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    SubjectRe: [PATCH v4 01/30] PCI: Rip out pci_bus_add_devices() from pci_scan_bus()
    On Thu, Feb 26, 2015 at 04:11:55PM +0800, Yijing Wang wrote:
    > Pci_bus_add_devices() should not be placed in pci_scan_bus().
    > Now pci device will be added to driver core once its
    > creation. All things left in pci_bus_add_devices() are
    > driver attachment and other trivial sysfs things.
    > Pci_scan_bus() should be the function responsible for
    > scanning PCI devices, not including driver attachment.
    > Other, some callers(m68k,unicore32,alpha) of pci_scan_bus()
    > will call pci_bus_size_bridges() and pci_bus_assign_resources()
    > after pci_scan_bus().
    >
    > E.g.
    > In m68k
    > mcf_pci_init()
    > pci_scan_bus()
    > ...
    > pci_bus_add_devices() --- try to attach driver
    > pci_fixup_irqs()
    > pci_bus_size_bridges()
    > pci_bus_assign_resources()
    >
    > Above code flow make pci scan logic obscure, resources should
    > be assigned correctly before attaching driver. Because
    > pci_scan_bus() mostly be called in system boot path, when
    > before drivers are loaded(in module_init), so no pci scan
    > issues will occur. Most pci_scan_bus() callers additionally
    > call pci_bus_size_bridges() and pci_bus_assign_resources()
    > after pci_scan_bus(), we could rip out pci_bus_add_devices()
    > for better code readability. After applied this patch,
    > pci_scan_bus() should be used like:
    >
    > pci_scan_bus() (mandatory)
    > pci_fixup_irqs() (optional)
    > pci_bus_size_bridges() (optional)
    > pci_pci_bus_assign_resources() (optional)
    > pci_bus_add_devices() (mandatory)
    >
    > Signed-off-by: Yijing Wang <wangyijing@huawei.com>
    > CC: "David S. Miller" <davem@davemloft.net>
    > CC: Geert Uytterhoeven <geert@linux-m68k.org>
    > CC: Guan Xuetao <gxt@mprc.pku.edu.cn>
    > CC: Richard Henderson <rth@twiddle.net>
    > CC: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
    > CC: Matt Turner <mattst88@gmail.com>
    > CC: linux-alpha@vger.kernel.org
    > CC: linux-m68k@lists.linux-m68k.org
    > CC: sparclinux@vger.kernel.org
    > ---
    > arch/alpha/kernel/sys_nautilus.c | 1 +
    > arch/m68k/coldfire/pci.c | 1 +
    > arch/sparc/kernel/pcic.c | 2 ++
    > arch/unicore32/kernel/pci.c | 11 +++--------
    > drivers/pci/hotplug/ibmphp_core.c | 6 ++++--
    > drivers/pci/probe.c | 1 -
    > 6 files changed, 11 insertions(+), 11 deletions(-)
    >
    > diff --git a/arch/alpha/kernel/sys_nautilus.c b/arch/alpha/kernel/sys_nautilus.c
    > index 837c0fa..4ae4a40 100644
    > --- a/arch/alpha/kernel/sys_nautilus.c
    > +++ b/arch/alpha/kernel/sys_nautilus.c
    > @@ -253,6 +253,7 @@ nautilus_init_pci(void)
    > for the root bus, so just clear it. */
    > bus->self = NULL;
    > pci_fixup_irqs(alpha_mv.pci_swizzle, alpha_mv.pci_map_irq);
    > + pci_bus_add_devices(bus);
    > }
    >
    > /*
    > diff --git a/arch/m68k/coldfire/pci.c b/arch/m68k/coldfire/pci.c
    > index df96792..d45f087 100644
    > --- a/arch/m68k/coldfire/pci.c
    > +++ b/arch/m68k/coldfire/pci.c
    > @@ -319,6 +319,7 @@ static int __init mcf_pci_init(void)
    > pci_fixup_irqs(pci_common_swizzle, mcf_pci_map_irq);
    > pci_bus_size_bridges(rootbus);
    > pci_bus_assign_resources(rootbus);
    > + pci_bus_add_devices(rootbus);
    > return 0;
    > }
    >
    > diff --git a/arch/sparc/kernel/pcic.c b/arch/sparc/kernel/pcic.c
    > index 6cc78c2..7a82fe2 100644
    > --- a/arch/sparc/kernel/pcic.c
    > +++ b/arch/sparc/kernel/pcic.c
    > @@ -391,6 +391,8 @@ static void __init pcic_pbm_scan_bus(struct linux_pcic *pcic)
    > struct linux_pbm_info *pbm = &pcic->pbm;
    >
    > pbm->pci_bus = pci_scan_bus(pbm->pci_first_busno, &pcic_ops, pbm);
    > + if (pbm->pci_bus)
    > + pci_bus_add_devices(pbm->pci_bus);
    > #if 0 /* deadwood transplanted from sparc64 */
    > pci_fill_in_pbm_cookies(pbm->pci_bus, pbm, pbm->prom_node);
    > pci_record_assignments(pbm, pbm->pci_bus);

