module loading order

[simonleung@gmx.com (Simon Leung)]

Hi all,

This is a question that arose from a older kernel ( 2.6.21 ) but I think 
it's generic to all kernels. Actually this might not a question on the 
kernel itself at all. So here it goes,

I'm using a USB 3G modem with this kernel. The system loads three 
modules for it: pl2303, option and usbserial. Problem is, it looks like 
the order or loading is different ( I'm judging this by the order they 
appear in lsmod output):

Sometimes, lsmod says:
pl2303                 18628  0
option                  9664  0
usbserial              28296  2 pl2303,option

And sometimes, it says:
option                  9664  0
pl2303                 18628  0
usbserial              28296  2 option,pl2303

Problem is, if option is before pl2303, the device won't work properly. 
So my question is: who decides which is loaded first, or, why does lsmod 
give different order?

Thanks a lot!