[Qemu-devel] [Bug 1550743] Re: connect low speed host devices to qemu ehci does not work

[Thomas Huth]

Are you sure that EHCI handles low-speed devices in that case? I thought that 
XHCI is capable of handling low-speed devices instead...
Anyway, QEMU certainly only emulates the EHCI in a traditional way, so if you 
want to use low-speed devices here, you also have to specify an UHCI controller 
for them. I.e. as far as I can see, this is not a bug in QEMU, but just a 
configuration issue.

** Changed in: qemu
       Status: New => Invalid

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https://bugs.launchpad.net/bugs/1550743

Title:
  connect low speed host devices to qemu ehci does not work

Status in QEMU:
  Invalid

Bug description:
  $ qemu-system-i386 -hda my_x86.img -device ich9-usb-ehci1,id=ehci -device 
usb-host,vendorid=0x045e,productid=0x071d -serial stdio
  qemu-system-i386: Warning: speed mismatch trying to attach usb device 
"Microsoft? 2.4GHz Transceiver V" ( speed) to bus "ehci.0", port "1" (high 
speed)
  qemu-system-i386: Warning: speed mismatch trying to attach usb device 
"Microsoft? 2.4GHz Transceiver V" ( speed) to bus "ehci.0", port "1" (high 
speed)
  qemu-system-i386: Warning: speed mismatch trying to attach usb device 
"Microsoft? 2.4GHz Transceiver V" ( speed) to bus "ehci.0", port "1" (high 
speed)

  Which is obviously wrong. The ehci specification states:

  Low-speed device, release ownership of port <= Table 2-16.

  Table 2-6:

  Number of Companion Controller (N_CC). This field indicates the number of
  companion controllers associated with this USB 2.0 host controller.
  A zero in this field indicates there are no companion host controllers. 
Port-ownership
  hand-off is not supported. Only high-speed devices are supported on the host 
controller
  root ports.
  A value larger than zero in this field indicates there are companion USB 1.1 
host
  controller(s). Port-ownership hand-offs are supported. High, Full- and 
Low-speed
  devices are supported on the host controller root ports.

  Which is not longer true, as for example skylake and baytrail offers a
  dual usb stack of ehci and xhci. In that case, EHCI handles the low
  speed device as well.

  brgds,
  Bert

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