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u-boot/api
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Stanislav Galabov 22aa61f707 api: Export API structure address as an environment variable 
This patch makes the U-Boot api export its structure address as an environment
variable, so it can be used to directly hint FreeBSD's loader of api's location.

The relevant FreeBSD loader change is currently under review at:
https://reviews.freebsd.org/D5492

Signed-off-by: Stanislav Galabov <sgalabov@gmail.com>
2016-03-08 15:01:45 -05:00
..
api.c api: Export API structure address as an environment variable 2016-03-08 15:01:45 -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 net: Remove the bd* parameter from net stack functions 2015-04-18 11:11:11 -06:00
api_platform-arm.c Add GPL-2.0+ SPDX-License-Identifier to source files 2013-07-24 09:44:38 -04:00
api_platform-mips.c api: Add FreeBSD API support for MIPS platforms 2016-02-08 10:22:38 -05:00
api_platform-powerpc.c powerpc: mpc8260: consolidate CONFIG_MPC8260 and CONFIG_8260 2014-03-07 10:59:06 -05:00
api_private.h Add GPL-2.0+ SPDX-License-Identifier to source files 2013-07-24 09:44:38 -04:00
api_storage.c block: pass block dev not num to read/write/erase() 2016-01-13 21:05:18 -05:00
Makefile api: Add FreeBSD API support for MIPS platforms 2016-02-08 10:22:38 -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