Subject: Re: sudden detach
To: None <tech-kern@NetBSD.org>
From: Garrett D'Amore <firstname.lastname@example.org>
Date: 07/11/2006 13:02:32
David Young wrote:
> On Tue, Jul 04, 2006 at 03:23:02PM +0200, Jachym Holecek wrote:
>> If we can agree to require user intervention before removing hotplug
>> devices (which is what Windows XP does, not sure about other systems),
>> then we "should" get rid of ca_activate (as we know it now, anyway).
>> There was a short thread on this recently, the argument for keeping
>> them was exactly "we need a quick deactivation from hardintr when
>> we get a device-gone interrupt".
> I have always considered it a bug in Windows XP that the user has to
> intervene before a device can be removed. I thought that both USB and
> Cardbus were designed to make a sudden detach possible? In principle,
> can't a carefully written driver survive a sudden detach?
In principle this is true for USB, and it _may_ be true for Cardbus.
But the reality is that cardbus drivers generally share code with PCI
(for most OS' they use the same driver entirely, although for some
reason NetBSD has a separate Cardbus support apart from PCI) and those
drivers are generally _not_ hotplug safe.
A major point of Cardbus is to make it possible to use vanilla PCI code
with cardbus. Such code cannot generally cope in event of random device
Garrett D'Amore, Principal Software Engineer
Tadpole Computer / Computing Technologies Division,
General Dynamics C4 Systems
Phone: 951 325-2134 Fax: 951 325-2191