Messages in this thread | | | Subject | Re: [PATCH v3 1/9] s390: vfio_ap: link the vfio_ap devices to the vfio_ap bus subsystem | From | Pierre Morel <> | Date | Thu, 14 Feb 2019 16:47:30 +0100 |
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On 14/02/2019 15:54, Cornelia Huck wrote: > On Thu, 14 Feb 2019 14:51:01 +0100 > Pierre Morel <pmorel@linux.ibm.com> wrote: > >> Libudev relies on having a subsystem link for non-root devices. To >> avoid libudev (and potentially other userspace tools) choking on the >> matrix device let us introduce a vfio_ap bus and with that the vfio_ap >> bus subsytem, and make the matrix device reside within it. > > How does libudev choke on this? It feels wrong to introduce a bus that > basically does nothing...
Christian answered this in another thread, so I don't answer.
> >> >> We restrict the number of allowed devices to a single one. >> ...snip...
>> +++ 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.
> >> >> 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?
-- Pierre Morel Linux/KVM/QEMU in Böblingen - Germany
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