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

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Message-ID: <aXiV35CoH6f8FPUT@smile.fi.intel.com>
Date: Tue, 27 Jan 2026 12:39:27 +0200
From: Andy Shevchenko <andriy.shevchenko@...el.com>
To: Oleksij Rempel <o.rempel@...gutronix.de>
Cc: Jonathan Cameron <jic23@...nel.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, kernel@...gutronix.de,
	linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
	devicetree@...r.kernel.org, Andy Shevchenko <andy@...nel.org>,
	David Lechner <dlechner@...libre.com>,
	Nuno Sá <nuno.sa@...log.com>,
	David Jander <david@...tonic.nl>
Subject: Re: [PATCH v2 5/8] iio: dac: ds4424: convert to regmap

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