Am Donnerstag, 12. Dezember 2002 18:34 schrieb Oliver Kurth:
> Hello!
>
> I am currently trying to write a driver for a wireless usb adapter. There
> already is a driver existing, but it is buggy, the code is messy, and
> so I do not even want to try to fix it. So I thought this is a good
> opportunity to learn writing device drivers.
>
> The driver needs to load a (propritary) firmware to the device. I do
> this in the probe() function, and the first part of it works. After
> downloading, it has to call usb_reset_device() (at least the old
> driver does). When I do this, the driver hangs.
>
> Before the reset, there are a lot of calls to usb_control_msg(), all
> of them work as expected. Then it sleeps for 2 seconds, using
>
> set_current_state(TASK_INTERRUPTIBLE);
> schedule_timeout(2*HZ);
>
> Shortly after that, usb_reset_device() is called, and it hangs.
>
> I haven't set any locks.
You haven't but usbcore has.
down(&driver->serialize);
private = driver->probe(dev,ifnum,id);
up(&driver->serialize);
This is how probe() is called.
down(&driver->serialize);
driver->disconnect(dev, interface->private_data);
up(&driver->serialize);
And this is how disconnect() is called. The deadlock is obvious.
For 2.4 I suggest that you do the reset by hand. 2.5 will need to seperate
physical and logical reset.
HTH
Oliver
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