Re: [PATCH 08/12] printk: Replace strncmp with str_has_prefix

[Joe Perches]

On Mon, 2019-07-29 at 23:15 +0800, Chuhong Yuan wrote:
> strncmp(str, const, len) is error-prone.
> We had better use newly introduced
> str_has_prefix() instead of it.
[]
> diff --git a/kernel/printk/braille.c b/kernel/printk/braille.c
[]
> @@ -11,10 +11,10 @@
>  
>  int _braille_console_setup(char **str, char **brl_options)
>  {
> -     if (!strncmp(*str, "brl,", 4)) {
> +     if (str_has_prefix(*str, "brl,")) {
>               *brl_options = "";
>               *str += 4;
> -     } else if (!strncmp(*str, "brl=", 4)) {
> +     } else if (str_has_prefix(*str, "brl=")) {
>               *brl_options = *str + 4;

Better to get rid of the += 4 uses too by storing the result
of str_has_prefix and using that as the addend.

Perhaps
        size_t len;

        if ((len = str_has_prefix(*str, "brl,"))) {
                *brl_options = "";
                *str += len;
        } else if ((len = str_has_prefix(*str, "brl="))) {
                etc...

>               *str = strchr(*brl_options, ',');
>               if (!*str) {
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
[]
> @@ -121,13 +121,13 @@ static int __control_devkmsg(char *str)
>       if (!str)
>               return -EINVAL;
>  
> -     if (!strncmp(str, "on", 2)) {
> +     if (str_has_prefix(str, "on")) {
>               devkmsg_log = DEVKMSG_LOG_MASK_ON;
>               return 2;
> -     } else if (!strncmp(str, "off", 3)) {
> +     } else if (str_has_prefix(str, "off")) {
>               devkmsg_log = DEVKMSG_LOG_MASK_OFF;
>               return 3;
> -     } else if (!strncmp(str, "ratelimit", 9)) {
> +     } else if (str_has_prefix(str, "ratelimit")) {
>               devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT;
>               return 9;
>       }

here too.