mac80211: allow drivers to support S/G

If drivers want to support S/G (really just gather DMA on TX) then
we can now easily support this on the fast-xmit path since it just
needs to write to the ethernet header (and already has a check for
that being possible.)

However, disallow this on the regular TX path (which has to handle
fragmentation, software crypto, etc.) by calling skb_linearize().

Also allow the related HIGHDMA since that's not interesting to the
code in mac80211 at all anyway.

Change-Id: I22edad610596a34761e4f1ae519f5fd31e0c8898
Signed-off-by: Johannes Berg <>
3 files changed