linux-kernel - Re: [PATCH 0/2] Early printk support for virtio console devices.

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Message-ID: <87txmfo0rl.fsf@rustcorp.com.au>
Date:	Tue, 07 May 2013 14:16:22 +0930
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Peter Maydell <peter.maydell@...aro.org>
Cc:	Alexander Graf <agraf@...e.de>,
	Pranavkumar Sawargaonkar <pranavkumar@...aro.org>,
	"linux-arm-kernel\@lists.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linaro-kernel\@lists.linaro.org" <linaro-kernel@...ts.linaro.org>,
	"patches\@linaro.org" <patches@...aro.org>,
	"linux-kernel\@vger.kernel.org List" <linux-kernel@...r.kernel.org>,
	"kvmarm\@lists.cs.columbia.edu" <kvmarm@...ts.cs.columbia.edu>,
	Amit Shah <amit.shah@...hat.com>
Subject: Re: [PATCH 0/2] Early printk support for virtio console devices.

Peter Maydell <peter.maydell@...aro.org> writes:
> On 6 May 2013 06:11, Rusty Russell <rusty@...tcorp.com.au> wrote:
>> Peter Maydell <peter.maydell@...aro.org> writes:
>>> To be actually useful we need to also specify something in
>>> the device tree to say "here is where you will find your
>>> emergency output and what it is".
>>
>> Hmm, I'm not sure that's true.  It looks like it needs:
>>
>> 1) An enhancment to the vdev->set_config callback to pass through (at
>>    least) an offset, probably offset and length.
>>
>> 2) An emerg_write() function ptr which can be called at any time, set by
>>    virtio_console.c's class_init:
>
> That all looks like sensible QEMU implementation possibilities
> but it seems to be a bit of a non-sequitur from "how do we
> tell the kernel to actually use this?"

You enable the feature in the virtio console device, and a kernel
compiled with EARLY_PRINTK will use it?

Cheers,
Rusty.
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