HID: input: don't register unmapped input devices

There is no need to register an input device containing no events.
This allows drivers using the quirk MULTI_INPUT to register one input
per report effectively used.

For backward compatibility, we need to add a quirk to request
this behavior.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

2 files changed, 78 insertions, 0 deletions

diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
index 21b196c394b1..945b8158ec4c 100644
--- a/drivers/hid/hid-input.c
+++ b/drivers/hid/hid-input.c
@@ -1198,6 +1198,67 @@ static struct hid_input *hidinput_allocate(struct hid_device *hid)
         return hidinput;
 }
 
+static bool hidinput_has_been_populated(struct hid_input *hidinput)
+{
+        int i;
+        unsigned long r = 0;
+
+        for (i = 0; i < BITS_TO_LONGS(EV_CNT); i++)
+                r |= hidinput->input->evbit[i];
+
+        for (i = 0; i < BITS_TO_LONGS(KEY_CNT); i++)
+                r |= hidinput->input->keybit[i];
+
+        for (i = 0; i < BITS_TO_LONGS(REL_CNT); i++)
+                r |= hidinput->input->relbit[i];
+
+        for (i = 0; i < BITS_TO_LONGS(ABS_CNT); i++)
+                r |= hidinput->input->absbit[i];
+
+        for (i = 0; i < BITS_TO_LONGS(MSC_CNT); i++)
+                r |= hidinput->input->mscbit[i];
+
+        for (i = 0; i < BITS_TO_LONGS(LED_CNT); i++)
+                r |= hidinput->input->ledbit[i];
+
+        for (i = 0; i < BITS_TO_LONGS(SND_CNT); i++)
+                r |= hidinput->input->sndbit[i];
+
+        for (i = 0; i < BITS_TO_LONGS(FF_CNT); i++)
+                r |= hidinput->input->ffbit[i];
+
+        for (i = 0; i < BITS_TO_LONGS(SW_CNT); i++)
+                r |= hidinput->input->swbit[i];
+
+        return !!r;
+}
+
+static void hidinput_cleanup_hidinput(struct hid_device *hid,
+                struct hid_input *hidinput)
+{
+        struct hid_report *report;
+        int i, k;
+
+        list_del(&hidinput->list);
+        input_free_device(hidinput->input);
+
+        for (k = HID_INPUT_REPORT; k <= HID_OUTPUT_REPORT; k++) {
+                if (k == HID_OUTPUT_REPORT &&
+                        hid->quirks & HID_QUIRK_SKIP_OUTPUT_REPORTS)
+                        continue;
+
+                list_for_each_entry(report, &hid->report_enum[k].report_list,
+                                    list) {
+
+                        for (i = 0; i < report->maxfield; i++)
+                                if (report->field[i]->hidinput == hidinput)
+                                        report->field[i]->hidinput = NULL;
+                }
+        }
+
+        kfree(hidinput);
+}
+
 /*
  * Register the input device; print a message.
  * Configure the input layer interface
@@ -1249,6 +1310,10 @@ int hidinput_connect(struct hid_device *hid, unsigned int force)
                                         hidinput_configure_usage(hidinput, report->field[i],
                                                                  report->field[i]->usage + j);
 
+                        if ((hid->quirks & HID_QUIRK_NO_EMPTY_INPUT) &&
+                            !hidinput_has_been_populated(hidinput))
+                                continue;
+
                         if (hid->quirks & HID_QUIRK_MULTI_INPUT) {
                                 /* This will leave hidinput NULL, so that it
                                  * allocates another one if we have more inputs on
@@ -1265,6 +1330,18 @@ int hidinput_connect(struct hid_device *hid, unsigned int force)
                 }
         }
 
+        if (hidinput && (hid->quirks & HID_QUIRK_NO_EMPTY_INPUT) &&
+            !hidinput_has_been_populated(hidinput)) {
+                /* no need to register an input device not populated */
+                hidinput_cleanup_hidinput(hid, hidinput);
+                hidinput = NULL;
+        }
+
+        if (list_empty(&hid->inputs)) {
+                hid_err(hid, "No inputs registered, leaving\n");
+                goto out_unwind;
+        }
+
         if (hidinput) {
                 if (drv->input_configured)
                         drv->input_configured(hid, hidinput);
diff --git a/include/linux/hid.h b/include/linux/hid.h
index 863744c38ddc..fffa06bc4880 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -282,6 +282,7 @@ struct hid_item {
 #define HID_QUIRK_BADPAD                        0x00000020
 #define HID_QUIRK_MULTI_INPUT                   0x00000040
 #define HID_QUIRK_HIDINPUT_FORCE                0x00000080
+#define HID_QUIRK_NO_EMPTY_INPUT                0x00000100
 #define HID_QUIRK_SKIP_OUTPUT_REPORTS           0x00010000
 #define HID_QUIRK_FULLSPEED_INTERVAL            0x10000000
 #define HID_QUIRK_NO_INIT_REPORTS               0x20000000