Re: [PATCH v4 3/7] bbdev: add device info on queue topology

[Tom Rix <trix@redhat.com>]

On 7/6/22 2:12 PM, Chautru, Nicolas wrote:
> Hi Tom,
>
>> -----Original Message-----
>> From: Tom Rix <trix@redhat.com>
>> Subject: Re: [PATCH v4 3/7] bbdev: add device info on queue topology
>>
>>
>> On 7/5/22 5:23 PM, Nicolas Chautru wrote:
>>> Adding more options in the API to expose the number of queues exposed
>>> and related priority.
>>>
>>> Signed-off-by: Nicolas Chautru <nicolas.chautru@intel.com>
>>> ---
>>>    lib/bbdev/rte_bbdev.h | 4 ++++
>>>    1 file changed, 4 insertions(+)
>>>
>>> diff --git a/lib/bbdev/rte_bbdev.h b/lib/bbdev/rte_bbdev.h index
>>> 9b1ffa4..ac941d6 100644
>>> --- a/lib/bbdev/rte_bbdev.h
>>> +++ b/lib/bbdev/rte_bbdev.h
>>> @@ -289,6 +289,10 @@ struct rte_bbdev_driver_info {
>>>
>>>    	/** Maximum number of queues supported by the device */
>>>    	unsigned int max_num_queues;
>>> +	/** Maximum number of queues supported per operation type */
>>> +	unsigned int num_queues[RTE_BBDEV_OP_TYPE_PADDED_MAX];
>>> +	/** Priority level supported per operation type */
>>> +	unsigned int queue_priority[RTE_BBDEV_OP_TYPE_PADDED_MAX];
>> It is better to add new elements to the end of a structure for better backward
>> compatibility
> All that serie is not ABI compatible (sizes change etc...). I don’t believe there is such a recommendation, is there?

Depends on what users expect, a dynamically linked old application would 
at best core here.  If the elements were added to the end, yes the size 
would change but the old dynamically linked application would not use 
them.  Dynamically linking is nice because problems in the library can 
be fixed and shipped without forcing the user recompile.  Though the 
user may not realize  it, this change forces them to recompile.

Tom

>
>> Tom
>>
>>>    	/** Queue size limit (queue size must also be power of 2) */
>>>    	uint32_t queue_size_lim;
>>>    	/** Set if device off-loads operation to hardware  */