + *
> + * Return: Delay in microseconds.

Does 0 have any special meaning?

> + */

...

> +	/* We subtract 10% data-rate error */
> +	hz -= DIV_ROUND_UP(hz, 10);

Hmm... For delays I expect to see adding 10% to have a good margin.

...

> + * Context: Expects spi_bus_lock() is held.

Do we have a lockdep assert for this?

...

> +static int ads1018_read_unlocked(struct ads1018 *ads1018, __be16 *cnv, bool hold_cs)

Hmm... Don't we want to return value in CPU order? I don't know the answer
here, and IIRC IIO triggers might be actually good with endianess conversion
done, if required, in user space.

...

> + * Context: Expects iio_device_claim_direct() is held.

Jonathan et al., do we have lockdep assert available for this?
I really prefer to see the code for it, while comment is good,
it is not good enough.

...

> +static int
> +ads1018_write_raw_unlocked(struct iio_dev *indio_dev, struct iio_chan_spec const *chan,
> +			   int val, int val2, long mask)
> +{
> +	struct ads1018 *ads1018 = iio_priv(indio_dev);
> +	const struct ads1018_chip_info *info = ads1018->chip_info;
> +	unsigned int i;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_SCALE:
> +		for (i = 0; i < info->num_pga_mode_to_gain; i++) {
> +			if (val == info->pga_mode_to_gain[i][0] &&
> +			    val2 == info->pga_mode_to_gain[i][1])
> +				break;
> +		}

> +

You can remove this blank line as the condition is tighten with the for-loop.
But up to you, I'm fine with either.

> +		if (i == info->num_pga_mode_to_gain)
> +			return -EINVAL;
> +
> +		ads1018_set_pga_mode(ads1018, chan->scan_index, i);
> +		return 0;
> +
> +	case IIO_CHAN_INFO_SAMP_FREQ:
> +		for (i = 0; i < info->num_data_rate_mode_to_hz; i++) {
> +			if (val == info->data_rate_mode_to_hz[i])
> +				break;
> +		}

> +

Ditto.

> +		if (i == info->num_data_rate_mode_to_hz)
> +			return -EINVAL;
> +
> +		ads1018_set_data_rate_mode(ads1018, chan->scan_index, i);
> +		return 0;
> +
> +	default:
> +		return -EOPNOTSUPP;
> +	}
> +}

...

> +	if (iio_device_claim_buffer_mode(indio_dev))
> +		goto out_notify_done;
> +
> +	if (iio_trigger_using_own(indio_dev)) {
> +		disable_irq(ads1018->drdy_irq);
> +		ret = ads1018_read_unlocked(ads1018, &scan.conv, true);
> +		enable_irq(ads1018->drdy_irq);
> +	} else {
> +		ret = spi_read(ads1018->spi, ads1018->rx_buf, sizeof(ads1018->rx_buf));
> +		scan.conv = ads1018->rx_buf[0];
> +	}
> +
> +	iio_device_release_buffer_mode(indio_dev);
> +
> +	if (ret)
> +		goto out_notify_done;
> +
> +	iio_push_to_buffers_with_ts(indio_dev, &scan, sizeof(scan), pf->timestamp);
> +
> +out_notify_done:
> +	iio_trigger_notify_done(ads1018->indio_trig);

Jonathan et al., maybe we need an ACQUIRE() class for this? It will solve
the conditional scoped guard case, no?

...

> +static int ads1018_trigger_setup(struct iio_dev *indio_dev)
> +{
> +	struct ads1018 *ads1018 = iio_priv(indio_dev);
> +	struct spi_device *spi = ads1018->spi;
> +	struct device *dev = &spi->dev;
> +	const char *con_id = "drdy";
> +	int ret;
> +
> +	ads1018->drdy_gpiod = devm_gpiod_get_optional(dev, con_id, GPIOD_IN);
> +	if (IS_ERR(ads1018->drdy_gpiod))
> +		return dev_err_probe(dev, PTR_ERR(ads1018->drdy_gpiod),
> +				     "Failed to get %s GPIO.\n", con_id);
> +
> +	/* First try to get IRQ from SPI core, then from GPIO */
> +	if (spi->irq > 0)
> +		ads1018->drdy_irq = spi->irq;
> +	else if (ads1018->drdy_gpiod)
> +		ads1018->drdy_irq = gpiod_to_irq(ads1018->drdy_gpiod);
> +	if (ads1018->drdy_irq < 0)
> +		return dev_err_probe(dev, ads1018->drdy_irq,
> +				     "Failed to get IRQ from %s GPIO.\n", con_id);
> +
> +	/* An IRQ line is only an optional requirement for the IIO trigger */
> +	if (ads1018->drdy_irq == 0)
> +		return 0;
> +
> +	ads1018->indio_trig = devm_iio_trigger_alloc(dev, "%s-dev%d-drdy", indio_dev->name,
> +						     iio_device_id(indio_dev));

