From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pierre Morel Subject: Re: [PATCH v3 1/9] s390: vfio_ap: link the vfio_ap devices to the vfio_ap bus subsystem Date: Thu, 14 Feb 2019 18:36:46 +0100 Message-ID: <9200b1f8-874f-ffa7-bef0-19ca570d7ac1@linux.ibm.com> References: <1550152269-6317-1-git-send-email-pmorel@linux.ibm.com> <1550152269-6317-2-git-send-email-pmorel@linux.ibm.com> <20190214155441.087d2a68.cohuck@redhat.com> <9403117a-04a6-8f69-2a61-f96d35a59555@linux.ibm.com> <20190214175730.4ab609ae.cohuck@redhat.com> Reply-To: pmorel@linux.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format="flowed" Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20190214175730.4ab609ae.cohuck@redhat.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Archive: List-Post: To: Cornelia Huck Cc: borntraeger@de.ibm.com, alex.williamson@redhat.com, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, kvm@vger.kernel.org, frankja@linux.ibm.com, akrowiak@linux.ibm.com, pasic@linux.ibm.com, david@redhat.com, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, freude@linux.ibm.com, mimu@linux.ibm.com List-ID: On 14/02/2019 17:57, Cornelia Huck wrote: > On Thu, 14 Feb 2019 16:47:30 +0100 Pierre Morel > wrote: > >> On 14/02/2019 15:54, Cornelia Huck wrote: >>> On Thu, 14 Feb 2019 14:51:01 +0100 Pierre Morel >>> wrote: > >>>> +++ b/drivers/s390/crypto/vfio_ap_drv.c @@ -24,8 +24,9 @@ >>>> MODULE_LICENSE("GPL v2"); >>>> >>>> static struct ap_driver vfio_ap_drv; >>>> >>>> -static struct device_type vfio_ap_dev_type = { - .name = >>>> VFIO_AP_DEV_TYPE_NAME, +struct matrix_driver { + struct >>>> device_driver drv; + int device_count; >>> >>> This counter basically ensures that at most one device may bind >>> with this driver... you'd still have that device on the bus, >>> though. >> >> yes, this is what is wanted: this driver can only support one >> device. May be another matrix driver can support one or more other >> devices. >> >> I should update comment message my be. >> >>> >>>> }; >>>> >>>> struct ap_matrix_dev *matrix_dev; >> >>>> >>>> - matrix_dev->device.type = &vfio_ap_dev_type; >>>> dev_set_name(&matrix_dev->device, "%s", VFIO_AP_DEV_NAME); >>>> matrix_dev->device.parent = root_device; + >>>> matrix_dev->device.bus = &matrix_bus; >>>> matrix_dev->device.release = vfio_ap_matrix_dev_release; - >>>> matrix_dev->device.driver = &vfio_ap_drv.driver; + >>>> matrix_dev->vfio_ap_drv = &vfio_ap_drv; >>> >>> Can't you get that structure through matrix_dev->device.driver >>> instead when you need it in the function below? >> >> Not anymore. We have two different drivers and devices matrix_drv >> <-> matrix_dev and vfio_ap_drv <-> ap_devices >> >> The driver behind the matrix_dev->dev->driver is matrix_drv what is >> needed here is vfio_ap_drv. > > Wait, we had tacked a driver for ap devices unto a matrix device, > which is not on the ap bus? ...yes -( > Maybe that's what trips libudev? > > (And reading further in the current code, it seems we clear that > structure _after_ the matrix device had been setup, so how can that > even work? Where am I confused?) On device_register there were no bus, so the core just do not look for a driver and this field was nor tested nor overwritten. > >> >>> >>>> >>>> ret = device_register(&matrix_dev->device); if (ret) goto >>>> matrix_reg_err; >>>> >>>> + ret = driver_register(&matrix_driver.drv); + if (ret) + goto >>>> matrix_drv_err; + >>> >>> As you already have several structures that can be registered >>> exactly once (the root device, the bus, the driver, ...), you can >>> already be sure that there's only one device on the bus, can't >>> you? >> >> hum, no I don't think so, no device can register before this module >> is loaded, but what does prevent a device to register later from >> another module? > > Not unless you export the interface, I guess. > :) definitively right thanks, this will simplify the code in the next version. I will take the patch away from this series to get the way to stable as Christian requested. Regards, Pierre -- Pierre Morel Linux/KVM/QEMU in Böblingen - Germany