t_dma said "p1 len 0x0002 implausible (RWP=11)", which names the symptom but
not the cause: a length alone cannot distinguish an unwritten descriptor from a
shifted read from a frame written at a page other than the one RRP points at.
On failure it now walks all 15 ring pages, classifies each descriptor ('-'
all-zero/never written, 'o' plausible length, 'x' non-zero but implausible,
'?' read failed) and prints that map plus the 4 raw descriptor bytes at the RRP
page. One run then shows which of those it is.
Diagnostic only; no change to the pass/fail criterion or to any gateware.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Roflin
e20b34b5e9