linux-kernel - Re: [PATCH 2/5] serial: core: add sysfs attribute to suppress ready signalling on open

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Date:   Tue, 1 Dec 2020 17:44:10 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Johan Hovold <johan@...nel.org>
Cc:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Jiri Slaby <jirislaby@...nel.org>,
        "Mychaela N . Falconia" <falcon@...ecalypso.org>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        USB <linux-usb@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/5] serial: core: add sysfs attribute to suppress ready
 signalling on open

On Tue, Dec 01, 2020 at 12:05:23PM +0100, Johan Hovold wrote:
> On Tue, Dec 01, 2020 at 12:55:54PM +0200, Andy Shevchenko wrote:
> > On Tue, Dec 1, 2020 at 10:20 AM Johan Hovold <johan@...nel.org> wrote:
> > > On Mon, Nov 30, 2020 at 08:27:54PM +0200, Andy Shevchenko wrote:
> > > > On Mon, Nov 30, 2020 at 5:42 PM Johan Hovold <johan@...nel.org> wrote:
> > 
> > > > > +       ret = kstrtouint(buf, 0, &val);
> > > > > +       if (ret)
> > > > > +               return ret;
> > > >
> > > > > +       if (val > 1)
> > > > > +               return -EINVAL;
> > > >
> > > > Can't we utilise kstrtobool() instead?
> > >
> > > I chose not to as kstrtobool() results in a horrid interface. To many
> > > options to do the same thing and you end up with confusing things like
> > > "0x01" being accepted but treated as false (as only the first character
> > > is considered).
> > 
> > And this is perfectly fine. 0x01 is not boolean.
> 
> 0x01 is 1 and is generally treated as boolean true as you know.
> 
> So why should a sysfs-interface accept it as valid input and treat it as
> false? That's just bad design.

The "design" was to accept "sane" flags here:
	1, y, Y mean "enable"
	0, n, N mean "disable"

We never thought someone would try to write "0x01" as "enable" for a
boolean flag :)

So it's not a bad design, it works well what it was designed for.  It
just is NOT designed for hex values.

If your sysfs file is "enable/disable", then please, use kstrtobool, as
that is the standard way of doing this, and don't expect 0x01 to work :)

thanks,

greg k-h