From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yijing Wang Subject: Re: [PATCH v2 06/22] PCI/MSI: Introduce weak arch_find_msi_chip() to find MSI chip Date: Fri, 26 Sep 2014 10:33:24 +0800 Message-ID: <5424D074.60102__18466.4808017716$1411699133$gmane$org@huawei.com> References: <1411614872-4009-1-git-send-email-wangyijing@huawei.com> <1411614872-4009-7-git-send-email-wangyijing@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta4.messagelabs.com ([85.158.143.247]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1XXLOw-0002Fm-B3 for xen-devel@lists.xenproject.org; Fri, 26 Sep 2014 02:36:54 +0000 In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Thomas Gleixner Cc: linux-mips@linux-mips.org, linux-ia64@vger.kernel.org, linux-pci@vger.kernel.org, Bharat.Bhushan@freescale.com, Thierry Reding , sparclinux@vger.kernel.org, linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, Russell King , Michael Ellerman , Joerg Roedel , x86@kernel.org, Sebastian Ott , Benjamin Herrenschmidt , xen-devel@lists.xenproject.org, arnab.basu@freescale.com, Arnd Bergmann , Chris Metcalf , Bjorn Helgaas , linux-arm-kernel@lists.infradead.org, Thomas Petazzoni , Xinwei Hu , Tony Luck , Sergei Shtylyov , linux-kernel@vger.kernel.org List-Id: xen-devel@lists.xenproject.org On 2014/9/25 18:38, Thomas Gleixner wrote: > On Thu, 25 Sep 2014, Yijing Wang wrote: > >> Introduce weak arch_find_msi_chip() to find the match msi_chip. >> Currently, MSI chip associates pci bus to msi_chip. Because in >> ARM platform, there may be more than one MSI controller in system. >> Associate pci bus to msi_chip help pci device to find the match >> msi_chip and setup MSI/MSI-X irq correctly. But in other platform, >> like in x86. we only need one MSI chip, because all device use >> the same MSI address/data and irq etc. So it's no need to associate >> pci bus to MSI chip, just use a arch function, arch_find_msi_chip() >> to return the MSI chip for simplicity. The default weak >> arch_find_msi_chip() used in ARM platform, find the MSI chip >> by pci bus. > > This is really backwards. On one hand you try to get rid of the weak > arch functions zoo and then you invent new ones for no good > reason. Why can't x86 store the chip in the pci bus? Hi Thomas, I introduced this weak function , because I thought all platforms except arm always have only one msi chip, and I hoped to provide a simplest solution, less code changes. I consider several solutions to associate msi chip and PCI device. In my reply to Thierry in first reply, http://marc.info/?l=linux-pci&m=141169658208255&w=2 Could you give me some advices ? Thanks! Yijing. > > Looking deeper, I'm questioning the whole notion of different > msi_chips. Are this really different MSI controllers with a different > feature set or are this defacto multiple instances of the same > controller which just need a different data set? > > Thanks, > > tglx > > . > -- Thanks! Yijing