wait_queue_head_t vs. wait_queue_t

[Timur Tabi]

Could someone explain to me the difference between wait_queue_head_t and
wait_queue_t?  I'm trying to port some code from 2.2 to 2.4, and I'm getting
these two structures confused.  What makes it worse is that the drivers in the
2.4 kernel which use these structures don't seem to explain their usage it.
For instance, I see this code a lot (from
/usr/src/linux-2.4.0-test2/drivers/usb/serial/digi_acceleport.c):

	wait_queue_t wait;

	init_waitqueue_entry( &wait, current );

	add_wait_queue( q, &wait );

	...

	remove_wait_queue( q, &wait );

Why doesn't the code initialize the "struct list_head task_list" element in
wait_queue_t? 

-- 
Timur Tabi - [e-mail]
Interactive Silicon - http://www.interactivesi.com

When replying to a mailing-list message, please don't cc: me, because then I'll
just get two copies of the same message.