Re: [Qemu-devel] [PATCH 0/4] usb/hid: bugfixes, more on usb and hid split

[Gerd Hoffmann <kraxel@redhat.com>]

On 08/07/11 19:29, Michael Walle wrote:
> This USB patchset moves the VM state stuff from usb-hid.c to hid.c, so it
> can be reused by other devices.

Nice.

> There is one major drawback: i need to increase the vmstate version_id of
> the usb-hid device. I don't know if you agree with this change.
> Alternatively, we could add a load_old function which just skips old
> versions.

You don't have to change the version.  The binary representation in the 
savevm format doesn't change if you move the fields from vmstate_usb_ptr 
to vmstate_hid_ptr_device.

For anything referenced via VMS_STRUCT the vmstate->name is just there 
to beautify the source code, it isn't used at all when reading/writing 
the state.  No new section, no nothing.  The savevm code only looks at 
->fields and writes them out (and executes the hooks).

Reordering the fields (like you did with the keyboard) isn't going to 
work though.

cheers,
   Gerd