linux-kernel - Re: [PATCH v3] staging: iio: ad5933: Correct settling cycles encoding per datasheet

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Message-ID: <ce0c0684-2f5e-4e23-824e-8bcad56e6b0c@stanley.mountain>
Date: Tue, 22 Apr 2025 13:02:27 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Gabriel Shahrouzi <gshahrouzi@...il.com>
Cc: gregkh@...uxfoundation.org, jic23@...nel.org, lars@...afoo.de,
	linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-staging@...ts.linux.dev, Michael.Hennerich@...log.com,
	skhan@...uxfoundation.org, linux-kernel-mentees@...ts.linux.dev,
	stable@...r.kernel.org
Subject: Re: [PATCH v3] staging: iio: ad5933: Correct settling cycles
 encoding per datasheet

On Sat, Apr 19, 2025 at 08:30:00PM -0400, Gabriel Shahrouzi wrote:
> Implement the settling cycles encoding as specified in the AD5933
> datasheet, Table 13 ("Number of Settling Times Cycles Register"). The
> previous logic did not correctly translate the user-requested effective
> cycle count into the required 9-bit base + 2-bit multiplier format
> (D10..D0) for values exceeding 511.
> 
> Clamp the user input for out_altvoltage0_settling_cycles to the
> maximum effective value of 2044 cycles (511 * 4x multiplier).
> 
> Fixes: f94aa354d676 ("iio: impedance-analyzer: New driver for AD5933/4 Impedance Converter, Network Analyzer")
> Cc: stable@...r.kernel.org
> Signed-off-by: Gabriel Shahrouzi <gshahrouzi@...il.com>
> ---
> Changes in v3:
> 	- Only include fix (remove refactoring which will be its own
> 	  separate patch).
> Changes in v2:
>         - Fix spacing in comment around '+'.
>         - Define mask and values for settling cycle multipliers.
> ---
>  drivers/staging/iio/impedance-analyzer/ad5933.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/iio/impedance-analyzer/ad5933.c b/drivers/staging/iio/impedance-analyzer/ad5933.c
> index d5544fc2fe989..f8fcc10ea8150 100644
> --- a/drivers/staging/iio/impedance-analyzer/ad5933.c
> +++ b/drivers/staging/iio/impedance-analyzer/ad5933.c
> @@ -411,7 +411,7 @@ static ssize_t ad5933_store(struct device *dev,
>  		ret = ad5933_cmd(st, 0);
>  		break;
>  	case AD5933_OUT_SETTLING_CYCLES:
> -		val = clamp(val, (u16)0, (u16)0x7FF);
> +		val = clamp(val, (u16)0, (u16)0x7FC);

We have a fancy clamp() define now so the ugly casts are no longer
required.

regards,
dan carpenter