[U-Boot-Users] Why are some global vars part of the image, and some not?

[Timur Tabi]

I have the following code in one of my files:

#ifdef CFG_SPD_BUS_NUM
static volatile unsigned int i2c_bus_num = CFG_SPD_BUS_NUM;
#else
static volatile unsigned int i2c_bus_num = 0;
#endif

static volatile struct fsl_i2c *i2c_dev[2] = {
	(struct fsl_i2c *) (CFG_IMMR + CFG_I2C_OFFSET),
#ifdef CFG_I2C2_OFFSET
	(struct fsl_i2c *) (CFG_IMMR + CFG_I2C2_OFFSET)
#endif
};

As you can see, I defined two static volatile global vars: i2c_bus_num and 
i2c_dev.

My U-Boot image is 0x294E0 bytes in size, and it's located at address 
0xFE000000.  When I run U-Boot, the address of i2c_bus_num is 0xfe02a114, and 
the address of i2c_dev[] is 0xfe028124.

In other words, i2c_dev[] is part of the actual U-Boot image, but i2c_bus_num, 
which is defined right next to it, isn't.  This means that i2c_dev[] is 
properly initialized, but i2c_bus_num is set to 0xFFFFFFFF (the value that 
erased flash has).

How is this possible?  How can two adjacent global variables be located is 
completely different memory segments?

-- 
Timur Tabi
Linux Kernel Developer @ Freescale