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author | Linus Torvalds <torvalds@linux-foundation.org> | 2020-12-16 00:22:29 +0300 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-12-16 00:22:29 +0300 |
commit | d635a69dd4981cc51f90293f5f64268620ed1565 (patch) | |
tree | 5e0a758b402ea7d624c25c3a343545dd29e80f31 /Documentation/networking/j1939.rst | |
parent | ac73e3dc8acd0a3be292755db30388c3580f5674 (diff) | |
parent | efd5a1584537698220578227e6467638307c2a0b (diff) | |
download | linux-d635a69dd4981cc51f90293f5f64268620ed1565.tar.xz |
Merge tag 'net-next-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next
Pull networking updates from Jakub Kicinski:
"Core:
- support "prefer busy polling" NAPI operation mode, where we defer
softirq for some time expecting applications to periodically busy
poll
- AF_XDP: improve efficiency by more batching and hindering the
adjacency cache prefetcher
- af_packet: make packet_fanout.arr size configurable up to 64K
- tcp: optimize TCP zero copy receive in presence of partial or
unaligned reads making zero copy a performance win for much smaller
messages
- XDP: add bulk APIs for returning / freeing frames
- sched: support fragmenting IP packets as they come out of conntrack
- net: allow virtual netdevs to forward UDP L4 and fraglist GSO skbs
BPF:
- BPF switch from crude rlimit-based to memcg-based memory accounting
- BPF type format information for kernel modules and related tracing
enhancements
- BPF implement task local storage for BPF LSM
- allow the FENTRY/FEXIT/RAW_TP tracing programs to use
bpf_sk_storage
Protocols:
- mptcp: improve multiple xmit streams support, memory accounting and
many smaller improvements
- TLS: support CHACHA20-POLY1305 cipher
- seg6: add support for SRv6 End.DT4/DT6 behavior
- sctp: Implement RFC 6951: UDP Encapsulation of SCTP
- ppp_generic: add ability to bridge channels directly
- bridge: Connectivity Fault Management (CFM) support as is defined
in IEEE 802.1Q section 12.14.
Drivers:
- mlx5: make use of the new auxiliary bus to organize the driver
internals
- mlx5: more accurate port TX timestamping support
- mlxsw:
- improve the efficiency of offloaded next hop updates by using
the new nexthop object API
- support blackhole nexthops
- support IEEE 802.1ad (Q-in-Q) bridging
- rtw88: major bluetooth co-existance improvements
- iwlwifi: support new 6 GHz frequency band
- ath11k: Fast Initial Link Setup (FILS)
- mt7915: dual band concurrent (DBDC) support
- net: ipa: add basic support for IPA v4.5
Refactor:
- a few pieces of in_interrupt() cleanup work from Sebastian Andrzej
Siewior
- phy: add support for shared interrupts; get rid of multiple driver
APIs and have the drivers write a full IRQ handler, slight growth
of driver code should be compensated by the simpler API which also
allows shared IRQs
- add common code for handling netdev per-cpu counters
- move TX packet re-allocation from Ethernet switch tag drivers to a
central place
- improve efficiency and rename nla_strlcpy
- number of W=1 warning cleanups as we now catch those in a patchwork
build bot
Old code removal:
- wan: delete the DLCI / SDLA drivers
- wimax: move to staging
- wifi: remove old WDS wifi bridging support"
* tag 'net-next-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1922 commits)
net: hns3: fix expression that is currently always true
net: fix proc_fs init handling in af_packet and tls
nfc: pn533: convert comma to semicolon
af_vsock: Assign the vsock transport considering the vsock address flags
af_vsock: Set VMADDR_FLAG_TO_HOST flag on the receive path
vsock_addr: Check for supported flag values
vm_sockets: Add VMADDR_FLAG_TO_HOST vsock flag
vm_sockets: Add flags field in the vsock address data structure
net: Disable NETIF_F_HW_TLS_TX when HW_CSUM is disabled
tcp: Add logic to check for SYN w/ data in tcp_simple_retransmit
net: mscc: ocelot: install MAC addresses in .ndo_set_rx_mode from process context
nfc: s3fwrn5: Release the nfc firmware
net: vxget: clean up sparse warnings
mlxsw: spectrum_router: Use eXtended mezzanine to offload IPv4 router
mlxsw: spectrum: Set KVH XLT cache mode for Spectrum2/3
mlxsw: spectrum_router_xm: Introduce basic XM cache flushing
mlxsw: reg: Add Router LPM Cache Enable Register
mlxsw: reg: Add Router LPM Cache ML Delete Register
mlxsw: spectrum_router_xm: Implement L-value tracking for M-index
mlxsw: reg: Add XM Router M Table Register
...
Diffstat (limited to 'Documentation/networking/j1939.rst')
-rw-r--r-- | Documentation/networking/j1939.rst | 46 |
1 files changed, 42 insertions, 4 deletions
diff --git a/Documentation/networking/j1939.rst b/Documentation/networking/j1939.rst index 0a4b73b03b99..b705d2801e9c 100644 --- a/Documentation/networking/j1939.rst +++ b/Documentation/networking/j1939.rst @@ -69,18 +69,56 @@ J1939 concepts PGN --- +The J1939 protocol uses the 29-bit CAN identifier with the following structure: + + ============ ============== ==================== + 29 bit CAN-ID + -------------------------------------------------- + Bit positions within the CAN-ID + -------------------------------------------------- + 28 ... 26 25 ... 8 7 ... 0 + ============ ============== ==================== + Priority PGN SA (Source Address) + ============ ============== ==================== + The PGN (Parameter Group Number) is a number to identify a packet. The PGN is composed as follows: -1 bit : Reserved Bit -1 bit : Data Page -8 bits : PF (PDU Format) -8 bits : PS (PDU Specific) + + ============ ============== ================= ================= + PGN + ------------------------------------------------------------------ + Bit positions within the CAN-ID + ------------------------------------------------------------------ + 25 24 23 ... 16 15 ... 8 + ============ ============== ================= ================= + R (Reserved) DP (Data Page) PF (PDU Format) PS (PDU Specific) + ============ ============== ================= ================= In J1939-21 distinction is made between PDU1 format (where PF < 240) and PDU2 format (where PF >= 240). Furthermore, when using the PDU2 format, the PS-field contains a so-called Group Extension, which is part of the PGN. When using PDU2 format, the Group Extension is set in the PS-field. + ============== ======================== + PDU1 Format (specific) (peer to peer) + ---------------------------------------- + Bit positions within the CAN-ID + ---------------------------------------- + 23 ... 16 15 ... 8 + ============== ======================== + 00h ... EFh DA (Destination address) + ============== ======================== + + ============== ======================== + PDU2 Format (global) (broadcast) + ---------------------------------------- + Bit positions within the CAN-ID + ---------------------------------------- + 23 ... 16 15 ... 8 + ============== ======================== + F0h ... FFh GE (Group Extenstion) + ============== ======================== + On the other hand, when using PDU1 format, the PS-field contains a so-called Destination Address, which is _not_ part of the PGN. When communicating a PGN from user space to kernel (or vice versa) and PDU2 format is used, the PS-field |