source: SVN/rincon/u-boot/api/README @ 55

Last change on this file since 55 was 55, checked in by Tim Harvey, 22 months ago

rincon: added latest u-boot source

restored form server backup

Signed-off-by: Tim Harvey <tharvey@…>

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1U-Boot machine/arch independent API for external apps
2=====================================================
3
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)
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29
302. Calls
31
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.)
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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
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