    This is correct, but it should look like this instead:

    if (!pbm->pci_bus)
    return;
    #if 0 /* deadwood ... */
    ...
    #endif
    pci_bus_add_devices(pbm->pci_bus);
    }

    That way the mainline code is the normal path, and pci_bus_add_devices() is
    in the correct place even if the "deadwood" code is resurrected.


    > diff --git a/arch/unicore32/kernel/pci.c b/arch/unicore32/kernel/pci.c
    > index 374a055..3d82024 100644
    > --- a/arch/unicore32/kernel/pci.c
    > +++ b/arch/unicore32/kernel/pci.c
    > @@ -266,17 +266,12 @@ static int __init pci_common_init(void)
    > pci_fixup_irqs(pci_common_swizzle, pci_puv3_map_irq);
    >
    > if (!pci_has_flag(PCI_PROBE_ONLY)) {
    > - /*
    > - * Size the bridge windows.
    > - */
    > + /* Size the bridge windows. */
    > pci_bus_size_bridges(puv3_bus);
    > -
    > - /*
    > - * Assign resources.
    > - */
    > + /* Assign resources. */
    > pci_bus_assign_resources(puv3_bus);
    > }
    > -
    > + pci_bus_add_devices(puv3_bus);
    > return 0;
    > }
    > subsys_initcall(pci_common_init);
    > diff --git a/drivers/pci/hotplug/ibmphp_core.c b/drivers/pci/hotplug/ibmphp_core.c
    > index 96c5c72..86e3bfd 100644
    > --- a/drivers/pci/hotplug/ibmphp_core.c
    > +++ b/drivers/pci/hotplug/ibmphp_core.c
    > @@ -738,7 +738,7 @@ static void ibm_unconfigure_device(struct pci_func *func)
    > */
    > static u8 bus_structure_fixup(u8 busno)
    > {
    > - struct pci_bus *bus;
    > + struct pci_bus *bus, *b;
    > struct pci_dev *dev;
    > u16 l;
    >
    > @@ -765,7 +765,9 @@ static u8 bus_structure_fixup(u8 busno)
    > (l != 0x0000) && (l != 0xffff)) {
    > debug("%s - Inside bus_structure_fixup()\n",
    > __func__);
    > - pci_scan_bus(busno, ibmphp_pci_bus->ops, NULL);
    > + b = pci_scan_bus(busno, ibmphp_pci_bus->ops, NULL);
    > + if (b)
    > + pci_bus_add_devices(b);

    Use this:

    if (!b)
    continue;
    pci_bus_add_devices(b);

    for the same reason as above.

    > break;
    > }
    > }
    > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
    > index 8d2f400..88604f2 100644
    > --- a/drivers/pci/probe.c
    > +++ b/drivers/pci/probe.c
    > @@ -2123,7 +2123,6 @@ struct pci_bus *pci_scan_bus(int bus, struct pci_ops *ops,
    > b = pci_create_root_bus(NULL, bus, ops, sysdata, &resources);
    > if (b) {
    > pci_scan_child_bus(b);
    > - pci_bus_add_devices(b);
    > } else {
    > pci_free_resource_list(&resources);
    > }
    > --
    > 1.7.1
    >


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