From mboxrd@z Thu Jan  1 00:00:00 1970
Date: Tue, 22 Feb 2011 15:10:12 +0000
To: 9fans@9fans.net
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From: rod@hemiola.co.uk
Subject: [9fans] usb ohci question
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I'm struggling to understand the ins and outs of the usb ohci driver
(usbohci.c) and have a question (well, several).

If one writes to an endpoint, then "epio" gets called. This in turn
does ilock(ctrl) which disables interrupts on my single-processor
machine. Then "epgettd" is called several times to allocate transfer
descriptors. Each call to epgettd copies a portion from the user space
buffer which was passed as a parameter to "epio".

What happens here if the user space buffer is in a page which is not
present? Is it possible for a page-in to happen even when interrupts
are disabled by the ilock?

Thanks for any insight.

rod