Re: [PATCH v3 2/2] auxdisplay: charlcd: Deduplicate simple_strtoul()

Petr Mladek
2019-07-08T13:16:55Z

On Thu 2019-07-04 14:55:32, Andy Shevchenko wrote:
> Like in the commit
> 8b2303de399f ("serial: core: Fix handling of options after MMIO address")
> we may use simple_strtoul() which in comparison to kstrtoul() can do conversion
> in-place without additional and unnecessary code to be written.
>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
> - no change since v2
> drivers/auxdisplay/charlcd.c | 34 +++++++---------------------------
> 1 file changed, 7 insertions(+), 27 deletions(-)
>
> diff --git a/drivers/auxdisplay/charlcd.c b/drivers/auxdisplay/charlcd.c
> index 92745efefb54..3858dc7a4154 100644
> --- a/drivers/auxdisplay/charlcd.c
> +++ b/drivers/auxdisplay/charlcd.c
> @@ -287,31 +287,6 @@ static int charlcd_init_display(struct charlcd *lcd)
> return 0;
> }
>
> -/*
> - * Parses an unsigned integer from a string, until a non-digit character
> - * is found. The empty string is not accepted. No overflow checks are done.
> - *
> - * Returns whether the parsing was successful. Only in that case
> - * the output parameters are written to.
> - *
> - * TODO: If the kernel adds an inplace version of kstrtoul(), this function
> - * could be easily replaced by that.
> - */
> -static bool parse_n(const char *s, unsigned long *res, const char **next_s)
> -{
> - if (!isdigit(*s))
> - return false;
> -
> - *res = 0;
> - while (isdigit(*s)) {
> - *res = *res * 10 + (*s - '0');
> - ++s;
> - }
> -
> - *next_s = s;
> - return true;
> -}
> -
> /*
> * Parses a movement command of the form "(.*);", where the group can be
> * any number of subcommands of the form "(x|y)[0-9]+".
> @@ -336,6 +311,7 @@ static bool parse_xy(const char *s, unsigned long *x, unsigned long *y)
> {
> unsigned long new_x = *x;
> unsigned long new_y = *y;
> + char *p;
>
> for (;;) {
> if (!*s)
> @@ -345,11 +321,15 @@ static bool parse_xy(const char *s, unsigned long *x, unsigned long *y)
> break;
>
> if (*s == 'x') {
> - if (!parse_n(s + 1, &new_x, &s))
> + new_x = simple_strtoul(s + 1, &p, 10);

simple_strtoul() tries to detect the base even when it has been
explicitely specified. I am afraid that it might cause some
regressions.

For example, the following input is strange but it is valid:

x0x10; new code would return (16, <orig_y>) instead of (10, <orig_y>)
x010; new code would return (8, <orig_y>) instead of (10, <orig_y>)

Best Regards,
Petr