Broadcom DNX

The DNX generator builds a single flat map of SOC properties, each with a string key and a string value. All settings are written to the common section of the output, which is described in Output structure.

The shared design is described in the Overview.

Generation pipeline

Order	Setting	Source
1	Base SDK settings	asic_vendors/broadcom/dnx/asics/<asic>.json (base_sdk_settings)
2	Declarative tables for port speeds, TM port headers, DTM flow regions, and flow remote cores	asic_vendors/broadcom/dnx/asics/<asic>.json (declarative_tables)
3	Platform SDK overrides	platforms/<system_vendor>/<platform>/asic_config/asic_config.json (platform_sdk_overrides)
4	Lane and polarity keys	computed from platform_mapping_v2 connections and the ASIC core_types, key_formats, and num_lanes_per_core, plus the ASIC default_polarity_settings
5	Conditional settings, ASIC entries then platform entries, each in array order	asic_vendors/broadcom/dnx/asics/<asic>.json (conditional_settings), then platforms/<system_vendor>/<platform>/asic_config/asic_config.json (conditional_settings)

The lane and polarity keys in step 4 reproduce the wiring that asic_config_v2 computed in per-platform Python code. The generator iterates the platform's platform_mapping_v2 connections and keeps the connection ends whose core type the ASIC declares in core_types. For each remaining connection it computes the SOC lane number as core_id * num_lanes_per_core + core_lane and renders each key through the ASIC's key_formats strings. Core types that are not declared, for example the Jericho 3 recycle and eventor ports, are skipped automatically.

Output structure

The DNX output file is the JSON representation of the thrift AsicConfig struct, which is defined in fboss/agent/hw/config/asic_config_v2.thrift. The struct consists of a common entry holding a key/value config map, together with an optional npuEntries map for platforms with more than one NPU. The platform file declares which structure to produce through the top-level output_structure field:

"output_structure": {"mode": "common_only"}

• The common_only mode is for single-NPU platforms such as meru800bia. Every generated key is written to common.config. This is the only supported mode.
• Support for multi-NPU platforms, which distribute the per-chip wiring keys for lanes and polarity into per-NPU sections while the chip-independent settings remain in common.config, is planned as a further mode.

The number of NPUs is a property of the board rather than of the ASIC, which is why output_structure is declared in the platform file and not in the per-ASIC file.

ASIC data

The per-ASIC file, for example fboss/configs/asic_vendors/broadcom/dnx/asics/jericho3.json, declares the data intrinsic to the chip. It contains the following groups of fields.

• Key formats and suffixes. The asic_suffix value, for example BCM8889X, is appended to generated SOC keys. The key_formats object holds the format strings for the lane map and polarity keys, with {family}, {lane}, and {suffix} placeholders. The core_types object maps each platform_mapping_v2 core type the chip exposes, for example J3_NIF and J3_FE, to the key families used when rendering its wiring keys.
• Base SDK settings. The base_sdk_settings map holds the SDK settings emitted for every platform and variant of this chip. Keys carry their SOC suffix inline.
• Default polarity settings. The default_polarity_settings map holds the default polarity keys that carry no lane number. Jericho 3 emits them. An ASIC without such keys omits the field.
• Declarative tables. These are described in the next section.

Declarative tables

Declarative tables capture the fixed tables that asic_config_v2 generated in per-ASIC Python code:

Table	Emits	Notes
port_speed_map	port_init_speed_* keys	Interface-type-to-speed entries, emitted verbatim.
tm_port_headers	tm_port_header_type_{in,out}_* keys	Emitted verbatim for every variant. Topology-specific header sets are selected through conditional settings.
dtm_flow_region_map	dtm_flow_mapping_mode_region_<N> keys	Expanded from key_format, start_region, count, and value.
flow_remote_cores	dtm_flow_nof_remote_cores_region* keys	Emitted verbatim.