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

[Matthew R. Ochs]

> On May 24, 2016, at 1:59 AM, Vaibhav Jain <vaibhav at linux.vnet.ibm.com> wrote:
> 
> Hi Philippe,
> 
> Few comments,
> 
> Philippe Bergheaud <felix at linux.vnet.ibm.com> writes:
> 
>> diff --git a/drivers/misc/cxl/cxl.h b/drivers/misc/cxl/cxl.h
>> index 4fe5078..b0027e6 100644
>> --- a/drivers/misc/cxl/cxl.h
>> +++ b/drivers/misc/cxl/cxl.h
>> @@ -24,6 +24,7 @@
>> #include <asm/reg.h>
>> #include <misc/cxl-base.h>
>> 
>> +#include <misc/cxl.h>
>> #include <uapi/misc/cxl.h>
>> 
>> extern uint cxl_verbose;
>> @@ -34,7 +35,7 @@ extern uint cxl_verbose;
>>  * Bump version each time a user API change is made, whether it is
>>  * backwards compatible ot not.
>>  */
>> -#define CXL_API_VERSION 2
>> +#define CXL_API_VERSION 3
>> #define CXL_API_VERSION_COMPATIBLE 1
>> 
>> /*
>> @@ -522,6 +523,10 @@ struct cxl_context {
>> 	bool pending_fault;
>> 	bool pending_afu_err;
>> 
>> +	/* Used by AFU drivers for driver specific event delivery */
>> +	struct cxl_afu_driver_ops *afu_driver_ops;
>> +	atomic_t afu_driver_events;
> If the afu_driver_ops.deliver_event is idempotent then instead of using
> a refcount we can simply call afu_driver_ops.deliver_event to see if
> there are any driver events queued. Since callback deliver_event is
> called in context of a spinlock and cannot sleep hence requirement of
> idempotency seems reasonable.

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.