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-rw-r--r--drivers/hid/hid-input.c33
1 files changed, 31 insertions, 2 deletions
diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
index 6836a856c243..04056773102e 100644
--- a/drivers/hid/hid-input.c
+++ b/drivers/hid/hid-input.c
@@ -1100,8 +1100,31 @@ mapped:
 
 	set_bit(usage->type, input->evbit);
 
-	while (usage->code <= max && test_and_set_bit(usage->code, bit))
-		usage->code = find_next_zero_bit(bit, max + 1, usage->code);
+	/*
+	 * This part is *really* controversial:
+	 * - HID aims at being generic so we should do our best to export
+	 *   all incoming events
+	 * - HID describes what events are, so there is no reason for ABS_X
+	 *   to be mapped to ABS_Y
+	 * - HID is using *_MISC+N as a default value, but nothing prevents
+	 *   *_MISC+N to overwrite a legitimate even, which confuses userspace
+	 *   (for instance ABS_MISC + 7 is ABS_MT_SLOT, which has a different
+	 *   processing)
+	 *
+	 * If devices still want to use this (at their own risk), they will
+	 * have to use the quirk HID_QUIRK_INCREMENT_USAGE_ON_DUPLICATE, but
+	 * the default should be a reliable mapping.
+	 */
+	while (usage->code <= max && test_and_set_bit(usage->code, bit)) {
+		if (device->quirks & HID_QUIRK_INCREMENT_USAGE_ON_DUPLICATE) {
+			usage->code = find_next_zero_bit(bit,
+							 max + 1,
+							 usage->code);
+		} else {
+			device->status |= HID_STAT_DUP_DETECTED;
+			goto ignore;
+		}
+	}
 
 	if (usage->code > max)
 		goto ignore;
@@ -1611,6 +1634,8 @@ int hidinput_connect(struct hid_device *hid, unsigned int force)
 	INIT_LIST_HEAD(&hid->inputs);
 	INIT_WORK(&hid->led_work, hidinput_led_worker);
 
+	hid->status &= ~HID_STAT_DUP_DETECTED;
+
 	if (!force) {
 		for (i = 0; i < hid->maxcollection; i++) {
 			struct hid_collection *col = &hid->collection[i];
@@ -1677,6 +1702,10 @@ int hidinput_connect(struct hid_device *hid, unsigned int force)
 		goto out_unwind;
 	}
 
+	if (hid->status & HID_STAT_DUP_DETECTED)
+		hid_dbg(hid,
+			"Some usages could not be mapped, please use HID_QUIRK_INCREMENT_USAGE_ON_DUPLICATE if this is legitimate.\n");
+
 	return 0;
 
 out_unwind: