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Date:   Fri, 1 Oct 2021 12:45:33 -0400
From:   Alan Stern <stern@rowland.harvard.edu>
To:     Dan Williams <dan.j.williams@intel.com>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Kuppuswamy, Sathyanarayanan" 
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Subject: Re: [PATCH v2 4/6] virtio: Initialize authorized attribute for
 confidential guest
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On Fri, Oct 01, 2021 at 09:13:54AM -0700, Dan Williams wrote:
> Bear with me, and perhaps it's a lack of imagination on my part, but I
> don't see how to get to a globally generic "authorized" sysfs ABI
> given that USB and Thunderbolt want to do bus specific actions on
> authorization toggle events. Certainly a default generic authorized
> attribute can be defined for all the other buses that don't have
> legacy here, but Thunderbolt will still require support for '2' as an
> authorized value, and USB will still want to base probe decisions on
> the authorization state of both the usb_device and the usb_interface.

The USB part isn't really accurate (I can't speak for Thunderbolt). 
When a usb_device is deauthorized, the device will be unconfigured, 
deleting all its interfaces and removing the need for any probe 
decisions about them.  In other words, the probe decision for a 
usb_device or usb_interface depends only on the device's/interface's 
own authorization state.

True, the interface binding code does contain a test of the device's 
authorization setting.  That test is redundant and can be removed.

The actions that USB wants to take on authorization toggle events for 
usb_devices are: for authorize, select and install a configuration; 
for deauthorize, unconfigure the device.  Each of these could be 
handled simply enough just by binding/unbinding the device.  (There 
is some special code for handling wireless USB devices, but wireless 
USB is now defunct.)

Alan Stern