The UHID_{START,STOP,OPEN,CLOSE} events should be ignored by us to avoid
triggering the warn(). It is safe to do that. Add few comments that
explain why we don't have to handle these.
---
profiles/input/hog.c | 32 +++++++++++++++++++++++++++++++-
1 file changed, 31 insertions(+), 1 deletion(-)
diff --git a/profiles/input/hog.c b/profiles/input/hog.c
index 91c2802..0130f94 100644
--- a/profiles/input/hog.c
+++ b/profiles/input/hog.c
@@ -621,12 +621,42 @@ static gboolean uhid_event_cb(GIOChannel *io, GIOCondition cond,
DBG("uHID event type %d received", ev.type);
switch (ev.type) {
+ case UHID_START:
+ case UHID_STOP:
+ /* These are called to start and stop the underlying hardware.
+ * For HoG we open the channels before creating the device so
+ * the hardware is always ready. No need to handle these.
+ * Note that these are also called when the kernel switches
+ * between device-drivers loaded on the HID device. But we can
+ * simply keep the hardware alive during transitions and it
+ * works just fine.
+ * The kernel never destroys a device itself! Only an explicit
+ * UHID_DESTROY request can remove a device. */
+ break;
+ case UHID_OPEN:
+ case UHID_CLOSE:
+ /* OPEN/CLOSE are sent whenever user-space opens any interface
+ * provided by the kernel HID device. Whenever the open-count
+ * is non-zero we must be ready for I/O. As long as it is zero,
+ * we can decide to drop all I/O and put the device asleep. This
+ * is optional, though. Moreover, some special device drivers
+ * are buggy in that regard, so maybe we just keep I/O always
+ * awake like HIDP in the kernel does. */
+ break;
case UHID_OUTPUT:
case UHID_FEATURE:
forward_report(hogdev, &ev);
break;
case UHID_OUTPUT_EV:
- DBG("uHID output event: type %d code %d value %d",
+ /* This is only sent by kernels prior to linux-3.11. It requires
+ * us to parse HID-descriptors in user-space to properly handle
+ * it. This is redundant as the kernel does it already. That's
+ * why newer kernels assemble the output-reports and send it to
+ * us via UHID_OUTPUT.
+ * We never implemented this, so we rely on users to use
+ * recent-enough kernels if they want this feature. No reason to
+ * implement this for older kernels. */
+ DBG("Unsupported uHID output event: type %d code %d value %d",
ev.u.output_ev.type, ev.u.output_ev.code,
ev.u.output_ev.value);
break;
--
1.8.4
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