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Re: [Qemu-devel] [PATCH 0/3] add usb_detach and usb_attach (v3)

From: Anthony Liguori
Subject: Re: [Qemu-devel] [PATCH 0/3] add usb_detach and usb_attach (v3)
Date: Fri, 22 Oct 2010 07:55:02 -0500
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20100915 Lightning/1.0b1 Thunderbird/3.0.8

On 10/22/2010 07:48 AM, Luiz Capitulino wrote:
On Thu, 21 Oct 2010 15:27:23 +0200
Alon Levy<address@hidden>  wrote:

On Thu, Oct 21, 2010 at 08:13:19AM -0500, Anthony Liguori wrote:
On 10/21/2010 08:03 AM, Gerd Hoffmann wrote:
On 10/21/10 08:36, Alon Levy wrote:
v2->v3 changes:
  * add configure parameter
  * fix docs

v2 message:
This patchset uses id like device_del for attaching/detaching usb
devices. The first two patches ready the way:
  1. makes qdev_find_recursive non static and in qdev.h
  2. adds a usb_device_by_id which goes over the usb buses calling
  3. adds the commands that use usb_device_by_id

Alon Levy (3):
   qdev: make qdev_find_recursive public
   usb: add public usb_device_by_id
   monitor: add usb_attach and usb_detach (v2)

Acked-by: Gerd Hoffmann<address@hidden>
Okay, I am still confused about the use-case for this and I don't
see any further explanation in the commit messages.  I've seen
"debugging" but can you be a bit more specific about which cases
it's needed for?
To elaborate a little more, when using a certificates based card
there is no hardware event (i.e. removing/inserting the physical card)
that causes a usb_detach/attach to the card (both in passthru and
emulated), but otoh certificates is good for testing since it decouples
it from NSS/tcp. So I needed some way to emulate an insert/remove, and
I saw usb_del, which was pretty close, and voila. This is not the same
as card remove/reinsert, but it is exactly what will happen to the
guest when spicec connects/disconnects, since I detach devices on
disconnect and attach on connect.
Looks reasonable to me, specially because this will be protected by
#ifdef DEBUG. I don't see a big deal in merging this.

I'd just like to see better documentation. A command isn't useful for debugging if noone knows how to use it.

Guarding with an #ifdef isn't necessary. It should be unconditionally enabled otherwise it will bit rot.

Objections, Anthony?

Not with better docs.


Anthony Liguori

This is just adding a HMP command.  Is that the right approach or
was that an unintentional consequence of rebasing post-HMP/QMP
I don't think this should be available under QMP, it's more a debugging
command for USB developers.


Anthony Liguori


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