linux-kernel - Re: [PATCH] PCI: hv: Fix build error without CONFIG

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Message-ID: <20190813101845.GB14977@e121166-lin.cambridge.arm.com>
Date:   Tue, 13 Aug 2019 11:18:45 +0100
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Yuehaibing <yuehaibing@...wei.com>
Cc:     Michael Kelley <mikelley@...rosoft.com>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "sashal@...nel.org" <sashal@...nel.org>,
        Dexuan Cui <decui@...rosoft.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>
Subject: Re: [PATCH] PCI: hv: Fix build error without CONFIG_SYSFS

On Sat, Jun 15, 2019 at 02:48:24PM +0800, Yuehaibing wrote:
> +cc Lorenzo Pieralisi <lorenzo.pieralisi@....com>

Can we drop this patch and merge:

https://patchwork.ozlabs.org/patch/1131444/

instead ?

Thanks,
Lorenzo

> 
> On 2019/6/15 14:18, Yuehaibing wrote:
> > 
> > On 2019/6/2 6:59, Michael Kelley wrote:
> >> From: YueHaibing <yuehaibing@...wei.com>  Sent: Friday, May 31, 2019 8:09 AM
> >>>
> >>> while building without CONFIG_SYSFS, fails as below:
> >>>
> >>> drivers/pci/controller/pci-hyperv.o: In function 'hv_pci_assign_slots':
> >>> pci-hyperv.c:(.text+0x40a): undefined reference to 'pci_create_slot'
> >>> drivers/pci/controller/pci-hyperv.o: In function 'pci_devices_present_work':
> >>> pci-hyperv.c:(.text+0xc02): undefined reference to 'pci_destroy_slot'
> >>> drivers/pci/controller/pci-hyperv.o: In function 'hv_pci_remove':
> >>> pci-hyperv.c:(.text+0xe50): undefined reference to 'pci_destroy_slot'
> >>> drivers/pci/controller/pci-hyperv.o: In function 'hv_eject_device_work':
> >>> pci-hyperv.c:(.text+0x11f9): undefined reference to 'pci_destroy_slot'
> >>>
> >>> Select SYSFS while PCI_HYPERV is set to fix this.
> >>>
> >>
> >> I'm wondering if is the right way to fix the problem.  Conceptually
> >> is it possible to setup & operate virtual PCI devices like 
> >> pci-hyperv.c does, even if sysfs is not present?  Or is it right to
> >> always required sysfs?
> >>
> >> The function pci_dev_assign_slot() in slot.c has a null implementation
> >> in include/linux/pci.h when CONFIG_SYSFS is not defined, which
> >> seems to be trying to solve the same problem for that function.  And
> >> if CONFIG_HOTPLUG_PCI is defined but CONFIG_SYSFS is not,
> >> pci_hp_create_module_link() and pci_hp_remove_module_link()
> >> look like they would have the same problem.  Maybe there should
> >> be degenerate implementations of pci_create_slot() and
> >> pci_destroy_slot() for cases when CONFIG_SYSFS is not defined?
> >>
> >> But I'll admit I don't know the full story behind how PCI slots
> >> are represented and used, so maybe I'm off base.  I just noticed
> >> the inconsistency in how other functions in slot.c are handled.
> >>
> >> Thoughts?
> > 
> > 268a03a42d33 ("PCI: drivers/pci/slot.c should depend on CONFIG_SYSFS")
> > 
> > make slot.o depends CONFIG_SYSFS
> > 
> > commit 268a03a42d3377d5fb41e6e7cbdec4e0b65cab2e
> > Author: Alex Chiang <achiang@...com>
> > Date:   Wed Jun 17 19:03:57 2009 -0600
> > 
> >     PCI: drivers/pci/slot.c should depend on CONFIG_SYSFS
> > 
> >     There is no way to interact with a physical PCI slot without
> >     sysfs, so encode the dependency and prevent this build error:
> > 
> >         drivers/pci/slot.c: In function 'pci_hp_create_module_link':
> >         drivers/pci/slot.c:327: error: 'module_kset' undeclared
> > 
> >     This patch _should_ make pci-sysfs.o depend on CONFIG_SYSFS too,
> >     but we cannot (yet) because the PCI core merrily assumes the
> >     existence of sysfs:
> > 
> >         drivers/built-in.o: In function `pci_bus_add_device':
> >         drivers/pci/bus.c:89: undefined reference to `pci_create_sysfs_dev_files'
> >         drivers/built-in.o: In function `pci_stop_dev':
> >         drivers/pci/remove.c:24: undefined reference to `pci_remove_sysfs_dev_files'
> > 
> >     So do the minimal bit for now and figure out how to untangle it
> >     later.
> > 
> > If No CONFIG_SYSFS, slot.o is not build
> > 
> >>
> >> Michael
> >>
> >>
> > 
> > 
> > .
> > 
>