"Filing" this bug report on linaro-dev for now, so I don't forget it.
I can't figure out how to file a but against linaro-overlay on launchpad.
(Any suggestions?)

Cheers
---Dave

 --

linaro-overlay: auto-serial-console clobbers bootup serial port configuration

auto-serial-console makes incorrect assumptions about the contents of the 
kernel console= command-line paramter (compare auto-serial-console with 
linux/Documentation/kernel-parameters.txt)

This means that booting a kernel with a console= argument which has no explicit 
speed or which has other unusual settings, auto-serial-console may mess up the 
serial port when it calls getty, especially if the initial serial port speed is 
not 115200 baud.  The kernel itself does not require all serial port parameters 
to be specified on the command-line: in that case, the setup done by the 
bootloader is simply used as-is.

auto-serial-console does not determine the actual port speed if the kernel 
command-line has no explicit speed; instead it just defaults to 115200.

The simplest fix is simply not to set the relevant serial port communication 
parameters when initialising the terminal.  This should be a more robust 
solution, and would allow auto-serial-console to be simpified.  Unfortunately, 
util-linux's agetty (the default getty for Ubuntu and linaro filesystems) 
always sets these parameters explicitly.  This is an arguable misfeature and 
could probably be solved with a simple patch.  Alternatively, it would be worth 
investigating whether one of the other existing getty variants will already do 
the desired thing.

An alternative workaround could be to use stty to read the current parameters 
of the serial port, and use this information to pass the appropriate arguments 
to getty.  This may be fragile though, since stty does not produce reliably 
parseable output; the only options are to produce output which is 
human-readable, and output which is only readable by stty itself.

This bug does not affect the linaro releases directly, but can affect the use 
of Linaro filesystems with unsupported boards or custom kernel setups, 
particularly where the board's boot-time serial port speed is not 115200 such 
as on vexpress.


_______________________________________________
linaro-dev mailing list
linaro-dev@lists.linaro.org
http://lists.linaro.org/mailman/listinfo/linaro-dev

Reply via email to