uboot/api/README
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   1U-Boot machine/arch independent API for external apps
   2=====================================================
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   41.  Main assumptions
   5
   6  - there is a single entry point (syscall) to the API
   7
   8  - per current design the syscall is a C-callable function in the U-Boot
   9    text, which might evolve into a real syscall using machine exception trap
  10    once this initial version proves functional
  11
  12  - the consumer app is responsible for producing appropriate context (call
  13    number and arguments)
  14
  15  - upon entry, the syscall dispatches the call to other (existing) U-Boot
  16    functional areas like networking or storage operations
  17
  18  - consumer application will recognize the API is available by searching
  19    a specified (assumed by convention) range of address space for the
  20    signature
  21
  22  - the U-Boot integral part of the API is meant to be thin and non-intrusive,
  23    leaving as much processing as possible on the consumer application side,
  24    for example it doesn't keep states, but relies on hints from the app and
  25    so on
  26
  27  - optional (CONFIG_API)
  28
  29
  302. Calls
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  32  - console related (getc, putc, tstc etc.)
  33  - system (reset, platform info)
  34  - time (delay, current)
  35  - env vars (enumerate all, get, set)
  36  - devices (enumerate all, open, close, read, write); currently two classes
  37    of devices are recognized and supported: network and storage (ide, scsi,
  38    usb etc.)
  39
  40
  413. Structure overview
  42
  43  - core API, integral part of U-Boot, mandatory
  44    - implements the single entry point (mimics UNIX syscall)
  45
  46  - glue
  47    - entry point at the consumer side, allows to make syscall, mandatory
  48      part
  49
  50    - helper conveniency wrappers so that consumer app does not have to use
  51      the syscall directly, but in a more friendly manner (a la libc calls),
  52      optional part
  53
  54  - consumer application
  55    - calls directly, or leverages the provided glue mid-layer
  56