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Date: Fri, 28 Jun 2013 15:43:17 +0400
From: Michael Tokarev <mjt@tls.msk.ru>
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Subject: Re: [Qemu-devel] [PATCH] display: stop using DT_NOGRAPHIC,
	use DT_NONE
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>, Anthony Liguori <aliguori@us.ibm.com>, "Todd T. Fries" <todd@fries.net>, qemu-devel@nongnu.org

28.06.2013 15:34, Peter Maydell wrote:
> On 28 June 2013 12:29, Michael Tokarev <mjt@tls.msk.ru> wrote:
>> 28.06.2013 15:24, Peter Maydell wrote:
>>> ...in particular I don't think "-display none" should
>>> mean "don't allow ctrl-c" (though -nographic should
>>> continue to have that effect), and this patch currently
>>> introduces that behaviour change.
>>
>> As Anthony said before, -nographic is legacy.  So there should
>> be some more modern way to control this.  That's exactly the
>> change which I don't like myself.  But "don't allow ctrl-c"
>> which is currently bound to -nographic is equally wrong.
> 
> All I'm saying is that I use -display none and I like that
> it defaults to "ctrl-c works and kills qemu" and I don't
> want you to break that :-)

I'm not.  Code in qemu-char.c:

static bool stdio_allow_signal;

static void qemu_chr_set_echo_stdio(CharDriverState *chr, bool echo)
{
    ...
    /* if graphical mode, we allow Ctrl-C handling */
    if (!stdio_allow_signal)
        tty.c_lflag &= ~ISIG;
    ...
}

static CharDriverState *qemu_chr_open_stdio(ChardevStdio *opts)
{
    ...
    stdio_allow_signal = display_type != DT_NOGRAPHIC;
    if (opts->has_signal) {
        stdio_allow_signal = opts->signal;
    }
    ...
}


Note it is used only for stdio char device, like -serial stdio,
so if you _just_ use -display none, without -serial stdio, you
wont notice a change.

And note that original intention isn't exactly clear, either.
How it is related with, say, curses display which needs raw
keypresses?

Adding Paolo who wrote that code in bb002513.

Thanks,

/mjt