Virtio-blk extended lifetime feature

[Alvaro Karsz]

Hi guys,

While trying to upstream the implementation of VIRTIO_BLK_F_LIFETIME
feature, many developers suggested that this feature should be
extended to include more cell types, since its current implementation
in virtio spec is relevant for MMC and UFS devices only.

The VIRTIO_BLK_F_LIFETIME defines the following fields:

- pre_eol_info:  the percentage of reserved blocks that are consumed.
- device_lifetime_est_typ_a: wear of SLC cells.
- device_lifetime_est_typ_b: wear of MLC cells.

(https://docs.oasis-open.org/virtio/virtio/v1.2/virtio-v1.2.html)

Following Michael's suggestion, I'd like to add to the virtio spec
with a new, extended lifetime command.
Since I'm more familiar with embedded type storage devices, I'd like
to ask you guys what fields you think should be included in the
extended command.

Thanks,

Alvaro