Re: [PATCH v2 5/8] iio: dac: ds4424: convert to regmap

Andy Shevchenko
2026-01-27T10:39:33Z

On Tue, Jan 27, 2026 at 07:09:36AM +0100, Oleksij Rempel wrote:
> Refactor the driver to use the regmap API.
>
> Replace the driver-specific mutex and manual shadow buffers with the
> standard regmap infrastructure for locking and caching.
>
> This ensures the cache is populated from hardware at probe, preventing
> state desynchronization (e.g. across suspend/resume).
>
> Define access tables to validate the different register maps of DS44x2
> and DS44x4.

...

> +static const struct regmap_access_table ds44x4_table = {
> + .yes_ranges = ds44x4_ranges,
> + .n_yes_ranges = ARRAY_SIZE(ds44x4_ranges),

+ array_size.h

> +};

...

> + ret = regmap_read(data->regmap, DS4424_DAC_ADDR(chan->channel),
> + &regval);
> if (ret < 0) {
> - pr_err("%s : ds4424_get_value returned %d\n",
> - __func__, ret);
> + pr_err("%s : regmap_read returned %d\n",
> + __func__, ret);

This should be dev_err() to begin with. Perhaps you want a new patch for that.

> return ret;
> }

...

> + /* Bulk read all channels starting at 0xf8.
> + * This populates the regmap cache with current HW values.
> + */

/*
* Use proper style for multi-line
* comments.
*/

...

> + if (ret)
> + return dev_err_probe(&indio_dev->dev, ret, "Failed to seed cache\n");

Why not physical device? I assume during probe we use physical device, when we
do IIO callbacks, we use IIO device.

...

> static int ds4424_suspend(struct device *dev)
> {
> + struct iio_dev *indio_dev = dev_get_drvdata(dev);
> struct ds4424_data *data = iio_priv(indio_dev);
> + int ret;
> +
> + /* Disable all outputs, bypass cache so the '0' isn't saved */
> + regcache_cache_bypass(data->regmap, true);
> + for (unsigned int i = 0; i < indio_dev->num_channels; i++) {
> + ret = regmap_write(data->regmap, DS4424_DAC_ADDR(i), 0);
> + if (ret) {
> + dev_err(dev, "Failed to zero channel %d: %d\n", i, ret);

%u for 'i'.

> + regcache_cache_bypass(data->regmap, false);
> return ret;
> + }
> }
> + regcache_cache_bypass(data->regmap, false);
> +
> + regcache_cache_only(data->regmap, true);
> + regcache_mark_dirty(data->regmap);
> +
> + return 0;
> }

...

> usleep_range(1000, 1200);

Side note: Perhaps fsleep() in the future...

> + ret = ds4424_init_regmap(client, indio_dev);
> + if (ret < 0)

Do we need ' < 0' part?

> + goto fail;
> +
> + ret = ds4424_verify_chip(indio_dev);
> + if (ret < 0)

Ditto.

> + goto fail;

--
With Best Regards,
Andy Shevchenko