Prefer evicting control functions that would lose address contention#685
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Prefer evicting control functions that would lose address contention#685ad3154 wants to merge 1 commit into
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This change modifies the behavior of our address claiming process to more readily evict a control function on the bus from its address if our internal control function would win contention. Previously we were being "nice" and always finding an open address. Although our earlier behavior was supported by the "Build an address table" section of ISO 11783-5, This change will improve an internal control function's ability to be placed at a desired address. This flexibility is probably good, but if you have low quality J1939 devices that fail to properly do the address claim process, you might still want to avoid conflicting with them in your preferred address.
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Describe your changes
This change modifies the behavior of our address claiming process to more readily evict a control function on the bus from its address if our internal control function would win contention. Previously we were being "nice" and always finding an open address. Although our earlier behavior was supported by the "Build an address table" section of ISO 11783-5, This change will improve an internal control function's ability to be placed at a desired address. This flexibility is probably good, but if you have low quality J1939 devices that fail to properly do the address claim process, you might still want to avoid conflicting with them in your preferred address.
As always, you can pass the null address (or nothing) as your preferred address to just arbitrate an address, which is usually the most interoperable choice and "nicest" for others on the bus.
How has this been tested?
Added a bespoke unit test for this condition