Long story short I have a custom board for personal use that is essentially 
a cape for the BBB. It has a 24c256 EEPROM on I2C-2, just like the example 
in the reference manual 
<https://github.com/beagleboard/beaglebone-black/wiki/System-Reference-Manual#821-eeprom-address>
. 

I'm having severe difficulty interpreting these lines though:

> Address line A2 is always tied high. This sets the allowable address range 
> for the expansion cards to 0x54 to 0x57. All other I2C addresses can be 
> used by the user in the design of their capes.


When I boot the BBB and run i2cdetect on i2c-2, I can see that addresses 
0x54-0x57 are reserved by the kernel, because they're shown as "UU" in the 
i2cdetect output. This means I can't read/write to this chip if I want to, 
as I don't have permission from userland.

So from what I can tell with all of this, and please correct me if I'm 
being an idiot, is that you want to use addresses 0x54-0x57 to store read 
only pinmux data for your cape, and the kernel can pick this up and adapt 
according via device trees or whatever. If you want a readable/writeable 
EEPROM for other information you would have to tie A2 to ground, and thus 
move the address out of the kernel reserved space, making it something 
between 0x50-0x53. Is this correct, or am I just horrible misinterpreting 
the reference manual?

Any pointers would be great at this point, I just want to make sure I 
really understand the reason those addresses are reserved by the kernel, 
and what an eeprom with those addresses is actually used for. Thanks.

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