Re: [PATCH v1 5/8] watchdog: f71808e_wdt: do stricter parameter validation

[Guenter Roeck <linux@roeck-us.net>]

On Thu, Jun 11, 2020 at 09:17:46PM +0200, Ahmad Fatoum wrote:
> We check the f71862fg_pin module parameter every time a watchdog device
> for the f71862fg is opened, but the parameter can't change at runtime.
> 
> If we move the check to the start of init:
> 
>   - We catch userspace passing invalid, but unused, values
>   - We check the condition only once
>   - We simplify the code
> 
> Do so.
> 
> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>

Reviewed-by: Guenter Roeck <linux@roeck-us.net>

> ---
>  drivers/watchdog/f71808e_wdt.c | 37 +++++++++++-----------------------
>  1 file changed, 12 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/watchdog/f71808e_wdt.c b/drivers/watchdog/f71808e_wdt.c
> index 26bf366aebc2..9f7823819ed1 100644
> --- a/drivers/watchdog/f71808e_wdt.c
> +++ b/drivers/watchdog/f71808e_wdt.c
> @@ -306,27 +306,6 @@ static int watchdog_keepalive(void)
>  	return err;
>  }
>  
> -static int f71862fg_pin_configure(unsigned short ioaddr)
> -{
> -	/* When ioaddr is non-zero the calling function has to take care of
> -	   mutex handling and superio preparation! */
> -
> -	if (f71862fg_pin == 63) {
> -		if (ioaddr) {
> -			/* SPI must be disabled first to use this pin! */
> -			superio_clear_bit(ioaddr, SIO_REG_ROM_ADDR_SEL, 6);
> -			superio_set_bit(ioaddr, SIO_REG_MFUNCT3, 4);
> -		}
> -	} else if (f71862fg_pin == 56) {
> -		if (ioaddr)
> -			superio_set_bit(ioaddr, SIO_REG_MFUNCT1, 1);
> -	} else {
> -		pr_err("Invalid argument f71862fg_pin=%d\n", f71862fg_pin);
> -		return -EINVAL;
> -	}
> -	return 0;
> -}
> -
>  static int watchdog_start(void)
>  {
>  	int err;
> @@ -352,9 +331,13 @@ static int watchdog_start(void)
>  		break;
>  
>  	case f71862fg:
> -		err = f71862fg_pin_configure(watchdog.sioaddr);
> -		if (err)
> -			goto exit_superio;
> +		if (f71862fg_pin == 63) {
> +			/* SPI must be disabled first to use this pin! */
> +			superio_clear_bit(watchdog.sioaddr, SIO_REG_ROM_ADDR_SEL, 6);
> +			superio_set_bit(watchdog.sioaddr, SIO_REG_MFUNCT3, 4);
> +		} else if (f71862fg_pin == 56) {
> +			superio_set_bit(watchdog.sioaddr, SIO_REG_MFUNCT1, 1);
> +		}
>  		break;
>  
>  	case f71868:
> @@ -810,7 +793,6 @@ static int __init f71808e_find(int sioaddr)
>  		break;
>  	case SIO_F71862_ID:
>  		watchdog.type = f71862fg;
> -		err = f71862fg_pin_configure(0); /* validate module parameter */
>  		break;
>  	case SIO_F71868_ID:
>  		watchdog.type = f71868;
> @@ -859,6 +841,11 @@ static int __init f71808e_init(void)
>  	int err = -ENODEV;
>  	int i;
>  
> +	if (f71862fg_pin != 63 && f71862fg_pin != 56) {
> +		pr_err("Invalid argument f71862fg_pin=%d\n", f71862fg_pin);
> +		return -EINVAL;
> +	}
> +
>  	for (i = 0; i < ARRAY_SIZE(addrs); i++) {
>  		err = f71808e_find(addrs[i]);
>  		if (err == 0)