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

[Alon Levy]

On Fri, Oct 22, 2010 at 07:55:02AM -0500, Anthony Liguori wrote:
> 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
> >>>>>   qdev_find_recursive
> >>>>>  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.
> 

ok, so no QMP and better docs. Where should the docs go? just have
more descriptive help messages? or in docs/usb_attach_detach.txt (for
example)?

> Regards,
> 
> 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
> >>>split?
> >I don't think this should be available under QMP, it's more a debugging
> >command for USB developers.
> >
> >>>Regards,
> >>>
> >>>Anthony Liguori
> >>>
> >>>>cheers,
> >>>>  Gerd
> >>>>
> >>>>
> >>>
>