From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Daney Subject: Re: [PATCH v3 3/6] PCI: generic: Quit clobbering our pci_ops. Date: Wed, 23 Sep 2015 08:56:59 -0700 Message-ID: <5602CBCB.4030605@caviumnetworks.com> References: <1442965757-12925-1-git-send-email-ddaney.cavm@gmail.com> <1442965757-12925-4-git-send-email-ddaney.cavm@gmail.com> <1729894.341fjYUAKl@wuerfel> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1729894.341fjYUAKl@wuerfel> Sender: linux-pci-owner@vger.kernel.org To: Arnd Bergmann Cc: linux-arm-kernel@lists.infradead.org, David Daney , linux-kernel@vger.kernel.org, Bjorn Helgaas , linux-pci@vger.kernel.org, Will Deacon , Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , devicetree@vger.kernel.org, Marc Zyngier , David Daney List-Id: devicetree@vger.kernel.org On 09/23/2015 01:21 AM, Arnd Bergmann wrote: > On Tuesday 22 September 2015 16:49:14 David Daney wrote: >> From: David Daney >> >> The pci-host-generic driver keeps a global struct pci_ops which it >> then patches with the .map_bus method appropriate for the bus device. >> A problem arises when the driver is used for two different types of >> bus devices, the .map_bus method for the last device probed clobbers >> the method for all previous devices. The result, only the last bus >> device probed has the proper .map_bus, and the others fail. >> >> Move the struct pci_ops into the bus specific structure, and >> initialize it when the bus device is probed. Keep a copy of the >> gen_pci_cfg_bus_ops structure, instead of a pointer to a global copy, > > This is a very useful change. > >> to future proof against the addition of bus specific elements to >> struct pci_ops. > > but I don't like this part. We should just not have bus specific > elements in pci_ops. We don't really have that here either, except > that the gen_pci driver had a hack for reusing the same operations > for things that are actually different. > > It's an established practice that anything named '*_operations' is > meant to be constant and ideally defined as 'static const ... *_ops;' > in the driver. We could try to enforce this better by marking > bus->ops as 'const' and changing all the instances of this structure > accordingly. > >> @@ -65,7 +65,11 @@ static void __iomem *gen_pci_map_cfg_bus_cam(struct pci_bus *bus, >> >> static struct gen_pci_cfg_bus_ops gen_pci_cfg_cam_bus_ops = { >> .bus_shift = 16, >> - .map_bus = gen_pci_map_cfg_bus_cam, >> + .ops = { >> + .map_bus = gen_pci_map_cfg_bus_cam, >> + .read = pci_generic_config_read, >> + .write = pci_generic_config_write, >> + } >> }; > > So this is good. We could in theory unify the map_bus functions > like this now: > > static void __iomem *gen_pci_map_cfg_bus(struct pci_bus *bus, > unsigned int devfn, > int where) > { > struct gen_pci *pci = bus->sysdata; > struct gen_pci_cfg_bus_ops *ops; > resource_size_t idx; > > ops = container_of(bus->ops, struct gen_pci_cfg_bus_ops, ops); > idx = bus->number - pci->cfg.bus_range->start; > > return pci->cfg.win[idx] + ((devfn << ops->dev_shift) | where); > } > > Not sure if that improves clarity or not, up to Will. > >> @@ -234,8 +237,7 @@ static int gen_pci_probe(struct platform_device *pdev) >> } >> >> of_id = of_match_node(gen_pci_of_match, np); >> - pci->cfg.ops = of_id->data; >> + pci->cfg.ops = *(struct gen_pci_cfg_bus_ops *)of_id->data; > > This is the part that grabbed my attention, we should not do it like this. > I will consider changing this so that a structure copy is not used, perhaps as you suggest above. David Daney. > Arnd >