linux-kernel - Re: [PATCH 1/7] platform/x86: fujitsu-laptop: do not use kfifo for storing hotkey scancodes

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Message-ID: <20170623001458.GE24368@marvin.atrad.com.au>
Date:   Fri, 23 Jun 2017 09:44:58 +0930
From:   Jonathan Woithe <jwoithe@...t42.net>
To:     Darren Hart <dvhart@...radead.org>
Cc:     Micha?? K??pie?? <kernel@...pniu.pl>,
        Rafael Wysocki <rjw@...ysocki.net>,
        Andy Shevchenko <andy@...radead.org>,
        platform-driver-x86@...r.kernel.org, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/7] platform/x86: fujitsu-laptop: do not use kfifo for
 storing hotkey scancodes

On Thu, Jun 22, 2017 at 04:58:09PM -0700, Darren Hart wrote:
> On Thu, Jun 22, 2017 at 10:46:19PM +0200, Micha?? K??pie?? wrote:
> > > The events seen by userspace with the original code would be "A-press",
> > > "B-press", "A-release", "B-release".  With the revised code the order of the
> > > release events would be reversed compared to the previous behaviour.  That
> > > is, unless I've misunderstood how sparse_keymap_report_event() works.
> > 
> > All you wrote above is correct and this patch does change the order of
> > release events sent to userspace when multiple hotkeys are pressed
> > simultaneously.  The question is: is it relevant for any practical
> > scenario?
> > 
> > Anyway, I find this matter to be of secondary importance.  The primary
> > objective of this patch is to get rid of the kfifo.  If anyone has
> > strong feelings about the change in event ordering, I will be happy to
> > revert to FIFO in v2.
> 
> This all looks reasonable to me, I don't see anything requiring a respin.

I agree it is of seconary importance.  To me, using LIFO release order is
counter-intuitive, but it's the sort of question that if put to 100 people
you'll get a 50/50 split of opinions.

Especially since the whole "multiple buttons held at once" scenario is
rather unusual we can go with switching the order if others don't see a
problem with the behavioural change.

Regards
  jonathan