Metadata handling#

group Metadata handling

Handle JSON-formatted metadata.

Enums

enum jsdrv_meta_flag_e#

Metadata flag bits (mirrors minibitty’s mb_pubsub_meta_flags_e).

Values:

enumerator JSDRV_META_FLAG_RO#

Topic is read-only; cannot be updated by the host.

enumerator JSDRV_META_FLAG_HIDE#

Topic should not appear in the user interface.

enumerator JSDRV_META_FLAG_DEV#

Developer option; not for production use.

Functions

int32_t jsdrv_meta_syntax_check(const char *meta)#

Check the JSON metadata syntax.

Parameters:

meta – The JSON metadata.

Returns:

0 or error code.

int32_t jsdrv_meta_dtype(const char *meta, uint8_t *dtype)#

Get the data type.

Parameters:

  • meta – The JSON metadata.

  • dtype – [out] The jsdrv_union_e data type.

Returns:

0 or error code.

int32_t jsdrv_meta_default(const char *meta, struct jsdrv_union_s *value)#

Get the default value.

Parameters:

  • meta – The JSON metadata.

  • value – [out] The parsed default value.

Returns:

0 or error code.

int32_t jsdrv_meta_value(const char *meta, struct jsdrv_union_s *value)#

Validate a parameter value using the metadata.

Parameters:

  • meta – The JSON metadata.

  • value – [inout] The value, which is modified in place.

Returns:

0 or error code.

int32_t jsdrv_meta_flags(const char *meta, uint32_t *flags)#

Get the flags bitmask from the metadata.

Parses the “flags” key from the JSON metadata, which is a list of string tokens: “ro”, “hide”, “dev”. Returns a bitmask of jsdrv_meta_flag_e. If “flags” is absent, *flags is set to 0.

Parameters:

  • meta – The JSON metadata.

  • flags – [out] The resulting bitmask.

Returns:

0 or error code.

Host-side metadata#

The driver defines its own topic metadata, such as JS320 h/fs and the memory buffer m/ topics, in jsdrvp_param_s tables in src/**/*_params.c. Tables in src/devices/<model>/ apply to that device model. Other tables are global driver topics. Topics may contain {buf} and {sig} placeholders for the buffer and signal ids.

pyjoulescope_driver.metadata_extract parses these tables into the packaged host_params.json. After editing a table, regenerate it with:

python -m pyjoulescope_driver.metadata_extract --write

A unit test fails when host_params.json is stale.

The metadata entry point combines this host-side metadata with the firmware build’s pubsub_metadata.json files to document all topics without a device:

python -m pyjoulescope_driver metadata --firmware js320.zip --out js320.html

With a connected device, --diff compares the live metadata against a saved JSON file to verify the offline output:

python -m pyjoulescope_driver metadata --diff js320.json