Re: [dpdk-dev] [RFC][PATCH 2/5] pci: allow shared device instances.

[Radu Nicolau <radu.nicolau@intel.com>]

On 5/10/2017 11:28 AM, Thomas Monjalon wrote:
> 10/05/2017 12:11, Radu Nicolau:
>> Hi
>>
>>
>> On 5/10/2017 10:09 AM, Thomas Monjalon wrote:
>>> Hi,
>>>
>>> 09/05/2017 16:57, Radu Nicolau:
>>>> Updated PCI initialization code to allow devices to be shared across multiple PMDs.
>>>>
>>>> Signed-off-by: Radu Nicolau <radu.nicolau@intel.com>
>>> I was waiting the day when we have a device shared
>>> by two different interfaces.
>>> Note that some Mellanox and Chelsio devices already instantiate
>>> two ethdev ports per PCI device.
>>>
>>> Please explain your idea behind this "shared" flag.
>>> What is your exact need?
>> Currently for each pci device a look-up into a list of PMDs is
>> performed, and when a match is found the system moves to the next
>> device. Having this flag will allow a PMD to inform the system that
>> there may be more matches, more PMDs that can be used for this
>> particular device.
>> There is a difference when comparing to the devices you mentioned above,
>> in this case the PMDs are totally different types, one network and one
>> cryptodev PMD for each IXGBE network card.
> Yes I know it is a lack in DPDK.
> Linux introduced MultiFunction Device in 2005:
> 	http://events.linuxfoundation.org/sites/events/files/slides/belloni-mfd-regmap-syscon_0.pdf
>
>>> Do you think it is the best solution?
>> We evaluated different approaches and this is what we settled on. It
>> might not be the best, if there are any suggestions of other ways to
>> achieve this I would be thankful.
> Please could you explain the other approaches you thought
> with pros and cons?
We have considered a vdev crypto PMD approach that would have not 
require changes to the eal section, but it would have required some sort 
of side communication with the IXGBE PMD; another one was a some sort of 
on-demant initialized cryptodev. Over these approaches the current one 
is cleaner and makes more sense, initialize a net and crypto PMD for a 
device that is both a NIC and a cryptro device.

>
> Thanks