This is in preparation to switch qemu-server from using '-drive' to
the modern '-blockdev' in the QEMU commandline options as well as for
the qemu-storage-daemon, which only supports '-blockdev'. The plugins
know best what driver and options are needed to access an image, so
a dedicated plugin method returning the necessary parameters for
'-blockdev' is the most straight-forward.
There intentionally is only handling for absolute paths in the default
plugin implementation. Any plugin requiring more needs to implement
the method itself. With PVE 9 being a major release and most popular
plugins not using special protocols like 'rbd://', this seems
acceptable.
For NBD, etc. qemu-server should construct the blockdev object.
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
073c5677c7