Re: [PATCH v2 0/2] Simplify mtty driver and mdev core

From: Cornelia Huck
Date: Tue Aug 20 2019 - 13:55:35 EST

On Tue, 20 Aug 2019 11:19:04 -0600
Alex Williamson <alex.williamson@xxxxxxxxxx> wrote:

> What about an alias based on the uuid? For example, we use 160-bit
> sha1s daily with git (uuids are only 128-bit), but we generally don't
> reference git commits with the full 20 character string. Generally 12
> characters is recommended to avoid ambiguity. Could mdev automatically
> create an abbreviated sha1 alias for the device? If so, how many
> characters should we use and what do we do on collision? The colliding
> device could add enough alias characters to disambiguate (we likely
> couldn't re-alias the existing device to disambiguate, but I'm not sure
> it matters, userspace has sysfs to associate aliases). Ex.
> UUID=$(uuidgen)
> ALIAS=$(echo $UUID | sha1sum | colrm 13)
> Since there seems to be some prefix overhead, as I ask about above in
> how many characters we actually have to work with in IFNAMESZ, maybe we
> start with 8 characters (matching your "index" namespace) and expand as
> necessary for disambiguation. If we can eliminate overhead in
> IFNAMESZ, let's start with 12. Thanks,
> Alex

I really like that idea, and it seems the best option proposed yet, as
we don't need to create a secondary identifier.