• Devid Antonio Filoni's avatar
    can: j1939: do not wait 250 ms if the same addr was already claimed · 4ae5e1e9
    Devid Antonio Filoni authored
    The ISO 11783-5 standard, in "4.5.2 - Address claim requirements", states:
      d) No CF shall begin, or resume, transmission on the network until 250
         ms after it has successfully claimed an address except when
         responding to a request for address-claimed.
    
    But "Figure 6" and "Figure 7" in "4.5.4.2 - Address-claim
    prioritization" show that the CF begins the transmission after 250 ms
    from the first AC (address-claimed) message even if it sends another AC
    message during that time window to resolve the address contention with
    another CF.
    
    As stated in "4.4.2.3 - Address-claimed message":
      In order to successfully claim an address, the CF sending an address
      claimed message shall not receive a contending claim from another CF
      for at least 250 ms.
    
    As stated in "4.4.3.2 - NAME management (NM) message":
      1) A commanding CF can
         d) request that a CF with a specified NAME transmit the address-
            claimed message with its current NAME.
      2) A target CF shall
         d) send an address-claimed message in response to a request for a
            matching NAME
    
    Taking the above arguments into account, the 250 ms wait is requested
    only during network initialization.
    
    Do not restart the timer on AC message if both the NAME and the address
    match and so if the address has already been claimed (timer has expired)
    or the AC message has been sent to resolve the contention with another
    CF (timer is still running).
    Signed-off-by: default avatarDevid Antonio Filoni <devid.filoni@egluetechnologies.com>
    Acked-by: default avatarOleksij Rempel <o.rempel@pengutronix.de>
    Link: https://lore.kernel.org/all/20221125170418.34575-1-devid.filoni@egluetechnologies.com
    Fixes: 9d71dd0c ("can: add support of SAE J1939 protocol")
    Cc: stable@vger.kernel.org
    Signed-off-by: default avatarMarc Kleine-Budde <mkl@pengutronix.de>
    4ae5e1e9
address-claim.c 7.84 KB