Hi Jason,
Jason Gerecke said the following on 09/28/2012 06:38 PM:
But trying to fix like that raised another issue, as touchstrips LED are
> inverted [3] on Cintiq, so what works in reality is:
>
> - First ring => /sys/bus/usb/devices/.../wacom_led/status_led0_select
> - Second ring => /sys/bus/usb/devices/.../wacom_led/status_led1_select
> - First touchstrip => /sys/bus/usb/devices/.../wacom_led/status_led1_select
> - Second touchstrip => /sys/bus/usb/devices/.../wacom_led/status_led0_select
>
Even that patch is wrong, unfortunately. As noted in both the kernel's
ABI docs and the libwacom datafiles, it should be as follows:
Intuos4 (only [left] ring): => status_led0_select
Intuos5 (only [left] ring): => status_led0_select
Cintiq 21UX2 (left strip): => status_led1_select
Cintiq 21UX2 (right strip): => status_led0_select
Cintiq 22HD (left strip) => NO LEDs
Cintiq 22HD (right strip) => NO LEDs
Cintiq 24HD (left ring): => status_led1_select
Cintiq 24HD (right ring): => status_led0_select
Cintiq 24HD touch (left ring): => status_led1_select
Cintiq 24HD touch (right ring): => status_led0_select
Though its not a/documented/ rule, the behavior can be summed up as
follows: if a device has only one ring/strip, use status_led0_select;
otherwise the left ring/strip is controlled by status_led1_select and
the right ring/strip by status_led0_select.
> But that patch was denied and the consensus reached was that such hardware
> implementation details should be hidden from userland apps
>
> So we need to fix the kernel to get:
>
> - First ring => /sys/bus/usb/devices/.../wacom_led/status_led0_select
> - Second ring => /sys/bus/usb/devices/.../wacom_led/status_led1_select
> - First touchstrip => /sys/bus/usb/devices/.../wacom_led/status_led0_select
> - Second touchstrip => /sys/bus/usb/devices/.../wacom_led/status_led1_select
>
> independently of the hardware.
>
I talked more with Ping yesterday, and I'm not sure if its something
that can really be fixed. The odd behavior is documented, which means
its not a bug. A fix then would fall under the category of kernel API
change, which can only be done for "grave errors or security problems"
(i.e., not bad API choice). Because the interface has been upstream
for a year now (almost to the day) which means there's likely
non-GNOME code out there using it -- "fixing" the kernel would thus
break existing applications.
The only real solution I see is to create a new API that makes more
sense, like what Przemo is trying to do for the OLEDs. Even that's not
a perfect solution (more maintenance work in the kernel), but its not
the quagmire that tweaking what already exists is.
So I am now rewriting the patch for GNOME bug 676558 [1] using the
logic above.
Reading g-s-d code, it is assumed that if there is only one ring, it's
on the left and if there are two, first one is on the left and second
one on the right [2]:
static GList *
gsd_wacom_device_add_ring_modes (...)
{
...
if ((direction & WACOM_BUTTON_POSITION_LEFT) &&
libwacom_has_ring (wacom_device)) {
...
} else if ((direction & WACOM_BUTTON_POSITION_RIGHT) &&
libwacom_has_ring2 (wacom_device)) {
...
}
...
}
Same for strip, if there's only one it is assumed to be on the left
whereas if there are two, the first one is on the left and second one
on the right [3]:
static GList *
gsd_wacom_device_add_strip_modes (...)
{
...
if ((direction & WACOM_BUTTON_POSITION_LEFT) && num_strips >=
1) {
....
} else if ((direction & WACOM_BUTTON_POSITION_RIGHT) &&
num_strips >= 2) {
....
}
....
}
Can you confirm if that's always the case? libwacom API does not seem
particularly clear on this.
Cheers,
Olivier
--
[1] https://bugzilla.gnome.org/show_bug.cgi?id=676558
[2]
http://git.gnome.org/browse/gnome-settings-daemon/tree/plugins/wacom/gsd-wacom-device.c#n996
[3]
http://git.gnome.org/browse/gnome-settings-daemon/tree/plugins/wacom/gsd-wacom-device.c#n1031
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