Hi,
On 18 April 2013 14:14, Alexander Graf agraf@suse.de wrote:
Am 18.04.2013 um 09:32 schrieb Pranavkumar Sawargaonkar pranavkumar@linaro.org:
On 18 April 2013 12:21, Rusty Russell rusty@rustcorp.com.au wrote:
PranavkumarSawargaonkar pranavkumar@linaro.org writes:
From: Pranavkumar Sawargaonkar pranavkumar@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.
At the time of early printk we do not have virtio queues initialized so even if we use poll for ack than interrupt, without queues being set how that is possible ? Hence we have added simple config register which can be polled without setting up queues.
The advantage to that would be that no host changes are required whatsoever and the interface strictly stays as it is.
Alex
Thanks, Pranav