On Tue, Apr 28, 2020 at 02:13:48PM -0700, Douglas Anderson wrote:
> The recent patch ("kgdboc: Add kgdboc_earlycon to support early kgdb
> using boot consoles") adds a new kernel command line parameter.
> Document it.
>
> Note that the patch adding the feature does some comparing/contrasting
> of "kgdboc_earlycon" vs. the existing "ekgdboc". See that patch for
> more details, but briefly "ekgdboc" can be used _instead_ of "kgdboc"
> and just makes "kgdboc" do its normal initialization early (only works
> if your tty driver is already ready). The new "kgdboc_earlycon" works
> in combination with "kgdboc" and is backed by boot consoles.
>
> Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
> Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> ---
>
> Changes in v3:
> - Added example in kgdb.rst
> - Removed unneeded sentence in kerenel-parameters doc.
> - Renamed earlycon_kgdboc to kgdboc_earlycon.
> - Suggest people use kgdboc_earlycon instead of ekgdboc.
>
> Changes in v2: None
>
> .../admin-guide/kernel-parameters.txt | 20 ++++++++++++++++
> Documentation/dev-tools/kgdb.rst | 24 +++++++++++++++++++
> 2 files changed, 44 insertions(+)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 7bc83f3d9bdf..3b5ae06a98aa 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -1190,6 +1190,11 @@
> This is designed to be used in conjunction with
> the boot argument: earlyprintk=vga
>
> + This parameter works in place of the kgdboc parameter
> + but can only be used if the backing tty is available
> + very early in the boot process. For early debugging
> + via a serial port see kgdboc_earlycon instead.
> +
> edd= [EDD]
> Format: {"off" | "on" | "skip[mbr]"}
>
> @@ -2105,6 +2110,21 @@
> kms, kbd format: kms,kbd
> kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
>
> + kgdboc_earlycon= [KGDB,HW]
> + If the boot console provides the ability to read
> + characters and can work in polling mode, you can use
> + this parameter to tell kgdb to use it as a backend
> + until the normal console is registered. Intended to
> + be used together with the kgdboc parameter which
> + specifies the normal console to transition to.
> +
> + The the name of the early console should be specified
s/The the/The/
Other than that:
Reviewed-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
