Queue/Buffer size

Hi all,
I have had a look through the source code, and it seems that the queue 
length/buffer size (TX) is set to 200 packets. Can someone confirm that 
it is packets/frame?

As per if_athvar.h file,

#define ATH_TXBUFF 200

How is then the txqueuelen in Linux associated with this value? Or is 
this the driver or the interface queue? Does the following still apply?

Interface TX queue --> Driver --> Driver TX queue

I am just trying to understand how the queueing works.

Regards,
Kewin

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