linux-kernel - Re: [PATCH 3/7] hwmon: (dell-smm) Make fan/temp sensor number a u8

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Date:   Tue, 15 Feb 2022 20:37:44 +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 3/7] hwmon: (dell-smm) Make fan/temp sensor number a u8

On Tuesday 15 February 2022 20:11:09 Armin Wolf wrote:
> Right now, we only use bits 0 to 7 of the fan/temp sensor number
> by doing number & 0xff. Passing the value as a u8 makes this
> step unnecessary. Also add checks to the ioctl handler since
> users might get confused when passing 0x00000101 does the same
> as passing 0x00000001.
> 
> 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 | 68 ++++++++++++++++++++++------------
>  1 file changed, 45 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/hwmon/dell-smm-hwmon.c b/drivers/hwmon/dell-smm-hwmon.c
> index 3b49e55d060f..a102034a1d38 100644
> --- a/drivers/hwmon/dell-smm-hwmon.c
> +++ b/drivers/hwmon/dell-smm-hwmon.c
> @@ -21,6 +21,7 @@
>  #include <linux/errno.h>
>  #include <linux/hwmon.h>
>  #include <linux/init.h>
> +#include <linux/kernel.h>
>  #include <linux/module.h>
>  #include <linux/mutex.h>
>  #include <linux/platform_device.h>
> @@ -254,46 +255,52 @@ static int i8k_smm(struct smm_regs *regs)
>  /*
>   * Read the fan status.
>   */
> -static int i8k_get_fan_status(const struct dell_smm_data *data, int fan)
> +static int i8k_get_fan_status(const struct dell_smm_data *data, u8 fan)
>  {
> -	struct smm_regs regs = { .eax = I8K_SMM_GET_FAN, };
> +	struct smm_regs regs = {
> +		.eax = I8K_SMM_GET_FAN,
> +		.ebx = fan,
> +	};
> 
>  	if (data->disallow_fan_support)
>  		return -EINVAL;
> 
> -	regs.ebx = fan & 0xff;
>  	return i8k_smm(&regs) ? : regs.eax & 0xff;
>  }
> 
>  /*
>   * Read the fan speed in RPM.
>   */
> -static int i8k_get_fan_speed(const struct dell_smm_data *data, int fan)
> +static int i8k_get_fan_speed(const struct dell_smm_data *data, u8 fan)
>  {
> -	struct smm_regs regs = { .eax = I8K_SMM_GET_SPEED, };
> +	struct smm_regs regs = {
> +		.eax = I8K_SMM_GET_SPEED,
> +		.ebx = fan,
> +	};
> 
>  	if (data->disallow_fan_support)
>  		return -EINVAL;
> 
> -	regs.ebx = fan & 0xff;
>  	return i8k_smm(&regs) ? : (regs.eax & 0xffff) * data->i8k_fan_mult;
>  }
> 
>  /*
>   * Read the fan type.
>   */
> -static int _i8k_get_fan_type(const struct dell_smm_data *data, int fan)
> +static int _i8k_get_fan_type(const struct dell_smm_data *data, u8 fan)
>  {
> -	struct smm_regs regs = { .eax = I8K_SMM_GET_FAN_TYPE, };
> +	struct smm_regs regs = {
> +		.eax = I8K_SMM_GET_FAN_TYPE,
> +		.ebx = fan,
> +	};
> 
>  	if (data->disallow_fan_support || data->disallow_fan_type_call)
>  		return -EINVAL;
> 
> -	regs.ebx = fan & 0xff;
>  	return i8k_smm(&regs) ? : regs.eax & 0xff;
>  }
> 
> -static int i8k_get_fan_type(struct dell_smm_data *data, int fan)
> +static int i8k_get_fan_type(struct dell_smm_data *data, u8 fan)
>  {
>  	/* I8K_SMM_GET_FAN_TYPE SMM call is expensive, so cache values */
>  	if (data->fan_type[fan] == INT_MIN)
> @@ -305,14 +312,16 @@ static int i8k_get_fan_type(struct dell_smm_data *data, int fan)
>  /*
>   * Read the fan nominal rpm for specific fan speed.
>   */
> -static int __init i8k_get_fan_nominal_speed(const struct dell_smm_data *data, int fan, int speed)
> +static int __init i8k_get_fan_nominal_speed(const struct dell_smm_data *data, u8 fan, int speed)
>  {
> -	struct smm_regs regs = { .eax = I8K_SMM_GET_NOM_SPEED, };
> +	struct smm_regs regs = {
> +		.eax = I8K_SMM_GET_NOM_SPEED,
> +		.ebx = fan | (speed << 8),
> +	};
> 
>  	if (data->disallow_fan_support)
>  		return -EINVAL;
> 
> -	regs.ebx = (fan & 0xff) | (speed << 8);
>  	return i8k_smm(&regs) ? : (regs.eax & 0xffff) * data->i8k_fan_mult;
>  }
> 
> @@ -333,7 +342,7 @@ static int i8k_enable_fan_auto_mode(const struct dell_smm_data *data, bool enabl
>  /*
>   * Set the fan speed (off, low, high, ...).
