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

  • To: Oleksandr <olekstysh@xxxxxxxxx>
  • From: Jan Beulich <JBeulich@xxxxxxxx>
  • Date: Thu, 1 Aug 2019 15:46:39 +0000
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  • Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
  • Delivery-date: Thu, 01 Aug 2019 15:52:02 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
  • Thread-topic: [Xen-devel] [Question] Proper location for Linux error code (-EPROBE_DEFER) in Xen

On 01.08.2019 16:54, Oleksandr wrote:
> On 01.08.19 17:34, Jan Beulich wrote:
>> On 01.08.2019 16:31, Oleksandr wrote:
>>>    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.
>> I'm sure this can be had without introducing a new error code.
> By reusing existing one (EAGAIN comes to mind)?

For example. Or by using some positive value instead of the (negative)
errno.h ones.

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