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authorLeif Lindholm <leif.lindholm@linaro.org>2014-11-27 17:56:05 +0000
committerGrant Likely <grant.likely@linaro.org>2014-12-03 23:12:35 +0000
commit2a9d832cc9aae21ea827520fef635b6c49a06c6d (patch)
tree6d2e3b625fc1910b1e09c3ce276859ab39177f23 /Documentation/devicetree/bindings/chosen.txt
parent63ebecc03d2f18411da51a0981bd63818bbd0b54 (diff)
of: Add bindings for chosen node, stdout-path
Add a global binding for the chosen node. Include a description of the stdout-path, and an explicit statement on its extra options in the context of a UART console. Opening description stolen from www.devicetree.org, and part of the remaining text provided by Mark Rutland. Signed-off-by: Leif Lindholm <leif.lindholm@linaro.org> [grant.likely: remove reference to uart_parse_options] Reviewed-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Grant Likely <grant.likely@linaro.org>
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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.