HID: handle cases of volume knobs generating relative values
There are some devices (for example Dell Multimedia Keyboard SK-8135) that have
a volume control knob which generates relative events instead of absolute.
hid-input maps them to ABS_VOLUME. HUT pages don't restrict volume to absolute
values.
Adding REL_VOLUME doesn't seem feasible, nothing knows how to handle it. This
patch translates relative ABS_VOLUME events into appropriate number of series
of VOLUME_UP or VOLUME_DOWN events respectively, so that userspace sees the
correct values in the end.
kernel.org bugzilla 5233
Reported-by: Jochen Eisinger <jochen@penguin-breeder.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
index 60de16a..bf7e307 100644
--- a/drivers/hid/hid-input.c
+++ b/drivers/hid/hid-input.c
@@ -882,6 +882,16 @@
field->dpad = usage->code;
}
+ /* for those devices which produce Consumer volume usage as relative,
+ * we emulate pressing volumeup/volumedown appropriate number of times
+ * in hidinput_hid_event()
+ */
+ if ((usage->type == EV_ABS) && (field->flags & HID_MAIN_ITEM_RELATIVE) &&
+ (usage->code == ABS_VOLUME)) {
+ set_bit(KEY_VOLUMEUP, input->keybit);
+ set_bit(KEY_VOLUMEDOWN, input->keybit);
+ }
+
hid_resolv_event(usage->type, usage->code);
#ifdef CONFIG_HID_DEBUG
printk("\n");
@@ -972,6 +982,21 @@
if ((usage->type == EV_KEY) && (usage->code == 0)) /* Key 0 is "unassigned", not KEY_UNKNOWN */
return;
+ if ((usage->type == EV_ABS) && (field->flags & HID_MAIN_ITEM_RELATIVE) &&
+ (usage->code == ABS_VOLUME)) {
+ int count = abs(value);
+ int direction = value > 0 ? KEY_VOLUMEUP : KEY_VOLUMEDOWN;
+ int i;
+
+ for (i = 0; i < count; i++) {
+ input_event(input, EV_KEY, direction, 1);
+ input_sync(input);
+ input_event(input, EV_KEY, direction, 0);
+ input_sync(input);
+ }
+ return;
+ }
+
input_event(input, usage->type, usage->code, value);
if ((field->flags & HID_MAIN_ITEM_RELATIVE) && (usage->type == EV_KEY))