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From: rod@hemiola.co.uk
To: 9fans@9fans.net
Subject: [9fans] usb ohci - one more question
Date: Tue, 22 Feb 2011 17:02:42 +0000	[thread overview]
Message-ID: <20110222170448.9473A65D3E@server.hemiola.co.uk> (raw)

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



             reply	other threads:[~2011-02-22 17:02 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-02-22 17:02 rod [this message]
2011-02-22 17:17 ` Francisco J Ballesteros
2011-02-22 17:29   ` Richard Miller
2011-02-22 17:39     ` rod
2011-02-22 18:56       ` Francisco J Ballesteros

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