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