Console buffer size

Chris Johns chrisj at
Wed Mar 18 23:29:33 UTC 2009

Michael Hamel wrote:
> My BSP uses the standard 16550 driver found in ../powerpc/shared/ 
> console, which seems to hook in to the termios code in cpukit/ 
> libcsupport/src. After some searching it looks as though the code is  
> interrupt-driven, but is limited to a rather small buffer size which  
> is hard-coded in that file as rtems_termios_raw_output_size. The baud  
> rate is also hard coded as 9600 in console_first_open() in console.c.
> The limitations of my debugger mean that I use console debugging  
> rather a lot and as I'm not at all short of RAM I would like to use a  
> much larger buffer and higher baud rates so that generating log  
> information doesn't suspend my tasks while they wait for the UART. I'm  
> sure that editing the shared termios.c and console.c isn't the right  
> way to do this(!)
> Is there some appropriate way of configuring the console buffer size  
> (and baud rate) in bsp.h, or some way of calling the termios code to  
> get the rate changed and buffer resized at startup? I can't find any  
> documentation or examples that seem to cover this...

Yes nothing I see covers the set up call. It is 'rtems_termios_bufsize' and 
defined in libio_.h in cpukit/libcsupport.

You need to make this call before the console is opened. You cannot change the 
settings once the driver has initialised.


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