Re: plans for user-backed device support
by Andy Grover
On 02/04/2015 12:21 PM, Alex Elsayed wrote:
>> Maybe we step back and define a DBus interface
>
> I'd be quite happy with that - I considered suggesting it, in fact, but
> wasn't sure of the prevailing opinion re: dbus around here.
>
> What would you do re: discovery, though?
>
> (Explaining some DBus things, which readers may already be aware of)
>
> In DBus, there's a two-level hierarchy of busnames holding objects.
> Busnames are either the inherent, connection-level one of the :\d+.\d+ form,
> or the human-readable well-known name form (reverse DNS). Objects, then,
> implement interfaces.
>
> However, well-known names can only have a single owner - so discovering
> which busnames have objects which implement an interface is non-trivial.
>
> The approach taken by KDE is to suffix the well-known name with the PID
> (org.kde.StatusNotifierItem-2055 or whatever), call ListNames, and filter in
> the client. This has the drawback of making DBus activation impossible.
>
> Another approach is for every implementor to try to claim the well-known
> name, and on failure contact the existing owner to republish their objects
> (possibly under a namespaced object path). This has the drawback of
> complicating the implementation somewhat, as well as making bus activation
> only able to activate a single 'default' implementation.
>
> A third approach would be to explicitly define a multiplexor, which backends
> ask to republish their objects. This simplifies implementations, and it
> could also provide its own API that requests a backend by name, and ensures
> that backend's object is available. This could be driven by something as
> simple as a key-value mapping from backend name to a well-known DBus name
> specific to that backend, which the multiplexor calls to trigger service
> activation.
>
> Thoughts?
It really seems to come down to: will multiple independent user-handler
daemons be needed? Because I'm trying really hard to make tcmu-runner
good enough so that the answer is no :-)
tcmu-runner supports multiple handler modules, so it's extensible. It is
permissively licensed so no issues with non-FOSS handlers needing their
own daemon. It also could be replaced entirely (either with a modified
version of itself or from scratch) and still not give up the
single-busname, service activation approach.
So that would be my current preference. (The fact that the kernel API
doesn't preclude multiple handler daemons does not mean we need to
*support* those right away, or ever.)
If there are likely use cases that tcmu-runner is unsuitable for solving
by itself then that would change things of course, and let's please talk
about them!
-- Andy
8 years, 6 months
LIO in 4.2.[12] broken?
by Leeman Strout
I recently upgraded my kernel to 4.2.1, then due to issues with iSCSI
jumped to 4.2.2 in case that fixed things. Well it didn't so I'm back
to 4.1.6.
I am running the _fb series of tools/API and was hoping to hear from
anyone on the list that has tried the 4.2 kernel series and might have
any insight.
These are the errors I got when trying to connect via the Windows 8
iSCSI initiator:
Got unknown iSCSI OpCode: 0x43
Cannot recover from unknown opcode while ERL=0, closing iSCSI connection.
Thanks,
Leeman
8 years, 6 months
