Regards,
Keith
> On Sep 23, 2016, at 12:26 AM, Yuanhan Liu <yuanhan.liu at linux.intel.com>
> wrote:
>
> On Thu, Sep 22, 2016 at 06:43:55PM +0200, Thomas Monjalon wrote:
>>>>>>>> There could be a similar need in other PMD.
>>>>>>>> If we can get an opaque identifier of the device which is not the port
>>>>>>>> id,
>>>>>>>> we could call some specific functions of the driver not implemented in
>>>>>>>> the generic ethdev API.
>>>>>>>
>>>>>>> That means you have to add/export the PMD API first. Isn't it against
>>>>>>> what
>>>>>>> you are proposing -- "I think we should not add any API to the PMDs" ;)
>>>>>>
>>>>>> Yes you are totally right :)
>>>>>> Except that in vhost case, we would not have any API in the PMD.
>>>>>> But it would allow to have some specific API in other PMDs for the
>>>>>> features
>>>>>> which do not fit in a generic API.
>>>>>
>>>>> So, does that mean you are okay with this patch now? I mean, okay to
>>>>> introduce
>>>>> a vhost PMD API?
>>>>
>>>> It means I would be in favor of introducing API in drivers for very
>>>> specific
>>>> features.
>>>> In this case, I am not sure that retrieving an internal id is very
>>>> specific.
>>>
>>> It's not, instead, it's very generic. The "internal id" is actually the
>>> public interface to vhost-user application, like "fd" to file APIs.
>>>
>>> Instead of introducing a few specific wrappers/APIs, I'd prefer to
>>> introduce a generic one to get the handle, and let the application to
>>> call other vhost APIs.
>>
>> Yes it makes sense.
>> I was thinking of introducing a function to get an internal id from ethdev,
>> in order to use it with any driver or underlying library.
>> But it would be an opaque pointer and you need an int.
>> Note that we can cast an int into a pointer, so I am not sure what is best.
>
> Yes, that should work. But I just doubt what the "opaque pointer" could be
> for other PMD drivers, and what the application could do with it. For a
> typical nic PMD driver, I can think of nothing is valuable to export to
> user applications.
>
> But maybe it's valuable to other virtual PMD drives as well, like the TAP
> pmd from Keith?
I do not see a need in the TAP PMD other then returning the FD for TUN/TAP
device. Not sure what any application would need with the FD here, as it could
cause some problems.
This feels like we are talking about a IOCTL like generic interface into the
PMD. Then we can add new one types and reject types in the PMD that are not
supported. Would this not be a better method for all future PMD APIs?
Here is just a thought as to how to solve this problem without a PMD specific
API. A number of current ethdev APIs could be removed to use the API below. The
APIs would be removed from ethdev structure and have the current APIs use the
API below. I know some are not happy with number of APIs in the ethdev
structure.
The API could be something like this:
struct rte_tlv { /* Type/Length/Value like structure */
uint16_t type; /* Type of command */
uint16_t len; /* Length of data section on input and on output */
uint16_t tlen; /* Total or max length of data buffer */
uint8_t data[0];
};
int rte_eth_dev_ioctl(int pid, int qid, struct rte_tlv *tlv);
>
> If so, we may go that way.
>
> Another thought is that, it may be a bit weird to me to introduce an API
> to get an opaque pointer. I mean, it's a bit hard to document it, because
> it has different meaning for different drivers. Should we list all of
> them then?
>
> --yliu
