Ken Van Hoeylandt
39 lines
1.6 KiB
Markdown
39 lines
1.6 KiB
Markdown
# Architecture: Hardware Abstraction Layer
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## Driver
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A driver generally consists of:
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- Registration of driver in parent module (optional, but desirable)
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- YAML bindings in the `bindings/` folder
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- An `#include` that is used in the `.dts` file. The include is in `[projectname]/bindings/[drivername].h`
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- The driver implementation: a `.cpp` and `.h` file. The implementation is C++, but the header exposes pure C functions. C implementations are allowed, but C++ is preferred.
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Drivers are part of a kernel module.
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A driver whose device sits on a shared SPI controller (parent device type `SPI_CONTROLLER_TYPE`)
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must bracket its own bus access with `spi_controller_lock()`/`spi_controller_unlock()`
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(`spi_controller_lock_bus_of()`/`spi_controller_unlock_bus_of()` for the common case of a direct
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child), at the logical-operation level rather than per primitive. This is not done for you by the
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kernel's generic device-type wrappers (`display.cpp`, `pointer.cpp`, etc.) - only the driver knows
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for certain which of its calls touch the bus.
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Modules with drivers can be stored in:
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- TactilityKernel
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- A subproject in `Platforms` folder
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- A subproject in `Devices` folder
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- A subproject in `Drivers` folder
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## Kernel Modules
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Kernel module names are lower case and postfixed with `-module`.
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Projects that are kernel modules:
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1. Declare a `struct Module`
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2. Contain a `devicetree.yaml` file that declares a list of dependencies (for parsing the devicetree) and specifies the bindings folder that contains the drivers' YAML definitions. For example:
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```yaml
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dependencies:
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- TactilityKernel
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bindings: bindings
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```
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