| ============== |
| Device Drivers |
| ============== |
| |
| NuttX supports a variety of device drivers, which can be broadly |
| divided in three classes: |
| |
| .. toctree:: |
| :maxdepth: 1 |
| |
| character/index.rst |
| block/index.rst |
| special/index.rst |
| |
| .. note:: |
| Device driver support depends on the *in-memory*, *pseudo* |
| file system that is enabled by default. |
| |
| Lower-half and upper-half |
| ========================= |
| |
| Drivers in NuttX generally work in two distinct layers: |
| |
| * An *upper half* which registers itself to NuttX using |
| a call such as :c:func:`register_driver` or |
| :c:func:`register_blockdriver` and implements the corresponding |
| high-level interface (`read`, `write`, `close`, etc.). |
| implements the interface. This *upper half* calls into |
| the *lower half* via callbacks. |
| * A "lower half" which is typically hardware-specific. This is |
| usually implemented at the architecture or board level. |
| |
