From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yuanhan Liu Subject: Re: [PATCH] net/vhost: Add function to retreive the 'vid' for a given port id Date: Mon, 26 Sep 2016 11:19:42 +0800 Message-ID: <20160926031942.GG23158@yliu-dev.sh.intel.com> 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 Cc: Thomas Monjalon , "Loftus, Ciara" , "dev@dpdk.org" To: "Wiles, Keith" Return-path: Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by dpdk.org (Postfix) with ESMTP id F38ED2BA1 for ; Mon, 26 Sep 2016 05:19:18 +0200 (CEST) Content-Disposition: inline In-Reply-To: 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" On Fri, Sep 23, 2016 at 09:23:11PM +0000, Wiles, Keith wrote: > > Regards, > Keith > > > On Sep 23, 2016, at 12:26 AM, Yuanhan Liu 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. Yes, that's what I meant. > Not sure what any application would need with the FD here, as it could cause some problems. Me, neither. > 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); Looks like a very clean solution to me! Thomas? --yliu > > > > > 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