[ironic] On redfish-virtual-media vs idrac-redfish-virtual-media
dtantsur at redhat.com
Wed Jan 20 17:54:15 UTC 2021
Now that we've gained some experience with using Redfish virtual media I'd
like to reopen the discussion about $subj. For the context, the
idrac-redfish-virtual-media boot interface appeared because Dell machines
need an additional action  to boot from virtual media. The initial
position on hardware interfaces was that anything requiring OEM actions
must go into a vendor hardware interface. I would like to propose relaxing
this (likely unwritten) rule.
You see, this distinction causes a lot of confusion. Ironic supports
Redfish, ironic supports iDRAC, iDRAC supports Redfish, ironic supports
virtual media, Redfish supports virtual media, iDRAC supports virtual
media. BUT! You cannot use redfish-virtual-media with iDRAC. Just today I
had to explain the cause of it to a few people. It required diving into how
exactly Redfish works and how exactly ironic uses it, which is something we
want to protect our users from.
We already have a precedent  of adding vendor-specific handling to a
generic driver. I have proposed a patch  to block using
redfish-virtual-media for Dell hardware, but I grew to dislike this
approach. It does not have precedents in the ironic code base and it won't
scale well if we have to handle vendor differences for vendors that don't
have ironic drivers.
Based on all this I suggest relaxing the rule to the following: if a
feature supported by a generic hardware interface requires additional
actions or has a minor deviation from the standard, allow handling it in
the generic hardware interface. Meaning, redfish-virtual-media starts
handling the Dell case by checking the System manufacturer (via the
recently added detect_vendor call) and loading the OEM code if it matches
"Dell". After this idrac-redfish-virtual-media will stay empty (for future
enhancements and to make the patch backportable).
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