Bug#870430: linux-image-4.9.0-3-marvell: Couldn't find DTB in /usr/lib/linux-image-4.9.0-3-marvell or /etc/flash-kernel/dtbs

[Ian Campbell <ijc@debian.org>]

On Wed, 2017-08-02 at 21:29 +0200, noone never wrote:
> Please find my answers inline.

Thanks! In particular for...

> [...]
> > The message:
> >     Couldn't find DTB  in /usr/lib/linux-image-4.9.0-3-marvell or
> > /etc/flash-kernel/dtbs
> > is interesting since the double space in "DTB  in" is supposed to
> > contain $dtb_name, i.e. the path to look for, but it doesn't not.
> > Please could you attach the full output of running `sh -x
> > /usr/sbin/flash-kernel`, maybe that will include a clue as to where
> > things have gone astray.
> 
> Log is attached 

... this.

Looking at uses of dtb in you trace:
    $ grep dtb ~/tmp/flash-kernel-log.txt
    [...]
    + dtb_name=kirkwood-sheevaplug.dtb
    + '[' -n kirkwood-sheevaplug.dtb ']'
    + echo 'Using DTB: kirkwood-sheevaplug.dtb'
    Using DTB: kirkwood-sheevaplug.dtb

So dtb_name is successfully assigned and reported here.

    + handle_dtb
    + '[' xkirkwood-sheevaplug.dtb = x ']'
    + local dtb
    + local dtb_name

But here it is redeclared as a local shadowing the original, but
unassigned.

    ++ find_dtb_file
    ++ local dtb
    ++ case "$dtb_name" in
    +++ find /etc/flash-kernel/dtbs -name
    ++ dtb=
    ++ dtb=
    ++ error 'Couldn'\''t find DTB  in /usr/lib/linux-image-4.9.0-3-marvell or /etc/flash-kernel/dtbs'
    ++ echo 'Couldn'\''t find DTB  in /usr/lib/linux-image-4.9.0-3-marvell or /etc/flash-kernel/dtbs'
    Couldn't find DTB  in /usr/lib/linux-image-4.9.0-3-marvell or /etc/flash-kernel/dtbs

    and we end up using the blank version here.

    I have a suspicious this was introduced by the fix to #836697 in [0]
    which seems to have added the shadowing "local dtb_name".

    It's a bit naughty but if you edit /usr/share/flash-kernel/functions
    and  near the top of handle_dtb() change the:
    	    local dtb
    	    local dtb_name
    into
    	    local dtb
    	    local dtb_name=$(basename $dtb_name)

    and then remove the "dtb_name=$(basename $dtb_name)" from both halves
    of the following if statement, does that fix it?

    Martin, does that fix seem correct to you?

    I think the "local dtb" bit could also move into the else have with the
    "dtb=$(find_dtb_file)" as well, but that would be an unrelated change.

    This ultimately seems to be down to a difference in the behaviour of
    /bin/dash vs /bin/bash, which I suppose is why it has not been widely
    seen:

    $ cat > t.sh <<EOF
    c() {
        echo "c.a = \"$a\""
    }

    b() {
        local a
        echo "b.a = \"$a\""
    }

    a() {
        local a=foo
        echo "a.a = \"$a\""
        b
        c
    }

    a
    EOF
    $ dash t.sh 
    a.a = "foo"
    b.a = "foo"
    c.a = "foo"
    $ bash t.sh
    a.a = "foo"
    b.a = ""
    c.a = "foo"

    I s    uppose you have /bin/sh as a link to /bin/bash on your system still.

    So an alternative workaround would probably be "sudo dpkg-reconfigure
    dash" and make dash the system shell.

        Ian.

        [0]         https://anonscm.debian.org/cgit/d-i/flash-kernel.git/commit/?id=0eb2ec06735e4a5712796836f7061190dfcf3a37