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From: Eugene Surovegin <ebs@ebshome.net>
To: colin <colin@realtek.com.tw>
Cc: linux-mips@linux-mips.org
Subject: Re: Strange! Cannot use JFFS2 as root
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On Wed, Oct 20, 2004 at 10:02:26PM +0800, colin wrote:
> 
> Hi all,
> I had booted up Linux with nfs root, and write a JFFS2 image to /dev/mtd1.
> Here is my cmdline for Kernel:
>      go 0x80305018 root=/dev/nfs rw nfsroot=172.19.26.145:/nfs/rootfs
> ip=172.19.27.193::172.19.27.254:255.255.254.0:::
> mtdparts=maltaflash:1536k(ldr),2048k(root)
> 
> After writing the JFFS2 image to /dev/mtd1, I can mount /dev/mtdblcok1 to
> some directory.
>     mount -t jffs2 /dev/mtdblock1 /mnt
> 
> Next, I hope to boot up Linux with JFFS2 root, and try to give this cmdline
> to Kernel:
>     go 0x80305018 rootfstype=jffs2
> mtdparts=maltaflash:1536k(ldr),2048k(root) root=/dev/mtdblock1
> 
> and the Kernel would complain me about no root:
>     VFS: Unable to mount root fs via NFS, trying floppy.
>     Kernel panic: VFS: Unable to mount root fs on unknown-block(2,0)
> 
> I traced the code and found that when passing "/dev/mtdblock1" to
> name_to_dev_t() in do_mounts.c, it would return 0 at every try_name(),
>  which will fail at open() with the path "/sys/block/%s/dev".
> 
> What's the problem? Could anyone tell me?

What is the kernel version you are using?

Check that root_dev_names array in init/do_mounts.c has an entry, 
which looks like

	{ "mtdblock", 0x1f00 }

--
Eugene