>   */
> -static int i8k_set_fan(const struct dell_smm_data *data, int fan, int speed)
> +static int i8k_set_fan(const struct dell_smm_data *data, u8 fan, int speed)
>  {
>  	struct smm_regs regs = { .eax = I8K_SMM_SET_FAN, };
> 
> @@ -341,33 +350,35 @@ static int i8k_set_fan(const struct dell_smm_data *data, int fan, int speed)
>  		return -EINVAL;
> 
>  	speed = (speed < 0) ? 0 : ((speed > data->i8k_fan_max) ? data->i8k_fan_max : speed);
> -	regs.ebx = (fan & 0xff) | (speed << 8);
> +	regs.ebx = fan | (speed << 8);
> 
>  	return i8k_smm(&regs);
>  }
> 
> -static int __init i8k_get_temp_type(int sensor)
> +static int __init i8k_get_temp_type(u8 sensor)
>  {
> -	struct smm_regs regs = { .eax = I8K_SMM_GET_TEMP_TYPE, };
> +	struct smm_regs regs = {
> +		.eax = I8K_SMM_GET_TEMP_TYPE,
> +		.ebx = sensor,
> +	};
> 
> -	regs.ebx = sensor & 0xff;
>  	return i8k_smm(&regs) ? : regs.eax & 0xff;
>  }
> 
>  /*
>   * Read the cpu temperature.
>   */
> -static int _i8k_get_temp(int sensor)
> +static int _i8k_get_temp(u8 sensor)
>  {
>  	struct smm_regs regs = {
>  		.eax = I8K_SMM_GET_TEMP,
> -		.ebx = sensor & 0xff,
> +		.ebx = sensor,
>  	};
> 
>  	return i8k_smm(&regs) ? : regs.eax & 0xff;
>  }
> 
> -static int i8k_get_temp(int sensor)
> +static int i8k_get_temp(u8 sensor)
>  {
>  	int temp = _i8k_get_temp(sensor);
> 
> @@ -500,6 +511,9 @@ static long i8k_ioctl(struct file *fp, unsigned int cmd, unsigned long arg)
>  		if (copy_from_user(&val, argp, sizeof(int)))
>  			return -EFAULT;
> 
> +		if (val > U8_MAX || val < 0)
> +			return -EINVAL;
> +
>  		val = i8k_get_fan_speed(data, val);
>  		break;
> 
> @@ -507,6 +521,9 @@ static long i8k_ioctl(struct file *fp, unsigned int cmd, unsigned long arg)
>  		if (copy_from_user(&val, argp, sizeof(int)))
>  			return -EFAULT;
> 
> +		if (val > U8_MAX || val < 0)
> +			return -EINVAL;
> +
>  		val = i8k_get_fan_status(data, val);
>  		break;
> 
> @@ -517,6 +534,9 @@ static long i8k_ioctl(struct file *fp, unsigned int cmd, unsigned long arg)
>  		if (copy_from_user(&val, argp, sizeof(int)))
>  			return -EFAULT;
> 
> +		if (val > U8_MAX || val < 0)
> +			return -EINVAL;
> +
>  		if (copy_from_user(&speed, argp + 1, sizeof(int)))
>  			return -EFAULT;
> 
> @@ -924,7 +944,8 @@ static int __init dell_smm_init_hwmon(struct device *dev)
>  {
>  	struct dell_smm_data *data = dev_get_drvdata(dev);
>  	struct device *dell_smm_hwmon_dev;
> -	int i, state, err;
> +	int state, err;
> +	u8 i;
> 
>  	for (i = 0; i < DELL_SMM_NO_TEMP; i++) {
>  		data->temp_type[i] = i8k_get_temp_type(i);
> @@ -1245,7 +1266,8 @@ static int __init dell_smm_probe(struct platform_device *pdev)
>  {
>  	struct dell_smm_data *data;
>  	const struct dmi_system_id *id, *fan_control;
> -	int fan, ret;
> +	int ret;
> +	u8 fan;
> 
>  	data = devm_kzalloc(&pdev->dev, sizeof(struct dell_smm_data), GFP_KERNEL);
>  	if (!data)
> --
> 2.30.2
>