The driver advertises SMBus byte and word writes but no write to a real
device had been exercised in this cycle. Engine-level evidence existed -- a
write to an unpopulated address returns -ENXIO with the address NACK
reported, so writes are issued rather than suppressed -- but nothing showed
a populated device accepting one.
Driven through the sibling project's CLI, which uses the framing decoded in
its own protocol notes: a 12-write frame to the LED controller at 0x27 on
both channels, latch open, effect id, brightness, three colour bytes, latch
commit. Every write acknowledged, no NACK, no interference reported, and
the device applied the result.
This also settles SMB_DIS_WRT, which is set in the documented SMBCNTL and
is SMM-writable only: it governs the documented interface, not this path.
No SPD was written at any point. The four SPD EEPROMs were verified present
with valid CRCs before and after every experiment in this cycle.
Simone
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