How to mount a root FS on Flash RAM?

pub.helmutjahns_at_gmx.de
Date: 11/25/05

  • Next message: giangiammy_at_gmail.com: "Re: How to mount a root FS on Flash RAM?" 
    Date: 25 Nov 2005 05:06:32 -0800

    Hi to everybody!

    I'm using kernel version 2.6.8.1 and target is an ARM922T processor.

    I'd like to mount the root FS which is located on Flash memory instead
    of using initrd during kernel startup.

    The compilation process builds a rootfs.jffs2 which is put into the
    Flash memory at the beginning of block 0. I changed the kernel command
    string to

        root=/dev/mtdblock0 rw mem=8M noinitrd console=ttyUA0,115200
    ramdisk=3700

    which is expected to match the requirements (I was testing some
    modifications of this string, of course). I also adapted the Flash
    device driver to use the right Flash memory base address (begin of
    block 0).

    When using initrd instead, I'm able to mount the Flash device using
    shell commands, therefore I can rule out a Flash memory malfunction.

    When booting I get a kernel panic:

        VFS: Cannot open root device "mtdblock0" or unknown-block(0,0)
        Please append a correct "root=" boot option
        Kernel panic: VFS: Unable to mount root fs on unknown-block(0,0)

    It turned out to be that the device is not registered properly
    (stackframe:
    do_mount()=>do_new_mount()=>do_kern_mount()=>ext2_get_sb()=>get_sb_bdev()=>open_bdev_excl()=>blkdev_get()=>do_open()=>get_gendisk()=>kobj_lookup()
    access the wrong block device, of course using ext2_get_sb() is also
    suspicious in this case).

    The reason for the device registration malfunction can be seen in
    function filp_open() (stackframe:
    do_exit()=>init()=>prepare_namespace()=>name_to_device_t()=>try_name()=>sys_open()=>filp_open()
    ). This function receives the file name '/sys/block/mtdblock0/dev' and
    returns with error code 'no entry', indicating that this file is
    nonexistent.

    It seems to be that preparation of mounting root FS on Flash is
    incomplete. Is there anybody who can tell me what's going wrong here?

    Any help would be very appriciated!

    Thanks a lot.

  • Next message: giangiammy_at_gmail.com: "Re: How to mount a root FS on Flash RAM?"
    • Quantcast