From mboxrd@z Thu Jan  1 00:00:00 1970
From: Yijing Wang <wangyijing@huawei.com>
Subject: Re: [PATCH 01/28] PCI: Rip out pci_bus_add_devices() from pci_scan_bus()
Date: Mon, 19 Jan 2015 10:04:01 +0800
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To: Yinghai Lu <yinghai@kernel.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>, Jiang Liu <jiang.liu@linux.intel.com>, "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Marc Zyngier <marc.zyngier@arm.com>, "linux-arm-kernel@lists.infradead.org" <linux-arm-kernel@lists.infradead.org>, Russell King <linux@arm.linux.org.uk>, the arch/x86 maintainers <x86@kernel.org>, Thomas Gleixner <tglx@linutronix.de>, Tony Luck <tony.luck@intel.com>, "linux-ia64@vger.kernel.org" <linux-ia64@vger.kernel.org>, "David S. Miller" <davem@davemloft.net>, Guan Xuetao <gxt@mprc.pku.edu.cn>, linux-alpha@vger.kernel.org, linux-m68k@lists.linux-m68k.org, Liviu Dudau <liviu@dudau.co.uk>, Arnd Bergmann <arnd@arndb.de>, Geert Uytterhoeven <geert@linux-m68k.org>, "sparclinux@vger.kernel.org" <sparclinux@vger.kernel.org>

On 2015/1/17 7:16, Yinghai Lu wrote:
> On Fri, Jan 16, 2015 at 3:15 PM, Yinghai Lu <yinghai@kernel.org> wrote:
>> On Thu, Jan 15, 2015 at 5:43 PM, Yijing Wang <wangyijing@huawei.com> 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()
>>>
>>> It is not correct, resources should be assigned correctly
>>> before attaching driver.
>>
> No, for booting path, at that time pci drivers are *NOT* loaded yet.

Hi Yinghai, I knew code flow here would not cause problems, sorry the log
confused you, I will refresh it. But I think pci_scan_bus()/pci_scan_root_bus()
which could only be used during system boot up(before module_init) make
the pci scan logic obscure. Because most callers additionally call
pci_bus_size_bridges() and pci_bus_assign_resources() later,
so rip out pci_bus_add_devices() from pci_scan_bus()/pci_scan_root_bus()
make code have better readability.

Thanks!
Yijing.

> 
> Thanks
> 
> Yinghai
> 
> .
> 


-- 
Thanks!
Yijing