From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shreyansh Jain Subject: Re: [PATCH 00/13] Introducing EAL Bus-Device-Driver Model Date: Wed, 7 Dec 2016 18:40:21 +0530 Message-ID: <1697fe66-962d-0848-5e68-615249b52dad@nxp.com> References: <1480846288-2517-1-git-send-email-shreyansh.jain@nxp.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Cc: "dev@dpdk.org" , Thomas Monjalon To: David Marchand Return-path: Received: from NAM01-SN1-obe.outbound.protection.outlook.com (mail-sn1nam01on0077.outbound.protection.outlook.com [104.47.32.77]) by dpdk.org (Postfix) with ESMTP id 8145D32A5 for ; Wed, 7 Dec 2016 14:07:37 +0100 (CET) In-Reply-To: List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On Wednesday 07 December 2016 05:47 PM, David Marchand wrote: > Hello Shreyansh, > > On Wed, Dec 7, 2016 at 10:55 AM, Shreyansh Jain wrote: >> On Wednesday 07 December 2016 02:22 AM, David Marchand wrote: >>>> 0002~0003: Introducing the basic Bus model and associated test case >>>> 0005: Support insertion of device rather than addition to tail >>> >>> >>> Patch 2 and 5 could be squashed. >> >> >> I deliberately kept them separate. I intent to extend the Patch 5 for >> hotplugging. But, if I don't end up adding support for that in this series, >> I will merge these two. > > Fine. > > >>> The constructor priority stuff seems unneeded as long as we use >>> explicit reference to a global (or local, did not check) bus symbol >>> rather than a runtime lookup. >> >> >> I didn't understand your point here. >> IMO, constructor priority (or some other way to handle this) is important. I >> faced this issue while verifying it at my end when the drivers were getting >> registered before the bus. >> >> Can you elaborate more on '..use explicit reference to a global...'? > > The drivers register themselves to a bus using this bus specific api. > > For pci, this is rte_eal_pci_register(). > The pci_bus object must be moved to eal_common_pci.c (we can stil > internally expose for bsd / linux specific implementations). > Then, rte_eal_pci_register() can add the pci driver to the pci_bus > drivers list even if this pci_bus object is not registered yet to the > buses list. So, in eal_common_bus.c --->8--- struct rte_bus *global_ptr_to_pci_bus = NULL; struct rte_bus pci_bus = { ... }; rte_eal_pci_register() { if (global_ptr_to_pci_bus == NULL) rte_eal_bus_register(&pci_bus) else // continue as if PCI bus is registered } --->8--- so, no RTE_REGISTER_BUS()? If yes, then RTE_REGISTER_BUS() should also check for an existing registration for duplication. I was banking on a model where bus handlers (or bus drivers) are independent entities, just like PMDs. So, we have a bus XYZ without any drivers necessarily based on it. By making registration dependent on driver registration, it becomes implicit that buses don't exist without drivers. I am not in favor of this - or maybe I lack enough reason for this (about how it will make framework/PMD life better). > > And no constructor order issue ? > > >>> >>> >>>> 0004: Add scan and match callbacks for the Bus and updated test case >>> >>> >>> Why do you push back the bus object in the 'scan' method ? >>> This method is bus specific which means that the code "knows" the >>> object registered with the callback. >> >> >> This 'knows' is the grey area for me. >> The bus (for example, PCI) after scanning needs to call >> rte_eal_bus_add_device() to link the device in bus's device_list. >> >> Two options: >> 1. Have a global reference to "pci" bus (rte_bus) somewhere in eal_pci.c >> 2. Call rte_eal_get_bus() every time someone needs the reference. >> 3. C++ style, 'this->'. >> >> I have taken the 3rd path. It simplifies my code to not assume a handle as >> well as not allow for reference fetch calls every now and then. >> >> As a disadvantage: it means passing this as argument - and some cases >> maintaining it as __rte_unused. >> >> Taking (1) or (2) is not advantageous than this approach. > > 1) is the simplest one. > > When you write a pci_scan method and embed it in you pci_bus object, > but this pci_scan method still wonders which bus object it is supposed > to work on, this is a bit like Schizophrenia ;-). :) This now is linked to the above issue of constructor priority and having a global bus reference. I don't personally prefer it. I will still give this a serious thought, though. > > >>> Is is that you want to have a single scan method used by multiple buses ? >> >> >> Yes, but only as a use case. For example, platform devices are of various >> types - what if we have a south-bound bus over a platform bus. In which >> case, a hierarchical bus layout is possible. >> But, this is far-fetched idea for now. > > Well, if you have no usecase at the moment, let's keep it simple, please. > Ok. > >>> >>>> 0006: Integrate bus scan/match with EAL, without any effective >>>> driver >>> >>> >>> Hard to find a right balance in patch splittng, but patch 4 and 6 are >>> linked, I would squash them into one. >> >> >> Yes, it is hard and sometimes there is simply no strong rationale for >> splitting or merging. This is one of those cases. >> My idea was that one patch _only_ introduces Bus services (structures, >> functions etc) and another should enable the calls to it from EAL. >> In that sense, I still think 4 and 6 should remain separate, may be >> consecutive, though. > > Ok, will see in next version of the patchset. Is there anything specific that you are looking for in patchset v2? I was thinking of: 0. fixing BSD compilation issue reported by CI 1. improving the test_pci.c 2. hotplugging 3. trying to move PCI to drives/bus/pci/linux/* and resolving how drivers link to it, and how EAL resources like devargs are consumed. Anything else? > > >>> >>>> 0007: rte_pci_driver->probe replaced with rte_driver->probe >>> >>> >>> This patch is too big, please separate in two patches: eal changes >>> then ethdev/driver changes. >> >> >> I don't think that can be done. One change is incomplete without the other. >> >> Changes to all files are only for rte_pci_driver->probe to rte_driver->probe >> movement. EAL changes is to allow rte_eth_dev_pci_probe function after such >> a change as rte_driver->probe has different arguments as compared to >> rte_pci_driver->probe. The patches won't compile if I split. >> >> Am I missing something? >>> >>> Why do you push back the driver object in the 'probe' method ? (idem >>> rte_bus->scan). >> >> >> I am assuming you are referring to rte_driver->probe(). >> This is being done so that implementations (specific to drivers on a >> particular bus) can start extracting the rte_xxx_driver, if need be. >> >> For example, for e1000/em_ethdev.c, rte_driver->probe() have been set to >> rte_eth_dev_pci_probe() which requires rte_pci_driver to work with. In >> absence of the rte_driver object, this function cannot call >> rte_pci_driver->probe (for example) for driver specific operations. > > Sorry, I am thinking a step ahead with eth_driver out of the picture. > But once eth_driver disappears, I can see no reason to keep this > driver in the probe method (Schizophrenia again). When eth_driver disappears, i was thinking of accomodating the eth_dev_init into the rte_pci_driver->probe/init. But, this is still a nascent thought. I am yet to start working on eth_driver. > > >