Re: [Xen-devel] [Question] Proper location for Linux error code (-EPROBE_DEFER) in Xen

[Oleksandr <olekstysh@xxxxxxxxx>]

> Hello,
Hi, Roger


> I think it would help if you describe why such error code is needed by
> Xen and how it would be used.
 This is needed for the upcoming V2 of the IPMMU driver (ARM) [1] which 
may request
 deferred probing (returns -EPROBE_DEFER) depending on what device will 
be probed the first
 (Root device must be registered before Cache devices. If not the case,
 driver will deny further Cache device probes until Root device is 
registered).
As we can't guarantee a fixed pre-defined order for the device nodes in 
DT, we need to be ready for the situation where devices being probed
in "any" order. So, framework (drivers/passthrough/arm/iommu.c) will be 
modified a bit to be able to handle -EPROBE_DEFER returning by driver.
[1] 
https://lists.xenproject.org/archives/html/xen-devel/2017-07/msg02679.html

--
Regards,

Oleksandr Tyshchenko


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