Re: squashfs on top of ubi

[Ezequiel Garcia <ezequiel.garcia@free-electrons.com>]

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On 11/04/2014 01:12 AM, Dragan Marinkovic wrote:
[..] I was able to back port the changes ​to​ Linux 3.4 and managed
> to get ubiblkvol userlan​d​ tool up and running. So far, so good.
> 

Great! :)

> I have a few questions though​:
> * What is the mechanics of actually adding squashfs image on top of UBI and
> mount it from userland? I have monolithic kernel.
> 

Well, once you have an ubiblock0_0 device it's just like any other block
device. The raw UBI volume and the block device are 1:1 so you can write
an image to the ubi0_0 volume and you'll be able to mount through the
block device:

mount -o,ro /dev/ubiblock0_0 /mnt

I have some notes with a sort of howto here waiting to be published, let
me see if I can get it in shape.

> * The current version of the driver is RO. I found some of your work from
> 2012 which introduces read-write ubiblock driver (
> http://lists.infradead.org/pipermail/linux-mtd/2012-December/045274.html).
> Is this something that could be potentially used? There is also
> http://webcache.googleusercontent.com/search?q=cache:http://patchwork.ozlabs.org/patch/323628/
> which seems to indicate that there are two separate versions of ubi block
> driver. With the exception of th​at​ post, I can't find any other reference to RW ubiblock driver.
> Could you shed some light on this?
> 

You can find the history and evolution of this driver in this cover letter:

http://lists.infradead.org/pipermail/linux-mtd/2014-February/052228.html

As you can see at some point we decided to remove write support.

-- 
Ezequiel García, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com


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