On 4/19/07, Cornelia Huck <[email protected]> wrote:
On Thu, 19 Apr 2007 09:13:43 -0400,
"Dmitry Torokhov" <[email protected]> wrote:
> Because they are managed by 2 different entities. the struct device
> objects are managed by device core and driver-specific objects are
> managed by their respective driver.
Not sure if I understand you here. My view of this was always that the
embedding object was kind of an extended device and that the relevant
driver/subsystem managed it through the driver core infrastructure.
I am not sure if I agree with this point of view. Driver (or
subsystem) provides an instance of struct device for the rest of the
system to iteract uniformly with (suspend/resume/tree
visualization/etc) i.e. struct device implement an interface for
subsystems. However most of the system use their own mechanisms to
manage their devices. They can rely on the driver core to a certain
degree but driver core is mostly a carries out helper functions, not
the meat.
>
> > > Pretty much drivers have 2 options:
> > >
> > > struct my_device {
> > > void *private_data;
> > > struct device dev;
> > > };
> > >
> > > In this case ->release must live in a subsystem code; individual
> > > drivers kfree(my_dev->private) and do any additional cleanup after
> > > calling device_unregister(&my_dev->dev);
> >
> > They must do this in the ->remove callback.
>
> Why? If the driver truly stops hardware then any driver-specific data
> is not needed. With sysfs severing access to removed attributes there
> is no need to gave "global release", cleanup can be done in stages.
I think I meant the same thing :) Freeing the data in the ->release
callback is obviously too late. Freeing it in the ->remove callback
means that the device is no longer really used (and can't be looked up
any more); only some further refrences may linger (and those are of no
consequence with the sysfs disconnect).
Ah, right, I confused ->remove() with ->release() in your post. Sorry
about that.
--
Dmitry
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