On Tue, Apr 26, 2022 at 11:39:57AM +0200, Petr Mladek wrote:
> On Tue 2022-04-26 12:10:01, Jagdish Gediya wrote:
> > At many places in kernel, It is necessary to convert sysfs input
> > to corrosponding bool value e.g. "false" or "0" need to be converted
> > to bool false, "true" or "1" need to be converted to bool true,
> > places where such conversion is needed currently check the input
> > string manually, kstrtobool can be utilized at such places but
> > currently kstrtobool doesn't have support to "false"/"true".
> >
> > Add "false"/"true" support to kstrtobool while string conversion
> > to bool. Modify existing manual sysfs conversions to use kstrtobool().
>
> It looks reasonable. I would just do it slightly other way, see
> below.
>
> > This patch doesn't have any functionality change.
>
> This is not true. All kstrtobool() callers will react differently
> on the "true"/"false" input.
how? Is it related to performance as more characters are compared?
otherwise semantic wise they will get the expected response, correct?
> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> > Cc: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> > Cc: Richard Fitzgerald <rf@xxxxxxxxxxxxxxxxxxxxx>
> > Cc: Petr Mladek <pmladek@xxxxxxxx>
> > Signed-off-by: Jagdish Gediya <jvgediya@xxxxxxxxxxxxx>
> > ---
> > change in v2:
> > Modified kstrtobool to handle "false"/"true". Removed
> > new function sysfs_strbool introduced in v1.
> >
> > lib/kstrtox.c | 7 +++++++
> > mm/migrate.c | 6 +-----
> > mm/swap_state.c | 6 +-----
> > 3 files changed, 9 insertions(+), 10 deletions(-)
> >
> > diff --git a/lib/kstrtox.c b/lib/kstrtox.c
> > index 886510d248e5..3a5e29557838 100644
> > --- a/lib/kstrtox.c
> > +++ b/lib/kstrtox.c
> > @@ -377,6 +377,13 @@ int kstrtobool(const char *s, bool *res)
> > }
> > break;
> > default:
> > + if (!strncmp(s, "true", 4)) {
> > + *res = true;
> > + return 0;
> > + } else if (!strncmp(s, "false", 5)) {
> > + *res = false;
> > + return 0;
>
> It should be enough to check the first letter like we do in
> the other cases. I mean to set true when s[0] is 'T' or 't'
> and false when s[0] is 'F' or 'f'.
For "on" and "off", 2 characters are matched, so is it good enough
to compare only single character for strings "true" and "false"?
> Also please update comment above the function definition.
>
>
> > + }
> > break;
> > }
> >
>
> Best Regards,
> Petr
>
