Messages in this thread | | | Date | Fri, 18 Jun 2004 13:23:05 -0700 | From | Greg KH <> | Subject | Re: BUG(?): class_device_driver_link() |
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On Fri, Jun 18, 2004 at 04:12:32PM -0400, Alan Stern wrote: > Greg: > > I'm not sure if this is a bug or not, but it is inconsistent behavior in > sysfs. > > When a class_device is added, if it has a regular device associated with > it and that device has a driver, a symlink is added from the class_device > to the driver. However, if the class_device is added _first_ and the > driver later, this symlink is not created. It's not clear that there's > any good way to create it, especially if the class_device is added by the > bus layer and the device driver itself is unaware of the class_device.
Yes, this is the way it was designed. The thinking was that a device would be registered to a driver by the time the class code was initialized for it.
> Is this a known problem? It definitely affects the sd driver, and maybe > others.
The sd use of classes is a monumental hack. So much that every time I see one of them in the hall at work I run the other way just to avoid talking about it again :)
No, seriously, if this is a problem for the sd driver, we should fix it.
> There is a related side-effect that is a bit unpleasant. The symlink from > the class_device to the driver increments the driver's refcount.
Yes, that is a recent change.
> Since > the driver is unaware of the class_device, it doesn't know to remove the > symlink when its release() method runs.
The symlink should be removed by the class, right?
> Consequently, if the driver is > modprobed before the device exists and rmmod'ed after the device is added, > the rmmod will hang until the device also goes away. But if the driver is > modprobed _after_ the device exists then the rmmod will complete > immediately. > > Perhaps the answer is that the bus layer must take these things into > account. Or perhaps a struct device should somehow know about all the > class_devices that refer to it.
Hm, I was not wanting to have to have struct device know about classes, only classes knowing about struct devices. Any input here would be appreciated.
thanks,
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