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30 lines
1.5 KiB
Markdown
30 lines
1.5 KiB
Markdown
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# Non-volatile Memory - Data Repositories
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This area is intentionally structured in the following way:
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```
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╰- quantum
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╰- nvm
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├- readme.md
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├- rules.mk
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├- nvm_eeconfig.h
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├- nvm_<<system>>.h
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├- eeprom
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| ├- nvm_eeconfig.c
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| ├- nvm_<<system>>.c
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| ╰- ...
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├- <<another provider>>
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| ├- nvm_eeconfig.c
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| ├- nvm_<<system>>.c
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| ╰- ...
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╰- ...
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```
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At the base `nvm` level, for every QMK core system which requires persistence there must be a corresponding `nvm_<<system>>.h` header file. This provides the data repository API to the "owner" system, and allows the underlying data persistence mechanism to be abstracted away from upper code. Any conversion to/from a `.raw` field should occur inside the `nvm_<<system>>.c` layer, with the API using values, such as structs or unions exposed to the rest of QMK.
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Each `nvm` "provider" is a corresponding child directory consisting of its name, such as `eeprom`, and corresponding `nvm_<<system>>.c` implementation files which provide the concrete implementation of the upper `nvm_<<system>>.h`.
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New systems requiring persistence can add the corresponding `nvm_<<system>>.h` file, and in most circumstances must also implement equivalent `nvm_<<system>>.c` files for every `nvm` provider. If persistence is not possible for that system, a `nvm_<<system>>.c` file with simple stubs which ignore writes and provide sane defaults must be used instead.
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