[v5, 1/2] cxl: Add mechanism for delivering AFU driver specific events

[Vaibhav Jain]

Hi Matt,

"Matthew R. Ochs" <mrochs at linux.vnet.ibm.com> writes:
> The purpose for the count is so the AFU driver is only called when it
> has something to send. Otherwise we don't want to be called.

Agreed, but this opens up a possible boundary condition where in we have
non-zero event count and deliver_event callback returns a NULL/empty
struct (This isn't handled correctly at the moment). Imo the condition
event-count == number-of-calls-to-deliver_events is bit too rigid.

Instead a more relaxed condition can be number-of-calls-to-deliver_event ==
count-until-deliver_event-returns-NULL. This could be implemented as
boolean flag inside the context to indicate that afu-driver has some
events queued. This flag can be set when cxl_context_events_pending gets
called. The cxl code can simply call deliver_event on each read call
untill it returns NULL in which case this boolean flag is reset.

This should slightly simplify the code flow at the afu-driver end as
enquing to an event need not be paired by a call to
cxl_context_events_pending. It can quite possibly enqueue bunch of
events and then do a single call to cxl_context_events_pending. In this
case the function cxl_context_events_pending essentially works more like
a function named as cxl_context_events_flush.

~ Vaibhav