linux-kernel - Fwd: [PATCH 2/3] usb: type-c: USB Type-C Connector System Software Interface

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Date:	Thu, 11 Feb 2016 10:13:11 +0200
From:	Andy Shevchenko <andy.shevchenko@...il.com>
To:	Oliver Neukum <oneukum@...e.de>
Cc:	Felipe Balbi <balbi@...nel.org>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Mathias Nyman <mathias.nyman@...ux.intel.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	USB <linux-usb@...r.kernel.org>
Subject: Fwd: [PATCH 2/3] usb: type-c: USB Type-C Connector System Software Interface

---------- Forwarded message ----------
From: Andy Shevchenko <andy.shevchenko@...il.com>
Date: Thu, Feb 11, 2016 at 10:10 AM
Subject: Re: [PATCH 2/3] usb: type-c: USB Type-C Connector System
Software Interface
To: Oliver Neukum <oneukum@...e.de>


On Wed, Feb 10, 2016 at 5:08 PM, Oliver Neukum <oneukum@...e.de> wrote:
> On Wed, 2016-02-10 at 16:24 +0200, Andy Shevchenko wrote:
>> On Wed, Feb 10, 2016 at 4:15 PM, Oliver Neukum <oneukum@...e.com> wrote:
>> > On Wed, 2016-02-10 at 13:56 +0200, Andy Shevchenko wrote:
>> >> > +err:
>> >> > +       if (i > 0)
>> >> > +               for (; i >= 0; i--, con--)
>> >> > +                       typec_unregister_port(con->port);
>> >>
>> >> Perhaps
>> >>
>> >> while (--i >= 0) {
>> >>  ...
>> >> }
>> >
>> > While we are at it. No we should not change the semantics
>> > of conditionals for the sake of appearance.
>>
>> I'm sorry I didn't get you.
>> How this more or less standard pattern to clean up stuff on error path
>> does with conditional semantics?
>
> You change a postdecrement to a predecrement. The highest
> number the loop is executed for is changed.

I still didn't get.
Variable i is just counter here,

And it seems there is a bug, since when i == 1, we will have

i = 1, con == connector[0]:
typec_unregister_port(con->port);

i = 0, con == connector[1]:
typec_unregister_port(con->port); <<< It wasn't registered yet!

The correct code should be something like
if (i > 0)
 for (--i; i >= 0; i--) {}

Which
a) makes conditional redundant;
b) classical pattern of while (--i >= 0) {}

So where am I wrong?

--
With Best Regards,
Andy Shevchenko


-- 
With Best Regards,
Andy Shevchenko