On Wed, Oct 12, 2011 at 05:59:05PM +0100, Matthew Garrett wrote:
> On Wed, Oct 12, 2011 at 06:56:32PM +0200, Oliver Neukum wrote:
> > Am Mittwoch, 12. Oktober 2011, 18:16:51 schrieb Matthew Garrett:
> > > Yeah. Plausibly the model we have in hid is wrong at the moment - rather
> > > than set flags that block suspend, it might make more sense to take
> > > references. It'd complicate things a little, in that we'd have to take
> > > more care in terms of keeping track of the state.
> >
> > I am afraid references are very hard to take there because it needs to be done
> > in interrupt.
>
> True. That makes things rather more awkward.
I was looking at usb_autopm_get_interface_no_resume() yesterday for
the same reason, it seemed light-weight enough. No?
Btw, I wonder if the patch below would make sense or if calling put*()
is always a bug at zero usage count.
diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
index 34e3da5..4857e76 100644
--- a/drivers/usb/core/driver.c
+++ b/drivers/usb/core/driver.c
@@ -1516,7 +1516,7 @@ void usb_autopm_put_interface_no_suspend(struct usb_interface *intf)
struct usb_device *udev = interface_to_usbdev(intf);
usb_mark_last_busy(udev);
- atomic_dec(&intf->pm_usage_cnt);
+ atomic_add_unless(&intf->pm_usage_cnt, -1, 0);
pm_runtime_put_noidle(&intf->dev);
}
EXPORT_SYMBOL_GPL(usb_autopm_put_interface_no_suspend);
Henrik
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