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RE: [Qemu-devel] USB storage cannot be recognized on guest Linux domain?


From: Lonnie Mendez
Subject: RE: [Qemu-devel] USB storage cannot be recognized on guest Linux domain?
Date: Thu, 15 Feb 2007 08:48:34 -0600

On Thu, 2007-02-15 at 15:44 +0800, Yu, Xiaoyang wrote:
> Hi Lonnie,
> 
> Thanks a lot for the information.
> 
> In our use case, we do not know the USB disk information before it is plugged 
> by customer, so we cannot start qemu with -usbdevice.
> 
> For Linux, reload the uhci_hcd driver works. If we use this solution in our 
> use case, then we need to issue an interrupt (maybe by pic_set_irq_new?) to 
> the guest OS when QEMU detect a USB device is attached, and then the guest OS 
> will reload the uhci_hcd driver. Is that right? Currently there is something 
> wrong with the list archive server, so I haven't search out any example code 
> from it :-(
> 
> I found that there is a patch to add the UHCI suspend/resume support in the 
> archive posted by you, but it cannot be applied to QEMU-DM 0.8.2 directly:
> http://lists.gnu.org/archive/html/qemu-devel/2006-04/msg00576.html
> 
> I wonder why there is no official UHCI suspend/resume support in QEMU. To 
> reload the uhci_hcd driver seems to be only a work around. Sometimes it even 
> cause kernel oops. 
> 
> I also wonder why the kernel 2.6.11-1.1369_FC4 can recognize USB storage 
> without UHCI suspend/resume support.

The attached patch is enough to have a device on linux recognized after
usb_add.  However, the device must be attached to the uhci controller's
root hub.  If a device is attached to an emulated usb hub device it will
not be detected.

Attachment: qemu-uhci-resume.diff
Description: Text Data


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