• Stefan Richter's avatar
    firewire: fw-ohci: work around generation bug in TI controllers (fix AV/C and more) · d34316a4
    Stefan Richter authored
    Unlike the ohci1394 driver, fw-ohci uses the selfIDGeneration field of
    bus reset packets to determine the generation of incoming requests as
    per OHCI 1.1 clause 8.4.2.3.  This is more precise --- provided that the
    controller inserts the correct generation.  Texas Instruments chips
    often don't.
    
    This prevented the transmission of response packets, which for example
    broke AV/C transactions as used when communicating with miniDV cameras
    and any other AV/C devices.
    
    There is apparently no way to detect and adjust incorrect generations.
    Therefore we ignore the generation of bus reset packets from TI chips
    and use the generation of the self ID buffer instead.  Alas this is
    received at a slightly wrong time.  In rare cases, this could cause us
    to not respond to legitimate requests or to respond to expired requests.
    (The latter is less likely because the bus reset packet AR event is
    typically handled before the self ID complete event.)
    
    Bug reported by Mladen Kuntner, who was extraordinarily patient while
    dealing with the driver maintainers.  Fix confirmed to be required and
    effective for TSB82AA2 and a TSB43AB22 or TSB43AB22A.
    https://bugzilla.redhat.com/show_bug.cgi?id=243081Signed-off-by: default avatarStefan Richter <stefanr@s5r6.in-berlin.de>
    Signed-off-by: default avatarJarod Wilson <jwilson@redhat.com>
    d34316a4
fw-ohci.c 70.7 KB