linux-kernel - Re: [PATCH] power: supply: ingenic: Fix some error handling paths in ingenic_battery_get

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Date: Sun, 23 Jun 2024 13:26:38 +0200
From: Artur Rojek <contact@...ur-rojek.eu>
To: Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc: Paul Cercueil <paul@...pouillou.net>, Sebastian Reichel
 <sre@...nel.org>, Jonathan Cameron <Jonathan.Cameron@...wei.com>,
 linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org, Sebastian
 Reichel <sebastian.reichel@...labora.com>, linux-mips@...r.kernel.org,
 linux-pm@...r.kernel.org
Subject: Re: [PATCH] power: supply: ingenic: Fix some error handling paths in
 ingenic_battery_get_property()

Hi Christophe,

thanks for the patch, looking good.

Acked-by: Artur Rojek <contact@...ur-rojek.eu>

Cheers,
Artur

On 2024-06-23 07:50, Christophe JAILLET wrote:
> If iio_read_channel_processed() fails, 'val->intval' is not updated, 
> but it
> is still *1000 just after. So, in case of error, the *1000 accumulate 
> and
> 'val->intval' becomes erroneous.
> 
> So instead of rescaling the value after the fact, use the dedicated 
> scaling
> API. This way the result is updated only when needed. In case of error, 
> the
> previous value is kept, unmodified.
> 
> This should also reduce any inaccuracies resulting from the scaling.
> 
> Finally, this is also slightly more efficient as it saves a function 
> call
> and a multiplication.
> 
> Fixes: fb24ccfbe1e0 ("power: supply: add Ingenic JZ47xx battery 
> driver.")
> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> ---
>  drivers/power/supply/ingenic-battery.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/power/supply/ingenic-battery.c 
> b/drivers/power/supply/ingenic-battery.c
> index 2e7fdfde47ec..0a40f425c277 100644
> --- a/drivers/power/supply/ingenic-battery.c
> +++ b/drivers/power/supply/ingenic-battery.c
> @@ -31,8 +31,9 @@ static int ingenic_battery_get_property(struct 
> power_supply *psy,
> 
>  	switch (psp) {
>  	case POWER_SUPPLY_PROP_HEALTH:
> -		ret = iio_read_channel_processed(bat->channel, &val->intval);
> -		val->intval *= 1000;
> +		ret = iio_read_channel_processed_scale(bat->channel,
> +						       &val->intval,
> +						       1000);
>  		if (val->intval < info->voltage_min_design_uv)
>  			val->intval = POWER_SUPPLY_HEALTH_DEAD;
>  		else if (val->intval > info->voltage_max_design_uv)
> @@ -41,8 +42,9 @@ static int ingenic_battery_get_property(struct 
> power_supply *psy,
>  			val->intval = POWER_SUPPLY_HEALTH_GOOD;
>  		return ret;
>  	case POWER_SUPPLY_PROP_VOLTAGE_NOW:
> -		ret = iio_read_channel_processed(bat->channel, &val->intval);
> -		val->intval *= 1000;
> +		ret = iio_read_channel_processed_scale(bat->channel,
> +						       &val->intval,
> +						       1000);
>  		return ret;
>  	case POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN:
>  		val->intval = info->voltage_min_design_uv;