[PATCH v2 3/3] xen/arm: allow console=hvc0 to be omitted for guests

[Stefano Stabellini]

On Fri, 27 Feb 2015, Ian Campbell wrote:
> On Thu, 2015-02-26 at 18:22 +0000, Stefano Stabellini wrote:
> > On Wed, 18 Feb 2015, Ian Campbell wrote:
> > > On Wed, 2015-02-18 at 09:50 -0600, Rob Herring wrote:
> > > > On Wed, Feb 18, 2015 at 7:51 AM, Julien Grall <julien.grall at linaro.org> wrote:
> > > > > From: Ard Biesheuvel <ard.biesheuvel at linaro.org>
> > > > >
> > > > > This patch registers hvc0 as the preferred console if no console
> > > > > has been specified explicitly on the kernel command line.
> > > > >
> > > > > The purpose is to allow platform agnostic kernels and boot images
> > > > > (such as distro installers) to boot in a Xen/ARM domU without the
> > > > > need to modify the command line by hand.
> > > > 
> > > > How does this interact with DT chosen stdout-path?
> > > 
> > > I think it shouldn't any more than the existing calls from e.g. the 8250
> > > driver to preferred_console do.
> > >
> > > > Is there a node for hvc0?
> > > 
> > > Not a direct one, it is inferred from the presence of the general Xen
> > > node.
> > 
> > Xen PV consoles, including hvc0, as all the other Xen PV devices are
> > advertised on xenstore.
> 
> Do we actually use the xenstore node for hvc0? I thought we got it from
> hvmparams (so the primary it can be used before xenstore is up)

We always assume that at least one PV console is available and the first
one is a bit special because it can be setup before the xenstore driver
for early boot messages and debugging purposes. However even the first
console is advertised on xenstore.