Handling of short frames in gem(4) (was: CVS commit: src/sys/dev/ic)

[Matthias Scheler <tron%NetBSD.org@localhost>]

On Mon, Dec 31, 2007 at 08:54:43PM +0000, David Young wrote:
> Module Name:  src
> Committed By: dyoung
> Date:         Mon Dec 31 20:54:43 UTC 2007
> 
> Modified Files:
>       src/sys/dev/ic: gem.c
> 
> Log Message:
> gem_start() pads a Tx packet to the minimum ethernet frame length
> by adding a segment to the Tx chain.  That entails using one more
> descriptor.  It did not synchronize the last descriptor.
> 
> In gem_start(), clarify and repair DMA synchronization of the Tx
> descriptors.  Sync them all.

Wouldn't it be cheaper (and simpler) to allocate a new mbuf and copy
the data? IIRC DMA operations are quite expensive on UltraSPARC systems.

        Kind regards

-- 
Matthias Scheler                                  http://zhadum.org.uk/