On Thu, 5 Jan 2017, Benjamin Tissoires wrote:

For case 1, the hiddev documentation provides an ioctl to do the
init manually. A solution could be to retrieve the requested report
when EVIOCGUSAGE is called, in the same way hidraw does. I would be
tempted to not change the behavior and hope that we won't break any
userspace tool.

I'd like to be applying the HID_QUIRK_NO_INIT_REPORTS removal as soon as 
possible so that it gets exposure in linux-next over the whole development 
cycle.

I am however too conservative to ignore the potential hiddev breakage, I 
am afraid. This has a real potential of breaking systems, and 
administrators having hard time figuring out of happened; essentialy, this 
is userspace-visible behavior change (regression) for which we haven't 
done any long-term depreciation (such as printing a warning "please talk 
to your hiddev driver vendor" in case the driver seems to assume 
initialized reports) at least for a few years.

I think that either doing it at a connect time, or during first 
EVIOCGUSAGE ioctl() call is a must.

Otherwise, I'd be super-happy to finally get rid of this giant PITA.

Thanks!

-- 
Jiri Kosina
SUSE Labs