On Thu, Jul 19, 2018 at 9:19 PM, Giulio Benetti <giulio.benetti@xxxxxxxxxxxxxxxx> wrote: > Hi Andy, > > Il 18/07/2018 18:26, Andy Shevchenko ha scritto: >> >> On Wed, Jul 18, 2018 at 5:06 PM, Giulio Benetti >> <giulio.benetti@xxxxxxxxxxxxxxxx> wrote: >> >>>>> + int ret; >>>>> + >>>>> + ret = kstrtobool(buf, &freq_test_en); >>>>> + if (ret == -EINVAL) { >> >> >>>> What kind of other error code you may expect and why they are not >>>> considered as no error? >> >> >>> According to documentation, kstrtobool can only fail with -EINVAL. >>> See: >>> https://elixir.bootlin.com/linux/v4.18-rc5/source/lib/kstrtox.c#L332 >> >> >> That's correct. So, what do you want to show by explicitly mentioned >> an error code in the condition? >> > > So you mean I should check for negative values instead of specific error, > right? Learn from the existing code. As you found kstrtobool() returns either 0 (no error), or -EINVAL (the only possible error code for now). Checking ret for non-zero is enough. Thus, if (ret) { ... return ret; } should do a job. -- With Best Regards, Andy Shevchenko