The maximum number of ring slots a tx packet can use is 32, which is

The maximum number of ring slots a tx packet can use is 32, which is
indicated by writing 0 to the 5 bit 'BD count' field in the first slot.
Accordingly, mask the value we're writing there.

Each packet uses one slot for offload information and then one per DMA
segment, which means the maximum number of DMA segments must be 31 rather
than 32.  Trying to send a packet using 33 slots makes the nic firmware
very upset.

ok dlg@