linux-kernel - RE: [PATCH 0/5] cramfs refresh for embedded usage

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Date:   Wed, 16 Aug 2017 15:12:09 +0000
From:   Chris Brandt <Chris.Brandt@...esas.com>
To:     Nicolas Pitre <nicolas.pitre@...aro.org>
CC:     Alexander Viro <viro@...iv.linux.org.uk>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-embedded@...r.kernel.org" <linux-embedded@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 0/5] cramfs refresh for embedded usage

On Wednesday, August 16, 2017 1, Nicolas Pitre wrote:
> > Just FYI,
> > I'm running an xipImage with all the RZ/A1 upstream drivers enabled and
> > only using about 4.5MB of total system RAM.
> > That's pretty good. Of course for a real application, you would trim off
> > the drivers and subsystems you don't plan on using, thus lowering your
> > RAM usage.
> 
> On my MMU-less test target I'm going under the 1MB mark now.

Show off  ;)


> Given that I also applied the device table patch to mkcramfs (that
> allows for the creation of device nodes and arbitrary
> user/group/permission without being root) it would be possible to extend
> this mechanism to implement other XIP patterns such as for
> uncompressible media files for example.

Good, I was going to ask about that.

I made an example once were all the graphics were RAW and uncompressed 
and marked as XIP in AXFS. The result was a large saving of RAM because 
as the graphics framework (DirectFB) would copy directly from Flash 
whenever it needed to do a background erase or image re-draw (button press 
animations).

Same went for playing MP3 files. The MP3 files were XIP in flash, so 
mpg123 pulled from flash directly.


Chris