Date: Thu, 7 Jun 2007 20:38:44 +0100
From: Christoph Hellwig <hch@infradead.org>
To: carsteno@de.ibm.com
Cc: Christoph Hellwig <hch@infradead.org>, Jared Hulbert <jaredeh@gmail.com>,
       Nick Piggin <nickpiggin@yahoo.com.au>,
       Andrew Morton <akpm@linux-foundation.org>,
       richard.griffiths@windriver.com,
       Richard Griffiths <res07ml0@verizon.net>, Linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2.6.21] cramfs: add cramfs Linear XIP
Message-ID: <20070607193844.GB17144@infradead.org>
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On Thu, Jun 07, 2007 at 07:07:54PM +0200, Carsten Otte wrote:
> I've had a few beer long discussion with Joern Engel and David 
> Woodhouse on this one. To cut a long discussion short: the current XIP 
> infrastructure is not sufficient to be used on top of mtd. We'd need 
> some extenstions:
> - on get_xip_page() we'd need to state if we want the reference 
> read-only or read+write
> - we need a put_xip_page() to return references
> - and finally we need a callback for the referece, so that the mtd 
> driver can ask to get its reference back (in order to unmap from 
> userland when erasing a block)

And we'll need that even when using cramfs.  There's not way we'd
merge a hack where the user has to specify a physical address on
the mount command line.

> While I fully agree, that a flash filesystem using xip would be very 
> desireable, the proposed cramfs extension is a totaly different beast 
> that has its own value to me: the ability to select per file whether 
> xip or compression is more efficient.

You'd of course want all that for a full flash filesystem aswell.
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