From 500856eb1707ed17d9204baa61dd59948d3b2899 Mon Sep 17 00:00:00 2001 From: Rafal Jaworowski Date: Wed, 9 Jan 2008 19:39:36 +0100 Subject: API for external applications. This is an API for external (standalone) applications running on top of U-Boot, and is meant to be more extensible and robust than the existing jumptable mechanism. It is similar to UNIX syscall approach. See api/README for more details. Included is the demo application using this new framework (api_examples). Please note this is still an experimental feature, and is turned off by default. Signed-off-by: Rafal Jaworowski --- api/README | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 55 insertions(+) create mode 100644 api/README (limited to 'api/README') diff --git a/api/README b/api/README new file mode 100644 index 0000000000..c8f9c457c4 --- /dev/null +++ b/api/README @@ -0,0 +1,55 @@ +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 -- cgit v1.2.3