Re: [PATCH v2] usb: Un-deprecate -usbdevice (except for -usbdevice audio which gets removed)

[Paolo Bonzini]

On Wed, Mar 10, 2021 at 2:17 PM Markus Armbruster <armbru@redhat.com> wrote:
> One more has crept in: "u2f-key" (commit bb014a810, v5.2).  It's buggy:
>
>     $ qemu-system-x86_64 -S -usbdevice u2f-key
>     qemu-system-x86_64: -usbdevice u2f-key: '-usbdevice' is deprecated, 
> please use '-device usb-...' instead
>     **
>     ERROR:../qom/object.c:508:object_initialize_with_type: assertion failed: 
> (type->abstract == false)
>     Bail out! ERROR:../qom/object.c:508:object_initialize_with_type: 
> assertion failed: (type->abstract == false)
>     Aborted (core dumped)
>
> Broken right in the commit that added the stuff.  The sugar never
> worked, and should be taken out again.

Agreed.

> "braille" is the only driver with a factory.  "-usbdevice braille" is
> sugar for
>
>   -device usb-braille,chardev=braille -chardev braille,id=braille
>   -machine usb=on
>
> It's buggy:
>
>     $ qemu-system-x86_64 -S -usbdevice braille
>     qemu-system-x86_64: -usbdevice braille: '-usbdevice' is deprecated, 
> please use '-device usb-...' instead
> [three seconds tick by...]
>     Segmentation fault (core dumped)

Also breaks in the same way with "./qemu-system-x86_64 -S -chardev
braille,id=b", so it's irrelevant.

> It neglects to actually parse PARAMS:
>
>     $ qemu-system-x86_64 -S -usbdevice braille:"I'm a Little Teapot"
>     qemu-system-x86_64: -usbdevice braille:I'm a Little Teapot: '-usbdevice' 
> is deprecated, please use '-device usb-...' instead
> [three seconds tick by...]
>     Segmentation fault (core dumped)
>
> The whole machinery in support of optional PARAMS has long become
> useless.

Agreed. But if parameters and u2f-key are removed, in a separate patch
even, then -usbdevice can be kept as it is in wide use in the wild and
there are no specific issues to be worried about.

Paolo