can one configure MCLBYTES?

Sebastian Huber sebastian.huber at
Fri Dec 14 08:32:06 UTC 2012

Hello Jeff,

On 12/14/2012 03:26 AM, Hill, Jeff wrote:
> Hi,
> The simplest way to get Jumbo frames working for the Altera TSE Mac driver would be to configure MCLBYTES to be just larger than 9000 using MCLSHIFT. Problem is, that after a quick search of the source I haven't determined how one does this. I can see that the parameters are in a generated file - parm.h, but don't know what macro one sets to change the parameter during the RTEMS build. Any hints can save some time on my end!

on our Nios 2 tool chain we have a Newlib provided param.h file.  Here we have:

#ifndef	MSIZE
#define MSIZE		128		/* size of an mbuf */
#endif	/* MSIZE */

#ifndef	MCLSHIFT
#define MCLSHIFT	11		/* convert bytes to m_buf clusters */
#endif	/* MCLSHIFT */

I would change this file in Newlib and rebuild the tool chain.  I am not sure 
if someone ever used a different value than 11 in RTEMS.

Sebastian Huber, embedded brains GmbH

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