[Spice-devel] RFC: spice plans for usb-redir + needed spice-server API extensions

[Hans de Goede]

Hi,

The plan in short:

1) The client decides to redirect a certain usb device
    (be it through user interaction, or based on admin configuration /
     instructed by the controller)

2) The client opens a new usbredir spice channel to the spice-server for
    this (1 channel per device)

3) spice server asks qemu to dynamically create a new spicevmc chardev
    + usb-redir device couple (this is the part that needs the API extension).

4) spice-server forwards requests from the channel to the chardev and
    visa versa

5) On of the first messages send by the client is a usbredir_device_connect
    message, the usb-redir device checks info in this message (usb-id,
    device class) against a configured filter which determines what kind of
    devices can be redirected (if any), and may decide to destroy the usb-device
    before it is ever attached to the guest. The server can notice this
    by spice_server_remove_interface getting called for the chardev.

6) on channel close the usb-redir device is destroyed, this also takes care
    of closing the chardev (which it owns after qdev initalization has
    completed)

Questions:

a) Good plan / bad plan ?

b) since the creation / destruction of the chardev + usb-redir device
    couple is triggered by the spice-server I propose adding the following
    2 new functions to SpiceCoreInterface:

void *(*create_usbredir_device)(void);
void (*destroy_usbredir_device))(void *device);

create_usbredir_device returns either an opaque handle,
or NULL on error; on success qemu_spice_add_interface() will
have been called with a spicevmc chardev interface before this
function returns

destroy_usbredir_device destroys the device in question.

Comments anyone ?

Regards,

Hans