-- SSIF Get Device ID (slave 0x20) --
BWRITE cmd=2 (SSIF req)            rc= 0 errno= 0
BREAD  cmd=3 (SSIF rsp)            rc= 0 errno= 0 rcount=  3 data=06 18 00 00
-- DF-5458: uninitialized bcount gates SMB_BREAD --
fresh-process BREAD (kernel stack garbage):
  BREAD cmd=3                      rc= 0 errno= 0 rcount=  3 data=06 18 00 00
  BREAD cmd=3                      rc= 0 errno= 0 rcount=  3 data=06 18 00 00
  BREAD cmd=3                      rc= 0 errno= 0 rcount=  3 data=06 18 00 00
dirty the kernel stack with unrelated syscalls (write/read of 0x10 bytes):
  BREAD cmd=3 (post-dirty)         rc= 0 errno= 0 rcount=  3 data=06 18 00 00
prime the response, then chain reads (previous bcount self-perpetuates):
  BWRITE cmd=2 (SSIF req)          rc= 0 errno= 0
  BREAD cmd=3 (primed)             rc= 0 errno= 0 rcount=  3 data=06 18 00 00
  BREAD cmd=3 (chained)            rc= 0 errno= 0 rcount=  3 data=06 18 00 00
  BREAD cmd=3 (chained)            rc= 0 errno= 0 rcount=  3 data=06 18 00 00
  BREAD cmd=3 (chained)            rc= 0 errno= 0 rcount=  3 data=06 18 00 00
DDC read (QEMU clamps count 0xFF->0) resets slot to 0:
  BREAD slave=0x50 cmd=1           rc=-1 errno=35 rcount=1024 data=06 18 00 00
  BREAD cmd=3 (after 0)            rc= 0 errno= 0 rcount=  3 data=06 18 00 00
  BREAD cmd=3 (still 0?)           rc= 0 errno= 0 rcount=  3 data=06 18 00 00
  WRITEB slave=0x50 (depth probe)  rc= 0 errno= 0
  BREAD cmd=3 (post WRITEB)        rc= 0 errno= 0 rcount=  3 data=06 18 00 00