Re: [PATCH v2 1/4] PCI/sysfs: Move to kstrtobool() to handle user input

[Bjorn Helgaas <helgaas@kernel.org>]

On Tue, Jul 06, 2021 at 01:06:19AM +0000, Krzysztof Wilczyński wrote:
> A common use case for many PCI sysfs objects is to either enable some
> functionality or trigger an action following a write to a given
> attribute where the value is written would be simply either "1" or "0"
> synonymous with either disabling or enabling something.
> 
> Parsing and validation of the input values are currently done using the
> kstrtoul() function to convert anything in the string buffer into an
> integer value - anything non-zero would be accepted as "enable" and zero
> simply as "disable".
> 
> For a while now, the kernel offers another function called kstrtobool()
> which was created to parse common user inputs into a boolean value, so
> that a range of values such as "y", "n", "1", "0", "on" and "off"
> handled in a case-insensitive manner would yield a boolean true or false
> result accordingly after the input string has been parsed.
> 
> Thus, move to kstrtobool() over kstrtoul() as it's a better fit for
> parsing user input, and it also implicitly offers a range check as only
> a finite amount of possible input values will be considered as valid.

If I understand correctly, a user could enable things by writing "5"
today, and if we switch to kstrbool(), that will no longer work.

I'm sure everything is *documented* such that one should write "1" or
other sensible values.  But I'm not sure there's benefit in adding new
restrictions.

Bjorn