On Mon, 3 Dec 2012, Nestor Lopez Casado wrote:

quoted

quoted

It is clear that the goal is to make commit
4ea5454203d991ec85264f64f89ca8855fce69b0 less restrictive.
The problem is that this commit stops any communication with the
device, even configuration communication.

Logitech devices use their own protocol on top of the HID standard
protocol. For touch devices, this proprietary protocol requires to ask
the device for axis ranges, etc...

So here, the idea is not to open the can of worm for every hid devices
through hw_start() / hw_stop() calls, I think the idea of Andrew is
just to allow hid-logitech-dj to get rid of this restriction in some
particular circumstances.
Consider this as a controlled backdoor of the can of worms :)

I have been thinking for this for a while, and I wasn't able to come up
with anything I'd personally consider substantially better aproach than
splitting the lock. So I don't have strong objections at the very moment.

This will also allow us to get rid of what commit 596264082f introduced in
unifying driver, right? (adding Nestor to CC).

That is correct. Moreover, we are planning additional changes to
hid-logitech-dj that will somehow revert that commit. As Andrew
mentioned earlier, the drivers for Unifying devices need to query
several parameters during their probe() execution, and besides this
lock issue, there is still another problem with the current
hid-logitech-dj strategy.  Unifying devices can only be queried when
the radio link is active, and as such, we are planning to postpone
calling hid_add_device() until we are sure that the device has an
active radio link.

With both issues resolved, the path will be clear to add native
multitouch support for several Unifying devices like t650, t620 and
t400.

Nestor,

is there anything happening in this area, please?

-- 
Jiri Kosina
SUSE Labs