On Fri, Dec 04, 2009 at 06:50:35PM -0500, Alan Stern wrote: > On Fri, 4 Dec 2009, Dmitry Torokhov wrote: > > > > Maybe reference counting is inelegant; it depends on your point of > > > view. Can you think of a more elegant way to make sure that a pointer > > > isn't stale? > > > > Yes, just say "no" to device_create() and friends. > > device_create() wasn't used in the case Oliver is discussing. It was implied, as you had a pointer to the device, not the device itself. > > Embed device structure in > > yours, > > You can't do that when the device structure wasn't created by your > driver. But for USB devices, it is part of the device you are handed. Same goes for PCI devices, and most other types of drivers, right? > > be mindful of lifetime rules and only use "your" device (i.e device > > bound to your driver). > > What do you mean by "use"? In Oliver's case he wasn't using the > device, he was using the device structure. (Maybe that's what you > meant.) I think that is what is meant here. > And he wanted to use it at a time when it wasn't bound to his > driver, because userspace still had an open file reference to it. > There isn't really any way around this. But you still have a valid device, just not maybe a driver bound to it. > > This way, as long as your refcount your instance you > > can rest assured the device structure is there as well. > > I rather think that a simple device_get() and device_put() is easier > than trying to follow a bunch of rules, especially in cases where they > don't apply! :-) Like here :) thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
