driver questions

[Christopher Biessener]

I have searched using google for information regarding linux driver 
development and have found a lot, but not the answers to these questions:
* Can 2 different kernel drivers access the same device at the same time?
* Is every driver known as a kernel module?

Basically I need advice on if I can and how to sidestep some of the 
libata device calls.  We do not want to replace the entire libata, just 
some of it.  We have a custom piece of hardware that writes to hard 
drives.  When we use another one of our devices to act as the host the 
client device runs at full speed.  When we run the python GUI with our 
custom C++ extension using only SATA ports on the motherboard the 
program runs at full speed.  But when we use the python GUI to drive our 
custom hardware we lose 40% of the speed.  We believe the speed loss to 
be in how libata optimizes how it sends commands/data to the hard 
drive/device.

Thanks in advance,

Christopher