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    SubjectRe: [PATCH v9 3/3] printk: fix double printing with earlycon
    On (05/11/17 17:24), Sergey Senozhatsky wrote:
    > On (05/09/17 10:29), Sabrina Dubroca wrote:
    > [..]
    > > That's caused a change of behavior in my qemu setup, with this cmdline
    > >
    > > root=/dev/sda1 console=ttyS1 console=ttyS0
    > >
    > > Before, the kernel logs appeared on ttyS1, and I logged in with ttyS0
    > > (with my setup, ttyS1 is a file and ttyS0 is unix socket). Now, the
    > > kernel logs go to ttyS0. I need to swap the two console= parameters to
    > > restore behavior.
    > >
    > > There might be some other problem (in qemu?) though, because adding
    > > console=tty0 anywhere on that cmdline makes the logs appear on both
    > > tty0 and one ttyS* (but only one of them, and the ordering of the
    > > ttyS* matters).
    >
    > thanks for the report.
    >
    > so we have ttyS1 first and ttyS0 last.
    > after commit in question, register_console() iterates console_cmdline
    > in reverse order so we see ttyS0 first, then we hit `if (newcon->index < 0)'
    > condition, set newcon to ttyS0, because we iterate in reverse order now, and
    > break out. so we enable ttyS0, instead of ttyS1.
    >
    > previously, we iterated console_cmdline from index 0 and saw ttyS1 first.
    > so the same `if (newcon->index < 0)' condition would set newcone to ttyS1,
    > and, thus, we would enable ttyS1, not ttyS0.

    Alexey,
    can we have preferred console at offset 0 (not at console_cmdline_cnt - 1)
    and restore the previous register_console() iteration order?

    -ss

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