From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg Ungerer Subject: Re: [PATCH 01/28] PCI: Rip out pci_bus_add_devices() from pci_scan_bus() Date: Mon, 19 Jan 2015 14:59:44 +1000 Message-ID: <54BC8F40.1080405@westnet.com.au> References: <1421372666-12288-1-git-send-email-wangyijing@huawei.com> <1421372666-12288-2-git-send-email-wangyijing@huawei.com> <54BC6611.9020002@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <54BC6611.9020002@huawei.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Yijing Wang , Yinghai Lu Cc: Liviu Dudau , Tony Luck , Russell King , Arnd Bergmann , Marc Zyngier , "linux-pci@vger.kernel.org" , the arch/x86 maintainers , Linux Kernel Mailing List , "David S. Miller" , "sparclinux@vger.kernel.org" , linux-m68k@lists.linux-m68k.org, Geert Uytterhoeven , linux-alpha@vger.kernel.org, Bjorn Helgaas , "linux-ia64@vger.kernel.org" , Thomas Gleixner , Guan Xuetao , Jiang Liu , "linux-arm-kernel@lists.infradead.org" On 19/01/15 12:04, Yijing Wang wrote: > On 2015/1/17 7:16, Yinghai Lu wrote: >> On Fri, Jan 16, 2015 at 3:15 PM, Yinghai Lu wrote: >>> On Thu, Jan 15, 2015 at 5:43 PM, 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() >>>> >>>> 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. I agree that ordering seems odd. I recall there was a reason I had to put it in that order (at that time - which is a few years back now). I can't remember exactly now, but it was something like bridges didn't get resourced properly without a pci scan first. Regards Greg