linux-kernel - Re: [PATCH v2] hwmon: (asus_wmi_sensors) Save a few bytes of memory

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Date:   Sat, 2 Jul 2022 12:13:16 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc:     Ed Brindley <kernel@...davale.org>,
        Denis Pauk <pauk.denis@...il.com>,
        Jean Delvare <jdelvare@...e.com>, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org, linux-hwmon@...r.kernel.org
Subject: Re: [PATCH v2] hwmon: (asus_wmi_sensors) Save a few bytes of memory

On Sat, Jul 02, 2022 at 08:05:54AM +0200, Christophe JAILLET wrote:
> The first 'for' loop of asus_wmi_configure_sensor_setup() only computes
> the number and type of sensors that exist in the system.
> 
> Here, the 'temp_sensor' structure is only used to store the data collected
> by asus_wmi_sensor_info(). There is no point in using a devm_ variant for
> this allocation. This wastes some memory for no good reason.
> 
> Use the stack instead.
> 
> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>

Applied to hwmon-next.

Thanks,
Guenter

> ---
> v1 -> v2: Use the stack instead of kmalloc/kfree to simplify even more the
>           code (Guenter Roeck)
> ---
>  drivers/hwmon/asus_wmi_sensors.c | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/hwmon/asus_wmi_sensors.c b/drivers/hwmon/asus_wmi_sensors.c
> index 9e935e34c998..6e8a908171f0 100644
> --- a/drivers/hwmon/asus_wmi_sensors.c
> +++ b/drivers/hwmon/asus_wmi_sensors.c
> @@ -514,22 +514,20 @@ static int asus_wmi_configure_sensor_setup(struct device *dev,
>  	int i, idx;
>  	int err;
>  
> -	temp_sensor = devm_kcalloc(dev, 1, sizeof(*temp_sensor), GFP_KERNEL);
> -	if (!temp_sensor)
> -		return -ENOMEM;
> -
>  	for (i = 0; i < sensor_data->wmi.sensor_count; i++) {
> -		err = asus_wmi_sensor_info(i, temp_sensor);
> +		struct asus_wmi_sensor_info sensor;
> +
> +		err = asus_wmi_sensor_info(i, &sensor);
>  		if (err)
>  			return err;
>  
> -		switch (temp_sensor->data_type) {
> +		switch (sensor.data_type) {
>  		case TEMPERATURE_C:
>  		case VOLTAGE:
>  		case CURRENT:
>  		case FAN_RPM:
>  		case WATER_FLOW:
> -			type = asus_data_types[temp_sensor->data_type];
> +			type = asus_data_types[sensor.data_type];
>  			if (!nr_count[type])
>  				nr_types++;
>  			nr_count[type]++;