On 31/01/2013 14:23, Laszlo Ersek wrote:
Hi,
I'm working on propagating errors out to do_device_add(). I've come
accross qbus_find_recursive().
Re commit 1395af6f ("qdev: add a maximum device allowed field for the
bus."), could someone please explain:
(1) why the early termination due to max_index vs. max_dev merits an
error message -- both non-recursive call-sites print an error of their
own anyway,
(2) why the
max_dev != 0 &&
max_dev <= max_index &&
name != NULL
condition justifies traversal termination -- in general, a bus called
"foo", albeit full of devices, could allow some of those devices to be a
child bus. Let's call one such (direct) child bus "bar".
If we're looking for "bar", or for one of its descendants, the current
logic seems to stop the search early, at "foo".
I think "bus_class->max_dev" should be checked only when we're actually
trying to add the device to the bus. (In qdev_set_parent_bus() -->
bus_add_child().)
- bus_add_child() should check the limit and set an Error,
- qdev_set_parent_bus_nofail() would abort() if there's an Error,
- qdev_set_parent_bus() would change signature and propagate error,
- all callers would be converted to either the new _nofail() or the old
function with the new signature.
I can try to write the patch if there's consensus about what should happen.
Thoughts?
Thanks!
Laszlo
Hi,
I don't think I understand what is a traversal termination.
But, this was added to specify a maximum amount of device on a bus.
(for virtio-bus which can have only one device connected)
1 - When you explicitly set the bus in command line with bus=...and it
is full
it returns the error:
qemu-system-i386: --device virtio-net,bus=virtio-pci-bus.0: Bus
'virtio-pci-bus.0' not found
That's why I added the error.
2 - I understand what you mean, but does your idea allows us to connect
a device to the first
non-full bus?
Thanks,
Fred
