On Mon, Sep 28, 2020 at 06:43:55PM -0700, Matthias Kaehlcke wrote: > > Have you tried manually unbinding and rebinding the two drivers a few > > times to make sure they will still work? > > I went through a few dozen bund/unbind cycles for both drivers and things > looked good overall, but then last minute I found that determining whether > wakeup capable devices are connected doesn't always work as (I) expected. > I didn't see this earlier, it seems to be reproduce more easily after > unbinding and rebinding the platform driver. > > During development I already noticed that usb_wakeup_enabled_descendants() > returns a cached value, which was a problem for an earlier version of the > driver. The values are updated by hub_suspend(), my (flawed) assumption > was that the USB driver would always suspend before the platform driver. > This generally seems to be the case on my development platform after boot, > but not necessarily after unbinding and rebinding the driver. Using the > _suspend_late hook instead of _suspend seems to be a reliable workaround. Yes, for unrelated (i.e., not in a parent-child relation) devices, the PM subsystem doesn't guarantee ordering of suspend and resume callbacks. You can enforce the ordering by using device_pm_wait_for_dev(). But the suspend_late approach seems like a better solution in this case. > > I'm a little concerned about all the devm_* stuff in here; does that > > get released when the driver is unbound from the device or when the device > > is unregistered? And if the latter, what happens if you have multiple > > sysfs attribute groups going at the same time? > > The memory gets released when the device is unbound: > > device_release_driver > device_release_driver_internal > __device_release_driver > devres_release_all > > Anyway, if you prefer I can change the driver to use kmalloc/kfree. No, that's fine. I just wasn't sure about this and wanted to check. Alan Stern
