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The chosen node
---------------
The chosen node does not represent a real device, but serves as a place
for passing data between firmware and the operating system, like boot
arguments. Data in the chosen node does not represent the hardware.
stdout-path property
--------------------
Device trees may specify the device to be used for boot console output
with a stdout-path property under /chosen, as described in ePAPR, e.g.
/ {
chosen {
stdout-path = "/serial@f00:115200";
};
serial@f00 {
compatible = "vendor,some-uart";
reg = <0xf00 0x10>;
};
};
If the character ":" is present in the value, this terminates the path.
The meaning of any characters following the ":" is device-specific, and
must be specified in the relevant binding documentation.
For UART devices, the preferred binding is a string in the form:
<baud>{<parity>{<bits>{<flow>}}}
where
baud - baud rate in decimal
parity - 'n' (none), 'o', (odd) or 'e' (even)
bits - number of data bits
flow - 'r' (rts)
For example: 115200n8r
Implementation note: Linux will look for the property "linux,stdout-path" or
on PowerPC "stdout" if "stdout-path" is not found. However, the
"linux,stdout-path" and "stdout" properties are deprecated. New platforms
should only use the "stdout-path" property.
linux,booted-from-kexec
-----------------------
This property is set (currently only on PowerPC, and only needed on
book3e) by some versions of kexec-tools to tell the new kernel that it
is being booted by kexec, as the booting environment may differ (e.g.
a different secondary CPU release mechanism)
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