Re: [PATCH libibverbs] Fix create/destroy flow API

[Doug Ledford <dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

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On 09/04/2015 05:32 PM, Jason Gunthorpe wrote:
> On Fri, Sep 04, 2015 at 05:17:38PM -0400, Doug Ledford wrote:
>> +		/*
>> +		 * In order to maintain backward/forward binary compatibility
>> +		 * with libmlx4-1.0.6, which has the original version of the
>> +		 * flow steering patches, we need to set the two
>> +		 * ABI_compat_placeholder entries to match the driver
>> +		 * set flow entries.  This is because, in the specific instance
>> +		 * of using libmlx4-1.0.6 with the fixed version of
>> +		 * libibvberbs, the ibv_create_flow inline function already
>> +		 * compiled into libmlx4-1.0.6 will be loooking in the
>> +		 * ABI_placeholder spots for the function pointer to the
>> +		 * create and destroy flow verbs.
>>  		 */
> 
> This isn't quite the right comment, it has very little to do with mlx,
> ibv_create_flow is the user entry point, the above applies to
> everything linked to ibverbs.

You're right.  I'll correct that.

> My suggestion was to not change the ibverbs->user ABI at all and just
> mangle the driver side, ie move the ABI_placeholder to what was drv_
> instead of lib_.

As you pointed out, this doesn't make the entire matrix of old/new
driver/libibverbs/app work.  I can think of two things that would be
ugly about doing it this way if we wanted to make that matrix fully
operational.  With the way I did it, things are clean in the new driver
and mostly clean in the new libibverbs, and the full matrix works.

> Can't see anything wrong with it this way, off hand, other than the
> comment.

Thanks for looking at it ;-)

-- 
Doug Ledford <dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
              GPG KeyID: 0E572FDD



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