From mboxrd@z Thu Jan  1 00:00:00 1970
Date: Tue, 22 Feb 2011 17:02:42 +0000
To: 9fans@9fans.net
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From: rod@hemiola.co.uk
Subject: [9fans] usb ohci - one more question
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May I have one more question?

When you create a new bulk or interrupt endpoint "epopen" is called.
The aux field of the Ep is set to point to an array of two Qio
structures. One for input and one for output. Both of those in turn
have a pointer to, and a one-to-one correspondence with, an endpoint
descriptor (Ed). "newed" is called for each Qio to link the Qio's
endpoint descriptor into the controller's chain.

I can't figure out why there are two Qio structs. The usb spec says
that bulk/interrupt endpoints are unidirectional, so why wouldn't just
a single one do?

Thanks,

rod