tree 0cc7cf63828a47c6153bb7064cc8b19c71d2e069
parent 891781e945318290d657a621dd0ce592c0b43ddd
author Rashmica Gupta <rashmica@linux.ibm.com> 1681280188 +1000
committer Andrew Jeffery <andrew@aj.id.au> 1682050266 +0000

requester: Add new APIs for instance ID allocation and freeing

This patch starts the move of instance id handling into libpldm.
Currently pldmd allocates instance ids, and exposes a DBus call for
external apps to get instance ids. It relies on exploiting a behaviour
of mctp-demux to reclaim used ids by monitoring all incoming PLDM
responses. When moving to AF_MCTP, PLDM messages are not broadcast to
all PLDM sockets, and so this method of reclaiming ids won't work
automatically.

As instance id handling is moving into libpldm eventually, we may as
well do that now rather than adding an additional step to address this
issue. So an allocate and free function for instance ids is added in
this patch.  As this implementation uses file locking, we have the
feature of any ids belonging to a process that dies being automatically
reclaimed into the id pool.

Some context behind the file based range locking design for instance IDs
can be found here:
https://amboar.github.io/notes/2023/03/28/motivating-a-new-scheme-for-pldm-instance-id-management-in-openbmc.html
and
https://amboar.github.io/notes/2023/03/29/a-global-pldm-instance-id-allocator-for-libpldm.html

Change-Id: Ia19870b1bcae9e614bda6e475b290faa0b327a73
Signed-off-by: Rashmica Gupta <rashmica@linux.ibm.com>