How to change root device on L4 Linux ?

Matthias Lange matthias.lange at
Tue Apr 1 14:23:22 CEST 2014


On Tue, Apr 01, 2014 at 07:07:44PM +0900, Taeung wrote:
> Hello, L4 hackers :-)
> I want to change *root device* on L4 Linux instead of ramdisk.
> Root device I want is like '*/dev/mtdblock0*' or '/dev/mmcblk1p1'
> instead of 'rom/ramdisk-arm.rd'.
> So, I've configured somethings in 'L4 Linux menuconfig', additionally.
> Somethings are as follows ..
> ==============================
> <*> MMC/SD/SDIO card support  --->
> <*> The Extended 4 (ext4) filesystem
>  [*]   Ext4 POSIX Access Control Lists
>  [*]   Ext4 Security Labels
> ==============================
> kernel command line : "rom/vmlinuz.arm console=ttyLv0
> root=/dev/mtdblock0 rootwait rw "
> ==============================
> But it is hangs at '*Waiting for root device /dev/mtdblock0...*'.
> I've heard that the solution of this is to pass-through the physical MMC device to L4Linux.
> Please, tell me it's concrete ways or hints about what I must study for solving this.
> I can't even guess what the solution mean.. please.

First you need to identify the native Linux driver for the SD controller. Then
you need to identify all the resources (IO memory, GPIO pins, IRQs, clocks,
...) the driver requires. Then you need to make those resources available to
L4Linux. Most likely you have to define a custom L4Linux ARM platform and
create a platform file which defines all devices for it. Then the first step
is to get the SD driver successfully pass the probe function.


Matthias Lange, matthias.lange at, +49 - 351 - 41 88 86 14

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