如何使用U-Boot API？

Question

I am working with the customized atmel version of U-Boot (u-boot-at91) on an atmel evalboard at91sam9x5ek. I use U-Boot to start Linux which is working fine. I want to implement a simple C application that reads and changes some data from the ram. I was able to compile and run the hello_world example from the examples/standalone/ folder. My problem is that I can't figure out how to access the api-functions made available by glue.h in the examples/api/ folder. I can include the file but get the following error message on compiling:

u-boot-at91/examples/standalone/hello_world.c:34: undefined reference to `ub_env_set'

I added #define CONFIG_API to my boards header file so the api is build.

Answer 1

The function ub_env_set() is implemented in glue.c, here's what it looks like:

void ub_env_set(const char *name, char *value)
{
    syscall(API_ENV_SET, NULL, (uint32_t)name, (uint32_t)value);
}

One option would be to compile and link glue.c into your executable.

Another option would be to just add a copy of ub_env_set() to your code and make sure you're including api_public.h as follows:

#include <api_public.h>

then you should be able to compile.