linux-kernel - Re: [RFC] tty/sysrq: Add alternative SysRq key

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Date:   Fri, 5 Nov 2021 14:27:17 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Andrzej Pietrasiewicz <andrzej.p@...labora.com>
Cc:     "Maciej W. Rozycki" <macro@...am.me.uk>,
        Pavel Machek <pavel@....cz>, linux-kernel@...r.kernel.org,
        linux-input@...r.kernel.org,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Jiri Slaby <jirislaby@...nel.org>, kernel@...labora.com
Subject: Re: [RFC] tty/sysrq: Add alternative SysRq key

On Fri, Nov 05, 2021 at 02:01:23PM +0100, Andrzej Pietrasiewicz wrote:
> Hi,
> 
> W dniu 04.11.2021 o 15:17, Andrzej Pietrasiewicz pisze:
> > Hi Maciej,
> > 
> > W dniu 04.11.2021 o 14:13, Maciej W. Rozycki pisze:
> > > On Thu, 4 Nov 2021, Maciej W. Rozycki wrote:
> > > 
> > > >   The reason for this is with their more recent laptops Lenovo in their
> > > > infinite wisdom have placed the <PrintScreen> key (which in a traditional
> > > > PS/2-keyboard manner produces <SysRq> when combined with <Alt>) in their
> > > > keyboards between the right <Alt> and <Ctrl> keys.  With thumbs not being
> > > > as accurate as other fingers (and the overall misdesign of the keyboard
> > > > and touchpad interface) you can imagine how often I have inadvertently hit
> > > > <SysRq> combined with a letter key, wreaking havoc to my system (and of
> > > > course I want to keep the key enabled for times when I do need it).
> > > 
> > >   On second thoughts this can be disabled with `setkeycodes 54 0' once we
> > > do have an alternative combination available.
> > > 
> > 
> > Doesn't `setkeycodes` affect only one keyboard? What if there are more
> > keyboards connected to a machine?
> > 
> >  From drivers/tty/vt/keyboard.c:
> > 
> > /*
> >   * Translation of scancodes to keycodes. We set them on only the first
> >   * keyboard in the list that accepts the scancode and keycode.
> >   * Explanation for not choosing the first attached keyboard anymore:
> >   *  USB keyboards for example have two event devices: one for all "normal"
> >   *  keys and one for extra function keys (like "volume up", "make coffee",
> >   *  etc.). So this means that scancodes for the extra function keys won't
> >   *  be valid for the first event device, but will be for the second.
> >   */
> > 
> 
> My second thoughts: if we run `setkeycodes` to map, say, F10 as SysRq,
> don't we lose F10?

The fact that this patch adds a "new" sysrq key no matter what is a
non-starter, please think through the consequences of such a change...

So no, as-is, this change is not acceptable at all, and I would be
amazed if anyone would ship such a thing.

thanks,

greg k-h