linux-kernel - Re: [PATCH v3 08/11] Documentation: kgdboc: Document new kgdboc

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Date:   Mon, 4 May 2020 15:40:21 +0100
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     jason.wessel@...driver.com, gregkh@...uxfoundation.org,
        agross@...nel.org, kgdb-bugreport@...ts.sourceforge.net,
        catalin.marinas@....com, linux-serial@...r.kernel.org,
        sumit.garg@...aro.org, corbet@....net, mingo@...hat.com,
        will@...nel.org, hpa@...or.com, tglx@...utronix.de,
        frowand.list@...il.com, bp@...en8.de, bjorn.andersson@...aro.org,
        jslaby@...e.com, Andrew Morton <akpm@...ux-foundation.org>,
        Juergen Gross <jgross@...e.com>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 08/11] Documentation: kgdboc: Document new
 kgdboc_earlycon parameter

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@...omium.org>
> Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> ---
> 
> 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@...aro.org>