[Xen-devel] wating for backend changes (was Re: [PATCH v3 4/4] libxl: add support for vscsi)

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Olaf Hering writes ("wating for backend changes (was Re: [PATCH v3 4/4] libxl: 
add support for vscsi)"):
> How is new code supposed to wait for backend changes?
> 
> Right now there are two APIs for that:
> - libxl__wait_for_backend loops for a while until it returns an error.

This is deprecated.  I seem to remember I wrote a patch to clarify the
internal docs but it seems to be languishing in one of my outstanding
series.

> - libxl__ev_devstate_wait registers a watch and a timer.

New code should use this.

> In case of pvscsi there are three variants:
> - new, can use libxl__wait_device_connection
> - reconfigure, can use both of the above
> - remove, may use DEFINE_DEVICE_REMOVE and its
>   libxl__initiate_device_remove
...
> The pci code in libxl uses just libxl__wait_for_backend. Looking through
> the history it seems the function was added just for pci. Is it a
> deprecated function, should callers get converted to
> libxl__ev_devstate_wait?

Ideally, yes.

Thanks,
Ian.

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