From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Monjalon Subject: Re: [PATCH v3 1/2] ethdev: add capability control API Date: Mon, 06 Mar 2017 21:21:33 +0100 Message-ID: <10140076.z0k8vql8dv@xps13> References: <1488589820-206947-1-git-send-email-cristian.dumitrescu@intel.com> <12629083.yAQ7FffjSn@xps13> <3EB4FA525960D640B5BDFFD6A3D891265275B202@IRSMSX108.ger.corp.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Cc: dev@dpdk.org, "jerin.jacob@caviumnetworks.com" , "balasubramanian.manoharan@cavium.com" , "hemant.agrawal@nxp.com" , "shreyansh.jain@nxp.com" , "Wiles, Keith" , "Richardson, Bruce" To: "Dumitrescu, Cristian" Return-path: Received: from mail-wr0-f172.google.com (mail-wr0-f172.google.com [209.85.128.172]) by dpdk.org (Postfix) with ESMTP id 3D666914 for ; Mon, 6 Mar 2017 21:21:35 +0100 (CET) Received: by mail-wr0-f172.google.com with SMTP id l37so125151344wrc.1 for ; Mon, 06 Mar 2017 12:21:35 -0800 (PST) In-Reply-To: <3EB4FA525960D640B5BDFFD6A3D891265275B202@IRSMSX108.ger.corp.intel.com> List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" > From: Thomas Monjalon [mailto:thomas.monjalon@6wind.com] > > 2017-03-06 16:35, Dumitrescu, Cristian: > > > > > +int rte_eth_dev_capability_ops_get(uint8_t port_id, > > > > > + enum rte_eth_capability cap, void *arg); > > > > > > > > What is the benefit of getting different kind of capabilities with > > > > the same function? > > > > enum + void* = ioctl > > > > A self-explanatory API should have a dedicated function for each kind > > > > of features with different argument types. > > > > > > The advantage is providing a standard interface to query the capabilities of > > the device rather than having each capability provide its own mechanism in a > > slightly different way. > > > > > > IMO this mechanism is of great help to guide the developers of future > > ethdev features on the clean path to add new features in a modular way, > > extending the ethdev functionality while doing so in a separate name space > > and file (that's why I tend to call this a plugin-like mechanism), as opposed to > > the current monolithic approach for ethdev, where we have 100+ API > > functions in a single name space and that are split into functional groups just > > by blank lines in the header file. It is simply the generalization of the > > mechanism introduced by rte_flow in release 17.02 (so all the credit should > > go to Adrien and not me). > > > > > > IMO, having a standard function as above it cleaner than having a separate > > and slightly different function per feature. People can quickly see the set of > > standard ethdev capabilities and which ones are supported by a specific > > device. Between A) and B) below, I definitely prefer A): > > > A) status = rte_eth_dev_capability_ops_get(port_id, > > RTE_ETH_CABABILITY_TM, &tm_ops); > > > B) status = rte_eth_dev_tm_ops_get(port_id, &tm_ops); > > > > I prefer B because instead of tm_ops, you can use some specific tm > > arguments, > > show their types and properly document each parameter. > > Note that rte_flow already returns the flow ops as a void * with no strong argument type checking (approach A from above). Are you saying this is wrong? > > rte_eth_dev_filter_ctrl(port_id, RTE_ETH_FILTER_GENERIC, RTE_ETH_FILTER_GET, void *eth_flow_ops); > > Personally, I am in favour of allowing the standard interface at the expense of strong build-time type checking. Especially that this API function is between ethdev and the drivers, as opposed to between app and ethdev. rte_eth_dev_filter_ctrl is going to be specialized in rte_flow operations. I agree with you on having independent API blocks in ethdev like rte_flow. But this function rte_eth_dev_capability_ops_get that you propose would be cross-blocks. I don't see the benefit. I especially don't think there is a sense in the enum enum rte_eth_capability { RTE_ETH_CAPABILITY_FLOW = 0, /**< Flow */ RTE_ETH_CAPABILITY_TM, /**< Traffic Manager */ RTE_ETH_CAPABILITY_MAX } I won't debate more on this. We have to read opinions of other reviewers.