sfc: Simplify TSO header buffer allocation
TSO header buffers contain a control structure immediately followed by
the packet headers, and are kept on a free list when not in use. This
complicates buffer management and tends to result in cache read misses
when we recycle such buffers (particularly if DMA-coherent memory
requires caches to be disabled).
Replace the free list with a simple mapping by descriptor index. We
know that there is always a payload descriptor between any two
descriptors with TSO header buffers, so we can allocate only one
such buffer for each two descriptors.
While we're at it, use a standard error code for allocation failure,
not -1.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
3 files changed