Re: [dpdk-dev] DPDK and HW offloads

["Qiu, Michael" <michael.qiu@intel.com>]

On 3/21/2016 11:27 PM, Kyle Larose wrote:
> On Mon, Mar 21, 2016 at 10:52 AM, Bruce Richardson
> <bruce.richardson@intel.com> wrote:
>> On Sun, Mar 20, 2016 at 08:18:57PM +0100, Thomas Monjalon wrote:
>>> 2016-03-20 14:17, Zhang, Helin:
>>>> From: Thomas Monjalon [mailto:thomas.monjalon@6wind.com]
>>>>> 2016-03-18 10:16, Stephen Hemminger:
>>>>>> Right now, all those offload features are pretty much unusable in a
>>>>>> real product without lots and lots of extra codes and huge bug
>>>>>> surface. It bothers me enough that I would recommend removing much of the
>>>>> filter/offload/ptype stuff from DPDK!
>>>>>
>>>>> One of the biggest challenge is to think about a good filtering API.
>>>>> The offloading has some interaction with the mbuf struct.
>>>>>
>>>>> I would like to suggest rewriting ethdev API by keeping it as is for some time for
>>>>> compatibility while creating a new one. What about the prefix dpdk_netdev_ to
>>>>> progressively replace rte_eth_dev?
>>>> I totally agree with to add new and generic APIs for user applications. But I don't
>>>> think we need to remove all current APIs. Generic APIs may not support all advanced
>>>> hardware features, while specific APIs can. Why not support all? One generic APIs for
>>>> common users, and others APIs for advanced users.
>>> Yes we cannot access to every features of a device through generic API.
>>> Until now we were trying to add an ethdev API for every features even if it
>>> is used by only one driver.
>>> I think we should allow a direct access to the driver by the applications and
>>> work on generic API only for common features.
>> Definite +1.
>> I think that we need to start pushing driver-specific functionality to get exposed
>> via a driver's header files. That allow users who want to extract the max
>> functionality from a particular NIC to do so via those APIs calls, while not
>> polluting the generic ethdev layer.
>>
> What sort of requirements on ABI/API compatibility would this place on
> the drivers? I would hope that it would be treated like any other
> public API within DPDK. I don't think this would be too onerous, but
> it would require that the drivers be designed to deal with it. (I.e.
> don't just expose any old internal driver function).

Why not to implement one simple API with variable arguments, just like
syscall ioctl() does. And drivers implement it's specific hardware
features with a feature bit param, and other needed variable arguments.

Thanks,
Michael
>> On the other hand, I don't like the idea of dpdk_netdev. I think we can work
>> within the existing rte_eth_dev framework.
>>
>> /Bruce
>>