Re: [PATCH net 10/10] net: pse-pd: reject a power limit whose current does not fit an int

[Kory Maincent <kory.maincent@bootlin.com>]

On 10/18/26 10:23, Carlo Szelinsky wrote:
> pse_ethtool_set_pw_limit() turns the power limit into a current as
> mW * 10^9 / uV and stores it in an int. For the largest allowed limit,
> 99900 mW, that overflows below about 46.5 mV. Only 0 V is rejected, and
> si3474 reports the measured voltage of each port. A negative result then
> hits the BUG_ON() in regulator_check_current_limit().
> 
> pse_pi_get_current_limit() does the same conversion and can return a
> wrapped value that looks like an error code.
> 
> Do the conversion in one helper that returns -ERANGE when the result
> does not fit an int.

Same as patch 9. This is not a fix.
Can you send both to net-next instead.
You can add my R-by tag to it.

> Fixes: 4a83abcef5f4 ("net: pse-pd: Add new power limit get and set c33 features")
> Signed-off-by: Carlo Szelinsky <github@szelinsky.de>
> ---
>   drivers/net/pse-pd/pse_core.c | 25 +++++++++++++++----------
>   1 file changed, 15 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/net/pse-pd/pse_core.c b/drivers/net/pse-pd/pse_core.c
> index 0d1e5d5039f8..3e333bef4e48 100644
> --- a/drivers/net/pse-pd/pse_core.c
> +++ b/drivers/net/pse-pd/pse_core.c
> @@ -741,12 +741,19 @@ static int pse_pi_get_voltage(struct regulator_dev *rdev)
>   	return ret;
>   }
>   
> +/* uA = mW * 1000000000 / uV, which does not fit an int for a low uV */
> +static int pse_mw_to_ua(unsigned int mW, int uV)
> +{
> +	u64 uA = DIV_ROUND_CLOSEST_ULL((u64)mW * 1000000000ull, uV);
> +
> +	return uA > INT_MAX ? -ERANGE : uA;
> +}
> +
>   static int pse_pi_get_current_limit(struct regulator_dev *rdev)
>   {
>   	struct pse_controller_dev *pcdev = rdev_get_drvdata(rdev);
>   	const struct pse_controller_ops *ops;
>   	int id, uV, mW, ret;
> -	s64 tmp_64;
>   
>   	ops = pcdev->ops;
>   	id = rdev_get_id(rdev);
> @@ -769,10 +776,7 @@ static int pse_pi_get_current_limit(struct regulator_dev *rdev)
>   		goto out;
>   	uV = ret;
>   
> -	tmp_64 = mW;
> -	tmp_64 *= 1000000000ull;
> -	/* uA = mW * 1000000000 / uV */
> -	ret = DIV_ROUND_CLOSEST_ULL(tmp_64, uV);
> +	ret = pse_mw_to_ua(mW, uV);
>   
>   out:
>   	mutex_unlock(&pcdev->lock);
> @@ -1910,7 +1914,6 @@ int pse_ethtool_set_pw_limit(struct pse_control *psec,
>   {
>   	int uV, uA, ret, previous_pw_allocated = 0;
>   	bool updated;
> -	s64 tmp_64;
>   
>   	if (pw_limit > MAX_PI_PW)
>   		return -ERANGE;
> @@ -1928,10 +1931,12 @@ int pse_ethtool_set_pw_limit(struct pse_control *psec,
>   	}
>   	uV = ret;
>   
> -	tmp_64 = pw_limit;
> -	tmp_64 *= 1000000000ull;
> -	/* uA = mW * 1000000000 / uV */
> -	uA = DIV_ROUND_CLOSEST_ULL(tmp_64, uV);
> +	uA = pse_mw_to_ua(pw_limit, uV);
> +	if (uA < 0) {
> +		NL_SET_ERR_MSG(extack,
> +			       "PSE voltage read is too low to set the limit");
> +		return uA;
> +	}
>   
>   	/* Update power budget only in software power control case and
>   	 * if a Power Device is powered.

-- 
Köry Maincent, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com