Messages in this thread | ![/](/images/icornerl.gif) | | Date | Tue, 29 Mar 2005 11:18:13 -0500 (EST) | From | Alan Stern <> | Subject | Re: klists and struct device semaphores |
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On Mon, 28 Mar 2005, Patrick Mochel wrote:
> How is this related to (8) above? Do you need some sort of protected, > short path through the core to add the device, but not bind it or add it > to the PM core?
Having thought it through, I believe all we need for USB support is this:
Whenever usb_register() in the USB core calls driver_register() and the call filters down to driver_attach(), that routine should lock dev->parent->sem before calling driver_probe_device() (and unlock it afterward, of course).
(For the corresponding remove pathway, where usb_deregister() calls driver_unregister(), it would be nice if __remove_driver() locked dev->parent->sem before calling device_release_driver(). This is not really needed, however, since USB drivers aren't supposed to touch the device in their disconnect() method.)
With that change in place we can guarantee that every time a USB driver's probe() is called, both the interface and the parent device are locked.
I don't know how cleanly this can be implemented. You probably don't want to lock dev->parent->sem every time, only when needed. Maybe the simplest approach would be to add a flag in struct bus_type, which could be set for the USB bus_type and clear for everything else.
Alan Stern
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