Re: [Qemu-devel] [PATCH 14/14] usb-host: add timeout handler

[Gerd Hoffmann]

  Hi,

> When the "end" packet is received the actual flashing starts,
> which can take minutes.  The device will not ACK the packet
> until flashing completes.  Thus I now get an error from the
> flash tool (while flashing completes on the device).
> Qemu says:
> 
>   husb: urb timeout (5 secs, #1)
> 
> I think 5 seconds default timeout may also cause issues
> with slow devices (hard disk spinning up, CDROM reading
> disc TOC etc.).  It seems unneccessary since the guest OS
> handles timeouts specified by drivers/applications
> on URB submission, and will cancel transfers on timeout.
> Has this been added to fix an actual problem?

Has been added to detect requests getting stuck.  I'm seeing this now
and then with linux guests polling usb sticks (test unit ready every few
seconds).  Seems to be a bug somewhere, not root-caused yet.

/me wanted qemu handle it and warn about this (like it warns already in
case device reset takes unusual long).  But, yes, I can see how this can
cause more harm than it helps as usb-host has no way to figure how long
a certain operation will take.

Pushed usb.49 with this patch dropped.

cheers,
  Gerd