linux-kernel - Re: [PATCH 1/2] lib: Add early cpio decoder

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Message-ID: <50463399.70506@zytor.com>
Date:	Tue, 04 Sep 2012 10:00:09 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Thomas Renninger <trenn@...e.de>
CC:	linux-kernel@...r.kernel.org, lenb@...nel.org,
	robert.moore@...el.com, Fenghua Yu <fenghua.yu@...el.com>,
	initramfs@...r.kernel.org, bigeasy@...utronix.de, vojcek@...n.pl,
	eric.piel@...mplin-utc.net, linux-acpi@...r.kernel.org,
	yinghai@...nel.org, "H. Peter Anvin" <hpa@...ux.intel.com>
Subject: Re: [PATCH 1/2] lib: Add early cpio decoder

On 08/30/2012 02:29 AM, Thomas Renninger wrote:
> From: "H. Peter Anvin" <hpa@...ux.intel.com>
>
> Add a simple cpio decoder without library dependencies for the purpose
> of extracting components from the initramfs blob for early kernel
> uses.  Intended consumers so far are microcode and ACPI override.
>
> Signed-off-by: H. Peter Anvin <hpa@...ux.intel.com>
> CC: Thomas Renninger <trenn@...e.de>
> Link: http://lkml.kernel.org/r/201203261651.29640.trenn@suse.de
> Signed-off-by: Thomas Renninger <trenn@...e.de>

I was trying to figure out if there is a way to do what you want 
(support for multiple files) without the problems of the callback 
interface.  I think it is actually fairly straightforward; we need a 
prefix iterator (so you can give it a string like "kernel/acpi/" rather 
than a full filename) and it needs to be able to accept a "last" pointer 
so it can resume scanning at the point it last left off.  That should be 
a pretty trivial change.

The other thing we presumably want to do -- and this is generic -- is to 
be able to handle multiple sources for the initramfs; at the very least 
there is built in vs provided from the boot loader.  I had originally 
intended to just handle that by calling the earlycpio function once per 
block, but the "last left off" bit makes that a little harder.  Need to 
think about that a little bit.

I am guessing that this may not need to be something we need from the 
very beginning, or am I wrong?

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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