From: Arnd Bergmann <arnd@arndb.de>
To: linaro-kernel@lists.linaro.org
Cc: Anup Patel <anup.patel@linaro.org>,
        Peter Maydell <peter.maydell@linaro.org>, patches@linaro.org,
        "linux-kernel@vger.kernel.org List" <linux-kernel@vger.kernel.org>,
        Alexander Graf <agraf@suse.de>, kvmarm@lists.cs.columbia.edu,
        linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 0/2] Early printk support for virtio console devices.
Date: Fri, 26 Apr 2013 14:33:59 +0200
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On Friday 26 April 2013 17:36:16 Anup Patel wrote:
> On 26 April 2013 17:03, Peter Maydell <peter.maydell@linaro.org> wrote:
> > On 26 April 2013 12:19, Alexander Graf <agraf@suse.de> wrote:
> >> MMIO registers are handled by a different layer than the virtio
> >> console itself. After the virtio refactoring in QEMU, they will
> >> be completely separate drivers.
> >
> > Good point -- we don't really want to be mixing up the
> > transport and the backend. You can see it in the kvmtool
> > patch, in fact -- it introduces an "if this is virtio-console"
> > special case into the mmio.c file which previously was
> > entirely backend agnostic.
> 
> Well, we can always have virtio device specific config registers
> handle by virtio device backends and generic virtio config register
> handled by transport.
> 
> kvmtool patch is hacky because it does not provide virtio device
> specific config read/write callbacks.

Couldn't kvmtool implement the interface used by smh_printch()
for early output instead?

Or if that's not a fitting inteface, maybe a psci call for writing
a character to the console?

	Arnd
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