Re: [PATCH] iio: potentiostat: lmp91000: Handle configuration write errors

[Andy Shevchenko]

On Thu, Nov 12, 2026 at 03:17:47PM +0800, Zhu Jun wrote:
> lmp91000_read_config() ignores errors when unlocking and programming
> the TIA and reference registers. Probe can then succeed even though
> the hardware configuration does not match the parameters used to
> interpret measurements.
> 
> Check the configuration writes and return the first error. After a
> successful unlock, attempt to restore write protection even if a
> configuration write fails, and report a relock failure as well.

...

> static int lmp91000_read_config(struct lmp91000_data *data)
>  {
>  	struct device *dev = data->dev;
>  	unsigned int reg, val;
> -	int i, ret;
> +	int i, ret, lock_ret;

While at it, it's better to split semantically different variables:

	int ret, lock_ret;
	int i;

> +	ret = regmap_write(data->regmap, LMP91000_REG_TIACN, reg);
> +	if (!ret)
> +		ret = regmap_write(data->regmap, LMP91000_REG_REFCN,
> +				   LMP91000_REG_REFCN_EXT_REF | LMP91000_REG_REFCN_50_ZERO);
> +
> +	/* Restore write protection even if programming the registers failed. */
> +	lock_ret = regmap_write(data->regmap, LMP91000_REG_LOCK, 1);
> +
> +	return ret ? ret : lock_ret;

It doesn't use any guard()() or so, hence just make a goto instead
(and use Elvis):

	ret = regmap_write(data->regmap, LMP91000_REG_TIACN, reg);
	if (ret)
		goto restore_lock;

	ret = regmap_write(data->regmap, LMP91000_REG_REFCN,
			   LMP91000_REG_REFCN_EXT_REF | LMP91000_REG_REFCN_50_ZERO);

restore_lock:

	/* Restore write protection even if programming the registers failed. */
	lock_ret = regmap_write(data->regmap, LMP91000_REG_LOCK, 1);

	return ret ?: lock_ret;

>  }

Alternatively, wrap the existing function (this will make code cleaner in some
maintainer's opinion).

...

In any case there is a question how may the caller distinguish the error from
register write and from the lock restoration? And what will it do in either of
the cases?

-- 
With Best Regards,
Andy Shevchenko