[PATCH 0/2] Early printk support for virtio console devices.

From: Pranavkumar Sawargaonkar
Date: Fri Apr 26 2013 - 07:06:19 EST

This patch-set implements early printk support for virtio console devices without using any hypercalls.

The current virtio early printk code in kernel expects that hypervisor will provide some mechanism generally a hypercall to support early printk. This patch-set does not break existing hypercall based early print support.

This implementation adds:
1. Early writeonly register named early_wr in virtio console's config space.
2. Host feature flags namely VIRTIO_CONSOLE_F_EARLY_WRITE for telling guest about early-write capability in console device.

Early write mechanism:
1. When a guest wants to out some character, it has to simply write the character to early_wr register in config space of virtio console device.

Pranavkumar Sawargaonkar (2):
virtio: console: Add early writeonly register to config space
arm64: earlyprintk support for virtio-mmio console

Documentation/virtual/virtio-spec.txt | 13 ++++++++++--
arch/arm64/kernel/early_printk.c | 35 +++++++++++++++++++++++++++++++++
include/uapi/linux/virtio_console.h | 3 +++
3 files changed, 49 insertions(+), 2 deletions(-)


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