linux-kernel - Re: [PATCH v3 2/2] hwmon: Support set

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Date:   Mon, 21 Jun 2021 13:30:44 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     Zhang Rui <rui.zhang@...el.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Amit Kucheria <amitk@...nel.org>,
        Jean Delvare <jdelvare@...e.com>, linux-hwmon@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-tegra@...r.kernel.org
Subject: Re: [PATCH v3 2/2] hwmon: Support set_trips() of thermal device ops

On Mon, Jun 21, 2021 at 09:40:58PM +0300, Dmitry Osipenko wrote:
> Support set_trips() callback of thermal device ops. This allows HWMON
> device to operatively notify thermal core about temperature changes, which
> is very handy to have in a case where HWMON sensor is used by CPU thermal
> zone that performs passive cooling and emergency shutdown on overheat.
> Thermal core will be able to react faster to temperature changes.
> 

I think that warrants an explanation why it doesn't matter if the
code doesn't really set any trip points.

> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> ---
>  drivers/hwmon/hwmon.c | 32 ++++++++++++++++++++++++++++++++
>  1 file changed, 32 insertions(+)
> 
> diff --git a/drivers/hwmon/hwmon.c b/drivers/hwmon/hwmon.c
> index fd47ab4e6892..e74dc81e650d 100644
> --- a/drivers/hwmon/hwmon.c
> +++ b/drivers/hwmon/hwmon.c
> @@ -153,8 +153,40 @@ static int hwmon_thermal_get_temp(void *data, int *temp)
>  	return 0;
>  }
>  
> +static int hwmon_thermal_set_trips(void *data, int low, int high)
> +{
> +	struct hwmon_thermal_data *tdata = data;
> +	struct hwmon_device *hwdev = to_hwmon_device(tdata->dev);
> +	const struct hwmon_chip_info *chip = hwdev->chip;
> +	const struct hwmon_channel_info **info = chip->info;
> +	unsigned int i;
> +
> +	if (!chip->ops->write)
> +		return 0;
> +
> +	for (i = 1; info[i] && info[i]->type != hwmon_temp; i++)
> +		continue;

Why start with index 1 ? While index 0 is commonly used for chip data,
that is not mandatory.

> +
> +	if (info[i] && info[i]->config[tdata->index] & HWMON_T_MIN) {
> +		int err = chip->ops->write(tdata->dev, hwmon_temp,
> +					   hwmon_temp_min, tdata->index, low);

checkpatch will complain here because it expects an empty line after a
declaration. Since err is used in multiple conditionals, I would suggest
to declare it once in the function header.

> +		if (err < 0 && err != -EOPNOTSUPP)

"< 0" is unnecessary.

> +			return err;
> +	}
> +
> +	if (info[i] && info[i]->config[tdata->index] & HWMON_T_MAX) {
> +		int err = chip->ops->write(tdata->dev, hwmon_temp,
> +					   hwmon_temp_max, tdata->index, high);
> +		if (err < 0 && err != -EOPNOTSUPP)

"< 0" is unnecessary.

> +			return err;
> +	}
> +
> +	return 0;
> +}
> +
>  static const struct thermal_zone_of_device_ops hwmon_thermal_ops = {
>  	.get_temp = hwmon_thermal_get_temp,
> +	.set_trips = hwmon_thermal_set_trips,
>  };
>  
>  static void hwmon_thermal_remove_sensor(void *data)