From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Wiles, Keith" Subject: Re: [PATCH] net/vhost: Add function to retreive the 'vid' for a given port id Date: Fri, 23 Sep 2016 21:23:11 +0000 Message-ID: References: <1473774463-26966-1-git-send-email-ciara.loftus@intel.com> <1673736.mOMazzh4h1@xps13> <20160922023650.GK23158@yliu-dev.sh.intel.com> <3895093.sl81aq1Okb@xps13> <20160923042641.GP23158@yliu-dev.sh.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Cc: Thomas Monjalon , "Loftus, Ciara" , "dev@dpdk.org" To: Yuanhan Liu Return-path: Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by dpdk.org (Postfix) with ESMTP id A591A6CC1 for ; Fri, 23 Sep 2016 23:23:14 +0200 (CEST) In-Reply-To: <20160923042641.GP23158@yliu-dev.sh.intel.com> Content-Language: en-US Content-ID: <5EE82A10F851C9458C47B3B811074F94@intel.com> List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" Regards, Keith > On Sep 23, 2016, at 12:26 AM, Yuanhan Liu w= rote: >=20 > 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 implemente= d in >>>>>>>> the generic ethdev API. >>>>>>>=20 >>>>>>> That means you have to add/export the PMD API first. Isn't it again= st what >>>>>>> you are proposing -- "I think we should not add any API to the PMDs= " ;) >>>>>>=20 >>>>>> 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 f= eatures >>>>>> which do not fit in a generic API. >>>>>=20 >>>>> So, does that mean you are okay with this patch now? I mean, okay to = introduce >>>>> a vhost PMD API? >>>>=20 >>>> It means I would be in favor of introducing API in drivers for very sp= ecific >>>> features. >>>> In this case, I am not sure that retrieving an internal id is very spe= cific. >>>=20 >>> 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. >>>=20 >>> 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. >>=20 >> Yes it makes sense. >> I was thinking of introducing a function to get an internal id from ethd= ev, >> 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 be= st. >=20 > Yes, that should work. But I just doubt what the "opaque pointer" could b= e > 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. >=20 > 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 co= uld cause some problems. This feels like we are talking about a IOCTL like generic interface into th= e PMD. Then we can add new one types and reject types in the PMD that are n= ot 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 specif= ic API. A number of current ethdev APIs could be removed to use the API bel= ow. The APIs would be removed from ethdev structure and have the current AP= Is 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); >=20 > If so, we may go that way. >=20 > 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? >=20 > --yliu