[RFC] arm64: Early printk support for virtio-mmio console devices.

[Alexander Graf]

Am 18.04.2013 um 09:32 schrieb Pranavkumar Sawargaonkar <pranavkumar at linaro.org>:

> On 18 April 2013 12:21, Rusty Russell <rusty at rustcorp.com.au> wrote:
>> 
>> PranavkumarSawargaonkar <pranavkumar at linaro.org> writes:
>>> From: Pranavkumar Sawargaonkar <pranavkumar at linaro.org>
>>> 
>>> This patch implements early printk support for virtio-mmio console devices without using any hypercalls.
>> 
>> This makes some sense, though not sure that early console *read* makes
>> much sense.  I can see the PCI version of this being useful as well.
> 
> Read can be useful for "mach-virt" which will have only virtio console
> as a console device. Then if someone wants to have UEFI or any other
> boot-loader emulation, which expects user to input few things, in that
> case read might become handy.

A boot loader should easily be able to implement virtio-console for real.

In fact, you should be able to do a simple virtio-console implementation for early printk too, that polls the host for acks rather than use interrupts. Check out my s390-zipl code for reference. I use that there.

The advantage to that would be that no host changes are required whatsoever and the interface strictly stays as it is.


Alex