st-u-boot / api /
@Simon Glass Simon Glass authored on 31 Jan 2022
Tom Rini committed on 9 Feb 2022
..
Kconfig Kconfig: Remove all default n/no options 2 years ago
Makefile SPDX: Convert all of our single license tags to Linux Kernel style 6 years ago
README Coding Style cleanup; update CHANGELOG 16 years ago
api.c common: board_r: Drop initr_api wrapper 3 years ago
api_display.c common: Drop log.h from common header 4 years ago
api_net.c SPDX: Convert all of our single license tags to Linux Kernel style 6 years ago
api_platform-arm.c SPDX: Convert all of our single license tags to Linux Kernel style 6 years ago
api_platform-mips.c global: Move from bi_memstart/memsize -> gd->ram_base/ram_size 3 years ago
api_platform-powerpc.c global: Move from bi_memstart/memsize -> gd->ram_base/ram_size 3 years ago
api_private.h common: board_r: Drop initr_api wrapper 3 years ago
api_storage.c scsi: Drop CONFIG_SYS_SCSI_MAX_DEVICE 2 years ago
README
U-Boot machine/arch independent API for external apps
=====================================================

1.  Main assumptions

  - there is a single entry point (syscall) to the API

  - per current design the syscall is a C-callable function in the U-Boot
    text, which might evolve into a real syscall using machine exception trap
    once this initial version proves functional

  - the consumer app is responsible for producing appropriate context (call
    number and arguments)

  - upon entry, the syscall dispatches the call to other (existing) U-Boot
    functional areas like networking or storage operations

  - consumer application will recognize the API is available by searching
    a specified (assumed by convention) range of address space for the
    signature

  - the U-Boot integral part of the API is meant to be thin and non-intrusive,
    leaving as much processing as possible on the consumer application side,
    for example it doesn't keep states, but relies on hints from the app and
    so on

  - optional (CONFIG_API)


2. Calls

  - console related (getc, putc, tstc etc.)
  - system (reset, platform info)
  - time (delay, current)
  - env vars (enumerate all, get, set)
  - devices (enumerate all, open, close, read, write); currently two classes
    of devices are recognized and supported: network and storage (ide, scsi,
    usb etc.)


3. Structure overview

  - core API, integral part of U-Boot, mandatory
    - implements the single entry point (mimics UNIX syscall)

  - glue
    - entry point at the consumer side, allows to make syscall, mandatory
      part

    - helper conveniency wrappers so that consumer app does not have to use
      the syscall directly, but in a more friendly manner (a la libc calls),
      optional part

  - consumer application
    - calls directly, or leverages the provided glue mid-layer