iflib: Use a single tx dma mapHEADmain

The need for a separate map for TSO and non-TSO seems to have arisen from
a misunderstanding about the DMA requirements for Intel drivers like
ice/ixl/iavf. Specifically, this Intel hardware has a quirk where no
more than N (=8) segs can be DMA'ed per packet on the wire. This limit
was enforced using a DMA map with a low segment limit for non-TSO and a
driver specific check for TSO. This led to a *lot* of complexity in
iflib (~80 extra lines of code that this change removes) when the
limit can simply be enforced via the existing EFBIG mechanisms.

This change adds a new flag, IFLIB_SPARSE_TX, that drivers for hardware
with this quirk must set.  When set, it causes non-TSO sends that
exceed isc_tx_nsegment to be treated as if bus_dmamap_load_mbuf_sg()
had returned EFBIG.

Due to the API/KABI change, I've bumped the FreeBSD version as well.

Note kgalazka suggested the flag, rather than a more awkward
mechanism that I had in my initial patch.

Reviewed by: kbowling
Sponsored by: Netflix
Differential Revision:  https://reviews.freebsd.org/D60175

0 files changed, 0 insertions, 0 deletions