[PATCH v7 7/7] Documentation: kernel-parameters: Add DEVNAME:0.0 format for serial ports

Tony Lindgren
2024-03-27T11:06:18Z

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