u-boot

mirror of https://github.com/u-boot/u-boot.git synced 2024-11-27 14:14:37 +08:00

History

Masahiro Yamada ad420282e2 Makefile: descend into subdirectories only when CONFIG_API is defined All objects under api/ and examples/api/ directories are selected by CONFIG_API. So we can move CONFIG_API switch to the top Makefile. In order to use CONFIG_API, the definition of SUBDIR_EXAMPLES-y must be moved after "sinlude $(obj)include/autoconf.mk". Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>		2013-11-25 10:41:54 -05:00
..
api_display.c	Add GPL-2.0+ SPDX-License-Identifier to source files	2013-07-24 09:44:38 -04:00
api_net.c	Add GPL-2.0+ SPDX-License-Identifier to source files	2013-07-24 09:44:38 -04:00
api_platform-arm.c	Add GPL-2.0+ SPDX-License-Identifier to source files	2013-07-24 09:44:38 -04:00
api_platform-powerpc.c	Add GPL-2.0+ SPDX-License-Identifier to source files	2013-07-24 09:44:38 -04:00
api_private.h	Add GPL-2.0+ SPDX-License-Identifier to source files	2013-07-24 09:44:38 -04:00
api_storage.c	Add GPL-2.0+ SPDX-License-Identifier to source files	2013-07-24 09:44:38 -04:00
api.c	Add GPL-2.0+ SPDX-License-Identifier to source files	2013-07-24 09:44:38 -04:00
Makefile	Makefile: descend into subdirectories only when CONFIG_API is defined	2013-11-25 10:41:54 -05:00
README	Coding Style cleanup; update CHANGELOG	2008-01-10 00:55:14 +01:00

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