Re: [PATCH] hw/usb: Introduce x-query-usbhost QMP command

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 10/6/24 10:33, Daniel P. Berrangé wrote:
> On Mon, Jun 10, 2024 at 08:38:47AM +0200, Philippe Mathieu-Daudé wrote:
>> This is a counterpart to the HMP "info usbhost" command. It is being
>> added with an "x-" prefix because this QMP command is intended as an
>> adhoc debugging tool and will thus not be modelled in QAPI as fully
>> structured data, nor will it have long term guaranteed stability.
>> The existing HMP command is rewritten to call the QMP command.
> 
> 'info usb' host is one of the problem scenarios i mentioned in
> 
> https://lore.kernel.org/qemu-devel/20211028155457.967291-1-berrange@redhat.com/
> 
> Its HMP impl is within a dynamically loadable module. So if you
> run it initially you'll get
> 
> (qemu) info usbhost
> Command "info usbhost" is not available.
> 
> 
> but if you have a usb host on the cli:
> 
> (qemu) info usbhost
>    Bus 3, Addr 6, Port 8, Speed 480 Mb/s
>      Class ef: USB device 04f2:b74f
>    Bus 3, Addr 11, Port 7.3, Speed 1.5 Mb/s
>    ...snip...
> 
> 
> Anyway, the end result is that this patch fails to link when modules
> are enabled:
> 
> cc -m64 @qemu-system-x86_64.rsp
> /usr/bin/ld: libqemuutil.a.p/meson-generated_.._qapi_qapi-commands-machine.c.o: in function `qmp_marshal_x_query_usbhost':
> /var/home/berrange/src/virt/qemu/build/qapi/qapi-commands-machine.c:1514: undefined reference to `qmp_x_query_usbhost'

Indeed I missed that.

> IMHO the solution to this is to refactor the cdoe to split
> hw/usb/host-libusb.c into two parts.
> 
> One part provides the monitor API impls, and some callbacks
> for feeding data to them. The other part provides the actual
> impl, and registers the callbacks needed by the monitor cmd.

Yeah something like that will do.