Re: [Qemu-devel] qemu-doc.texi: Improve USB documentation... and maybe even QEMU also

[Markus Armbruster <armbru@redhat.com>]

Programmingkid <programmingkidx@gmail.com> writes:

> On Aug 24, 2015, at 5:45 AM, Markus Armbruster wrote:
>
>> Copying the USB maintainer.
>> 
>> Programmingkid <programmingkidx@gmail.com> writes:
>> 
>>> On Aug 8, 2015, at 8:48 AM, Programmingkid wrote:
>>> 
>>>> 
>>>> On Aug 8, 2015, at 2:04 AM, Markus Armbruster wrote:
>>>>>> 
>>>>>> USB devices can be connected with the @option{-usbdevice}
>>>>>> commandline option
>>>>>> -or the @code{usb_add} monitor command.  Available devices are:
>>>>>> +or the @code{usb_add} monitor command. Note: some devices may
>>>>>> only work if
>>>>>> +added like this: -usb -device <usb device>. Available devices are:
>>>>> 
>>>>> I'm afraid "may only work" is a bit misleading.  All of them work with
>>>>> -device.  Old ones are also supported by -usbdevice for backward
>>>>> compatibility.  The whole section should be rewritten to point to
>>>>> -device instead of legacy -usbdevice, but that's no reason to hold up
>>>>> your patch.
>>>> 
>>>> I did not know -usbdevice was considered legacy. If that is the
>>>> case, then it should probably
>>>> be removed from the documentation in favor for -usb -device <device name>. 
>>> 
>>> Right now using "-usb -device mouse" doesn't work.
>> 
>> You need to say -device usb-mouse.  See docs/qdev-device-use.txt.  Does
>> it work for you when you do that?
>
> It does. Thank you for this information. 

My pleasure.

>>>                                                   Neither does
>>> "-usbdevice usb-audio".
>> 
>> Yes.  Legacy -usbdevice only supports the devices that predate -device.
>> 
>>> I think we can all agree that consistency among all the USB devices is
>>> a good thing.
>>> Should all USB devices be added like this: -usb -device <device name> ? 
>> 
>> "Should" is perhaps a bit strong.  While -device is the recommended way
>> to add a USB device, -usbdevice is still a supported (if legacy) way to
>> do it.
>> 
>> Of course, "supported, but legacy" interfaces such as -usbdevice may
>> become deprecated, and then you should really move to newer interfaces,
>> because deprecated ones may go away.  Doesn't look terribly probable to
>> me for -usbdevice, though.
>> 
>>> This is an experimental patch of not how QEMU currently works, but how
>>> I think it should work.
>>> 
>>> This documentation adds an "usb_remove" monitor command. This isn't
>>> available right now,
>>> but a patch could be made to change this. Any suggestions or additions
>>> are welcomed.
>> 
>> Why do you think we need usb_remove in addition to device_del?
>
> Ok. usb_remove isn't needed. Why is it that "device_add usb-kbd" works, but
> "device_del usb-kbd" doesn't work? I am given this error message:
> "Device 'usb-kbd' not found".

device_del's argument isn't a driver, it's a device ID.  Try this:

    (qemu) device_add usb-mouse,id=mouse0
    (qemu) info usb
      Device 0.0, Port 1, Speed 12 Mb/s, Product QEMU USB Mouse
    (qemu) device_del mouse0
    (qemu) info usb
    (qemu)