README
1U-Boot machine/arch independent API for external apps
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41. Main assumptions
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6 - there is a single entry point (syscall) to the API
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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
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12 - the consumer app is responsible for producing appropriate context (call
13 number and arguments)
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15 - upon entry, the syscall dispatches the call to other (existing) U-Boot
16 functional areas like networking or storage operations
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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
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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
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27 - optional (CONFIG_API)
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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.)
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413. Structure overview
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43 - core API, integral part of U-Boot, mandatory
44 - implements the single entry point (mimics UNIX syscall)
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46 - glue
47 - entry point at the consumer side, allows to make syscall, mandatory
48 part
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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
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54 - consumer application
55 - calls directly, or leverages the provided glue mid-layer
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