As &struct device structure has no @owner field, and corresponding
functions rely on the @owner field at &struct device_driver, I conclude
that I cannot use &struct device objects without bus and device driver
objects, just by design.
On the other hand, 'device_register()' accepts &struct device objects
with NULL-filled @bus and @driver fields perfectly fine, does not
complain, does not return any error, and I even see corresponding
entries at /sys/devices/. But there is a refcounting problem described
at my first mail.
This is obviously a confusing discrepancy. Sysfs has to either reject
bus-less and driver-less &struct device objects or deal with them
correctly. The latter is impossible due to lack of an @owner field in
&struct device.
In connection with this, I have a question. There is a whole bunch of
drivers which do not directly relate to hardware devices, but which
still want to expose their parameters via sysfs. For example, this could
be a filesystem, LVM, a compression layer on top of a file system of a
block device, whatever. These are "virtual" devices and they are not
physically connected to any bus. How should they deal with sysfs?
I see there is the "class" stuff in sysfs, but it seems that it is far
not as flexible as the "device, driver, and bus" stuff, because I cannot
create many nested layers within classes. I can create a class, which
goes to /sys/class/, and devices within this class, which go to
/sys/class/myclass/mydev/. But I cannot create a class, devices within
that class, and daughter devices within them, like:
/sys/class/myclass/
|-- mydev1/
| -- doughterdev1/
| -- doughterdev1/
| -- ...
|-- mydev2/
|-- mydev3/
|-- ...
Please, comment this.
Thanks.
--
Best Regards,
Artem B. Bityutskiy,
St.-Petersburg, Russia.
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