https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=15454
--- Comment #7 from Maksim Salau <maksim.sa...@gmail.com> ---
Hi Michael,
> What exactly is this and what other Wireshark constructs would you equate it
> to?
The dissector is for decoding data payload of CAN frames. This is somewhat
similar to AUTOSAR NM "User Data Field Configuration". In AUTOSAR NM you can
define how to interpret data payload, but in this dissector one can define
payload format for any CAN frame based on its id.
Usage scenarios for the dissector are CAN buses that don't make use of standard
protocols like CANopen or J1939.
> Is this similar to ASN.1 definitions where you want a "dbc to dissector"
> tool that will generate a C code dissector from the data in the .dbc file?
> (that in this case would register handlers for the j1939.pgn dissector
> table)
This dissector has J1939 file type support but it only partially overlap with
it. The J1939 dissector decodes only CAN id, but not data, while this dissector
aims at data and uses id only to pick correct spec from a DBC file.
> Is this supposed to be dynamically loaded at runtime and the J1939 dissector
> would create a "database of hf_ fields" based on the information in the .dbc
> file(s)?
Yes, the spec is loaded in runtime. And 'no' - this dissector doesn't make use
of the J1939 subdissector but acts on its own.
'J1939' in this dissector is only used to define 2 ways of interpreting ids:
1. full id match;
2. masked (only J1939 type PGN should match).
> Is there a DBC spec that explains the fields in the file?
Unfortunately there is no official spec of the file format, but there are a
number of open-source tools [1]..[5] that may used as a reference.
Since spec is not available, parser is much more forgiving than the official
tool: CANdb++ Editor by Vector Informatik GmbH.
The parser is implemented by hand, possibly it should be rewritten to make use
of flex & bison.
[1] https://github.com/rbei-etas/busmaster/
[2] https://github.com/ebroecker/canmatrix/
[3] https://bitbucket.org/tobylorenz/vector_dbc/
[4] https://github.com/collin80/SavvyCAN/
[5] https://github.com/eerimoq/cantools/
--
You are receiving this mail because:
You are watching all bug changes.
___________________________________________________________________________
Sent via: Wireshark-bugs mailing list <wireshark-bugs@wireshark.org>
Archives: https://www.wireshark.org/lists/wireshark-bugs
Unsubscribe: https://www.wireshark.org/mailman/options/wireshark-bugs
mailto:wireshark-bugs-requ...@wireshark.org?subject=unsubscribe