	ads1018->indio_trig = devm_iio_trigger_alloc(dev, "%s-dev%d-%s",
						     indio_dev->name,
						     iio_device_id(indio_dev),
						     con_id);

This also will be kept below 80 limit.

> +	if (!ads1018->indio_trig)
> +		return -ENOMEM;
> +
> +	iio_trigger_set_drvdata(ads1018->indio_trig, ads1018);
> +	ads1018->indio_trig->ops = &ads1018_trigger_ops;
> +
> +	ret = devm_iio_trigger_register(dev, ads1018->indio_trig);
> +	if (ret)
> +		return ret;
> +
> +	/*
> +	 * The "data-ready" IRQ line is shared with the MOSI pin, thus we need
> +	 * to keep it disabled until we actually request data.
> +	 */
> +	return devm_request_irq(dev, ads1018->drdy_irq, ads1018_irq_handler,
> +				IRQF_NO_AUTOEN, ads1018->chip_info->name, ads1018);
> +}

...

> +static int ads1018_spi_probe(struct spi_device *spi)
> +{
> +	const struct ads1018_chip_info *info = spi_get_device_match_data(spi);

	struct device *dev = &spi->dev;

> +	struct iio_dev *indio_dev;
> +	struct ads1018 *ads1018;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*ads1018));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	ads1018 = iio_priv(indio_dev);
> +	ads1018->spi = spi;
> +	ads1018->chip_info = info;
> +	spi_set_drvdata(spi, ads1018);
> +
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->name = info->name;
> +	indio_dev->info = &ads1018_iio_info;
> +	indio_dev->channels = info->channels;
> +	indio_dev->num_channels = info->num_channels;
> +
> +	for (unsigned int i = 0; i < ADS1018_CHANNELS_MAX; i++) {
> +		ads1018->chan_data[i].data_rate_mode = ADS1018_DRATE_DEFAULT;
> +		ads1018->chan_data[i].pga_mode = ADS1018_PGA_DEFAULT;
> +	}
> +
> +	ads1018->xfer.rx_buf = ads1018->rx_buf;
> +	ads1018->xfer.len = sizeof(ads1018->rx_buf);
> +	spi_message_init_with_transfers(&ads1018->msg_read, &ads1018->xfer, 1);
> +
> +	ret = ads1018_trigger_setup(indio_dev);
> +	if (ret)
> +		return ret;

> +	ret = devm_iio_triggered_buffer_setup(&spi->dev, indio_dev, iio_pollfunc_store_time,
> +					      ads1018_trigger_handler, &ads1018_buffer_ops);

Too long. With the above done

	ret = devm_iio_triggered_buffer_setup(dev, indio_dev,
					      iio_pollfunc_store_time,
					      ads1018_trigger_handler,
					      &ads1018_buffer_ops);

> +	if (ret)
> +		return ret;
> +
> +	return devm_iio_device_register(&spi->dev, indio_dev);
> +}

...

> +/**
> + * ADS1018_FSR_TO_SCALE - Converts FSR into scale
> + * @_fsr: Full-scale range in millivolts
> + * @_res: ADC resolution

Add here something like this:

*
* The macro is crafted to avoid potential overflows on 32-bit machines.
* This imposes restrictions to the possible values for @_fsr (less
* than 274878), and @_res (great or equal to 6 bits).
*

> + * Return: Scale in IIO_VAL_INT_PLUS_NANO format
> + */
> +#define ADS1018_FSR_TO_SCALE(_fsr, _res) \
> +	{ 0, ((_fsr) * (MICRO >> 6)) / BIT((_res) - 6) }

-- 
With Best Regards,
Andy Shevchenko