On Mon, Nov 08, 2021 at 08:56:19PM -0600, Bjorn Helgaas wrote: > [+cc Greg: new device_is_bound() use] > > On Mon, Nov 08, 2021 at 10:22:26PM +0100, Uwe Kleine-König wrote: > > pci_pm_runtime_resume() exits early when the device to resume isn't > > bound yet: > > > > if (!to_pci_driver(dev->driver)) > > return 0; > > > > This however isn't true when the device currently probes and > > local_pci_probe() calls pm_runtime_get_sync() because then the driver > > core already setup dev->driver. As a result the driver's resume callback > > is called before the driver's probe function is called and so more often > > than not required driver data isn't setup yet. > > > > So replace the check for the device being unbound by a check that only > > becomes true after .probe() succeeded. > > I like the fact that this patch is short and simple. > > But there are 30+ users of to_pci_driver(). This patch asserts that > *one* of them, pci_pm_runtime_resume(), is special and needs to test > device_is_bound() instead of using to_pci_driver(). > > It's special because the current PM implementation calls it via > pm_runtime_get_sync() before the driver's .probe() method. That > connection is a little bit obscure and fragile. What if the PM > implementation changes? > > Maybe we just need a comment there about why it looks different than > the other PM interfaces? > > I also notice that the only other uses of device_is_bound() > outside the driver core are in iommu_group_store_type() and > regulator_resolve_supply(). This patch seems like a reasonable use, > but I always look twice when we do something unique. I agree that this looks really odd. No one should care outside of the driver core to call device_is_bound(), as if a driver is being called, implicitly you know that the device is bound to that driver. Why does the PCI core care if a device is bound to a pci driver at this point in time? But, this does feel like an odd use of to_pci_driver() here, what needs to be known here, if a pci driver is in control of a device here or not? thanks, greg k-h
