2 files changed, 33 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:
diff --git a/include/linux/hid.h b/include/linux/hid.h
index 8da3e1f48195..0267aa5c1ea3 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -345,6 +345,7 @@ struct hid_item {
 #define HID_QUIRK_SKIP_OUTPUT_REPORT_ID         BIT(17)
 #define HID_QUIRK_NO_OUTPUT_REPORTS_ON_INTR_EP  BIT(18)
 #define HID_QUIRK_HAVE_SPECIAL_DRIVER           BIT(19)
+#define HID_QUIRK_INCREMENT_USAGE_ON_DUPLICATE  BIT(20)
 #define HID_QUIRK_FULLSPEED_INTERVAL            BIT(28)
 #define HID_QUIRK_NO_INIT_REPORTS               BIT(29)
 #define HID_QUIRK_NO_IGNORE                     BIT(30)
@@ -502,6 +503,7 @@ struct hid_output_fifo {
 
 #define HID_STAT_ADDED          BIT(0)
 #define HID_STAT_PARSED         BIT(1)
+#define HID_STAT_DUP_DETECTED   BIT(2)
 
 struct hid_input {
         struct list_head list;