linux-kernel - Re: [PATCH v2 2/2] hwmon: (dell-smm) Unify i8k_ioctl() and i8k_ioctl

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Date:   Sat, 11 Dec 2021 17:05:51 +0100
From:   Pali Rohár <pali@...nel.org>
To:     Armin Wolf <W_Armin@....de>
Cc:     jdelvare@...e.com, linux@...ck-us.net, linux-hwmon@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] hwmon: (dell-smm) Unify i8k_ioctl() and
 i8k_ioctl_unlocked()

On Saturday 11 December 2021 16:54:22 Armin Wolf wrote:
> The only purpose of i8k_ioctl() is to call i8k_ioctl_unlocked()
> with i8k_mutex held. Judging from the hwmon code, this mutex
> only needs to be held when setting the fan speed/mode, so
> the operation of I8K_SET_FAN is guaranteed to be atomic.
> Unify both functions and reduce the locking of i8k_mutex
> to I8K_SET_FAN.
> 
> Tested on a Dell Inspiron 3505.
> 
> Signed-off-by: Armin Wolf <W_Armin@....de>

Reviewed-by: Pali Rohár <pali@...nel.org>

> ---
>  drivers/hwmon/dell-smm-hwmon.c | 28 +++++++++-------------------
>  1 file changed, 9 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/hwmon/dell-smm-hwmon.c b/drivers/hwmon/dell-smm-hwmon.c
> index 186d40938036..d8c6e75bb374 100644
> --- a/drivers/hwmon/dell-smm-hwmon.c
> +++ b/drivers/hwmon/dell-smm-hwmon.c
> @@ -449,12 +449,12 @@ static int i8k_get_power_status(void)
>   * Procfs interface
>   */
> 
> -static int
> -i8k_ioctl_unlocked(struct file *fp, struct dell_smm_data *data, unsigned int cmd, unsigned long arg)
> +static long i8k_ioctl(struct file *fp, unsigned int cmd, unsigned long arg)
>  {
> -	int val = 0;
> -	int speed, err;
> +	struct dell_smm_data *data = PDE_DATA(file_inode(fp));
>  	int __user *argp = (int __user *)arg;
> +	int speed, err;
> +	int val = 0;
> 
>  	if (!argp)
>  		return -EINVAL;
> @@ -516,11 +516,13 @@ i8k_ioctl_unlocked(struct file *fp, struct dell_smm_data *data, unsigned int cmd
>  		if (copy_from_user(&speed, argp + 1, sizeof(int)))
>  			return -EFAULT;
> 
> +		mutex_lock(&data->i8k_mutex);
>  		err = i8k_set_fan(data, val, speed);
>  		if (err < 0)
> -			return err;
> -
> -		val = i8k_get_fan_status(data, val);
> +			val = err;
> +		else
> +			val = i8k_get_fan_status(data, val);
> +		mutex_unlock(&data->i8k_mutex);
>  		break;
> 
>  	default:
> @@ -536,18 +538,6 @@ i8k_ioctl_unlocked(struct file *fp, struct dell_smm_data *data, unsigned int cmd
>  	return 0;
>  }
> 
> -static long i8k_ioctl(struct file *fp, unsigned int cmd, unsigned long arg)
> -{
> -	struct dell_smm_data *data = PDE_DATA(file_inode(fp));
> -	long ret;
> -
> -	mutex_lock(&data->i8k_mutex);
> -	ret = i8k_ioctl_unlocked(fp, data, cmd, arg);
> -	mutex_unlock(&data->i8k_mutex);
> -
> -	return ret;
> -}
> -
>  /*
>   * Print the information for /proc/i8k.
>   */
> --
> 2.30.2
>