Document the console option for DEVNAME:0.0 style addressing for serial
ports.

Suggested-by: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>
---
 .../admin-guide/kernel-parameters.txt         | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -785,6 +785,25 @@
 			Documentation/networking/netconsole.rst for an
 			alternative.
 
+		<DEVNAME>:<n>.<n>[,options]
+			Use the specified serial port on the serial core bus.
+			The addressing uses DEVNAME of the physical serial port
+			device, followed by the serial core controller instance,
+			and the serial port instance. The options are the same
+			as documented for the ttyS addressing above.
+
+			The mapping of the serial ports to the tty instances
+			can be viewed with:
+
+			$ ls -d /sys/bus/serial-base/devices/*:*.*/tty/*
+			/sys/bus/serial-base/devices/00:04:0.0/tty/ttyS0
+
+			In the above example, the console can be addressed with
+			console=00:04:0.0. Note that a console addressed this
+			way will only get added when the related device driver
+			is ready. The use of an earlycon parameter in addition to
+			the console may be desired for console output early on.
+
 		uart[8250],io,<addr>[,options]
 		uart[8250],mmio,<addr>[,options]
 		uart[8250],mmio16,<addr>[,options]
-- 
2.44.0

Hi Tony,

On Mar 27, 2024 at 12:59:41 +0200, Tony Lindgren wrote:
> Document the console option for DEVNAME:0.0 style addressing for serial
> ports.

Thanks, this will really add in more context for people unaware.

> 
> Suggested-by: Sebastian Reichel <sre@kernel.org>
> Signed-off-by: Tony Lindgren <tony@atomide.com>
> ---
>  .../admin-guide/kernel-parameters.txt         | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -785,6 +785,25 @@
>  			Documentation/networking/netconsole.rst for an
>  			alternative.
>  
> +		<DEVNAME>:<n>.<n>[,options]
> +			Use the specified serial port on the serial core bus.
> +			The addressing uses DEVNAME of the physical serial port
> +			device, followed by the serial core controller instance,
> +			and the serial port instance. The options are the same
> +			as documented for the ttyS addressing above.
> +
> +			The mapping of the serial ports to the tty instances
> +			can be viewed with:
> +
> +			$ ls -d /sys/bus/serial-base/devices/*:*.*/tty/*
> +			/sys/bus/serial-base/devices/00:04:0.0/tty/ttyS0
> +
> +			In the above example, the console can be addressed with
> +			console=00:04:0.0. Note that a console addressed this
> +			way will only get added when the related device driver
> +			is ready. The use of an earlycon parameter in addition to
> +			the console may be desired for console output early on.

Reviewed-by: Dhruva Gole <d-gole@ti.com>

-- 
Best regards,
Dhruva