From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754744AbaKRNxL (ORCPT ); Tue, 18 Nov 2014 08:53:11 -0500 Received: from szxga02-in.huawei.com ([119.145.14.65]:44481 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753833AbaKRNxJ (ORCPT ); Tue, 18 Nov 2014 08:53:09 -0500 Message-ID: <546B4F18.5060705@huawei.com> Date: Tue, 18 Nov 2014 21:52:24 +0800 From: "Yun Wu (Abel)" User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:11.0) Gecko/20120327 Thunderbird/11.0.1 MIME-Version: 1.0 To: Jiang Liu CC: Thomas Gleixner , LKML , Bjorn Helgaas , Grant Likely , Marc Zyngier , Yingjoe Chen , Yijing Wang Subject: Re: [patch 08/16] genirq: Introduce callback irq_chip.irq_write_msi_msg References: <20141112133941.647950773@linutronix.de> <20141112134120.474411359@linutronix.de> <546B10DF.7020807@huawei.com> <546B4A91.6080004@huawei.com> <546B4D0D.9050601@linux.intel.com> In-Reply-To: <546B4D0D.9050601@linux.intel.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.24.136] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2014/11/18 21:43, Jiang Liu wrote: > On 2014/11/18 21:33, Yun Wu (Abel) wrote: >> On 2014/11/18 18:19, Thomas Gleixner wrote: >> >>> On Tue, 18 Nov 2014, Yun Wu (Abel) wrote: >>>> On 2014/11/12 21:43, Thomas Gleixner wrote: >>>>> struct irq_chip { >>>>> @@ -359,6 +360,7 @@ struct irq_chip { >>>>> void (*irq_release_resources)(struct irq_data *data); >>>>> >>>>> void (*irq_compose_msi_msg)(struct irq_data *data, struct msi_msg *msg); >>>>> + void (*irq_write_msi_msg)(struct irq_data *data, struct msi_msg *msg); >>>> >>>> Hmm... It's really weird. >>>> I don't think it's the interrupt controllers' responsibility to write messages >>>> for all the endpoint devices since the methods of configuring message registers >>>> may different between these devices. And theoretically, the endpoint devices >>>> themselves should take the responsibility to configure their message registers. >>>> To say the least, the write_msg callback here still need to call some certain >>>> interfaces provided by the corresponding device. >>>> >>>> There would be lots of ARM new devices capable of sending message >>>> based interrupts to interrupt controllers, does all the drivers of >>>> the devices need to expose a write_msg callback to interrupt >>>> controllers? >>> >>> Well, writing the message _IS_ part of the interrupt controller. >>> >>> So in order to enable non PCI based MSI we want to have generic >>> infrastructure with minimal per device/device class callbacks and of >>> course you need to provide that callback for your special device. >>> >>> We already have non PCI based MSI controllers in x86 today and we need >>> to handle the whole stuff with tons of copied coded extra for each of >>> those. So consolidating it into common infrastructure allows us to get >>> rid of the pointless copied code and reduce the per device effort to >>> the relevant hardware specific callbacks. irq_write_msi_msg being one >>> of those. >>> >> >> At least, we have the same goal. >> I will illustrate my thoughts by an example. >> The current code is something like: >> >> Device A >> ======== >> void A_write_msg() { ... } >> >> Group B >> (a group of devices behave same on writing messages, i.e. PCI) >> ======= >> void B_write_msg() { ... } >> >> Controller >> ========== >> irq_chip.irq_write_msi_msg () { >> if (A) >> A_write_msg(); >> if (B) >> B_write_msg(); >> } >> >> It's horrible when new devices come out, since we need to modify the >> controller part for each new device. >> What I suggested is: >> >> MSI Core >> ======== >> struct msi_ops { .write_msg, }; >> struct msi_desc { .msi_ops, }; >> >> write_msg() { >> X = get_dev(); >> irq_chip.compose_msg(X); // IRQ chips' responsibility >> X_msi_ops.write_msg(); // nothing to do with IRQ chips >> } >> >> Device A >> ======== >> void A_write_msg() { ... } >> A_msi_ops.write_msg = A_write_msg; >> >> Group B >> ======= >> void B_write_msg() { ... } >> B_msi_ops.write_msg = B_write_msg; >> >> Please correct me if I misunderstood anything. > Hi Yun, > We provide an irq_chip for each type of interrupt controller > instead of devices. For the example mentioned above, if device A > and Group B has different interrupt controllers, we just need to > implement irq_chip_A and irq_chip_B and set irq_chip.irq_write_msi_msg() > to suitable callbacks. > The framework already achieves what you you want:) What if device A and group B have the same interrupt controller? Regards, Abel