HID: haptic: add hid_haptic_switch_mode

Function hid_haptic_switch_mode() can be used to switch between
device-controlled mode and host-controlled mode. Uploading a
WAVEFORMPRESS or WAVEFORMRELEASE effect triggers host-controlled mode if
the device is in device-controlled mode.

Signed-off-by: Angela Czubak <aczubak@google.com>
Co-developed-by: Jonathan Denose <jdenose@google.com>
Signed-off-by: Jonathan Denose <jdenose@google.com>
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>

Author: Angela Czubak

drivers/hid/hid-haptic.c

@@ -5,6 +5,7 @@
  *  Copyright (c) 2021 Angela Czubak <acz@semihalf.com>
  */
 
+#include <linux/input/mt.h>
 #include <linux/module.h>
 
 #include "hid-haptic.h"
@@ -197,12 +198,46 @@ static void fill_effect_buf(struct hid_haptic_device *haptic,
 	mutex_unlock(&haptic->manual_trigger_mutex);
 }
 
+static void switch_mode(struct hid_device *hdev, struct hid_haptic_device *haptic,
+			int mode)
+{
+	struct hid_report *rep = haptic->auto_trigger_report;
+	struct hid_field *field;
+	s32 value;
+	int i, j;
+
+	if (mode == HID_HAPTIC_MODE_HOST)
+		value = HID_HAPTIC_ORDINAL_WAVEFORMSTOP;
+	else
+		value = haptic->default_auto_trigger;
+
+	mutex_lock(&haptic->auto_trigger_mutex);
+	for (i = 0; i < rep->maxfield; i++) {
+		field = rep->field[i];
+		/* Ignore if report count is out of bounds. */
+		if (field->report_count < 1)
+			continue;
+
+		for (j = 0; j < field->maxusage; j++) {
+			if (field->usage[j].hid == HID_HP_AUTOTRIGGER)
+				field->value[j] = value;
+		}
+	}
+
+	/* send the report */
+	hid_hw_request(hdev, rep, HID_REQ_SET_REPORT);
+	mutex_unlock(&haptic->auto_trigger_mutex);
+	haptic->mode = mode;
+}
+
 static int hid_haptic_upload_effect(struct input_dev *dev, struct ff_effect *effect,
 				    struct ff_effect *old)
 {
+	struct hid_device *hdev = input_get_drvdata(dev);
 	struct ff_device *ff = dev->ff;
 	struct hid_haptic_device *haptic = ff->private;
 	int i, ordinal = 0;
+	bool switch_modes = false;
 
 	/* If vendor range, check vendor id and page */
 	if (effect->u.haptic.hid_usage >= (HID_HP_VENDORWAVEFORMMIN & HID_USAGE) &&
@@ -225,6 +260,16 @@ static int hid_haptic_upload_effect(struct input_dev *dev, struct ff_effect *eff
 	fill_effect_buf(haptic, &effect->u.haptic, &haptic->effect[effect->id],
 			ordinal);
 
+	if (effect->u.haptic.hid_usage == (HID_HP_WAVEFORMPRESS & HID_USAGE) ||
+			effect->u.haptic.hid_usage == (HID_HP_WAVEFORMRELEASE & HID_USAGE))
+		switch_modes = true;
+
+	/* If device is in autonomous mode, and the uploaded effect signals userspace
+	 * wants control of the device, change modes
+	 */
+	if (switch_modes && haptic->mode == HID_HAPTIC_MODE_DEVICE)
+		switch_mode(hdev, haptic, HID_HAPTIC_MODE_HOST);
+
 	return 0;
 }
 
@@ -290,27 +335,33 @@ static void effect_set_default(struct ff_effect *effect)
 static int hid_haptic_erase(struct input_dev *dev, int effect_id)
 {
 	struct hid_haptic_device *haptic = dev->ff->private;
+	struct hid_device *hdev = input_get_drvdata(dev);
 	struct ff_effect effect;
 	int ordinal;
 
 	effect_set_default(&effect);
 
 	if (effect.u.haptic.hid_usage == (HID_HP_WAVEFORMRELEASE & HID_USAGE)) {
 		ordinal = haptic->release_ordinal;
-		if (!ordinal)
+		if (!ordinal) {
 			ordinal = HID_HAPTIC_ORDINAL_WAVEFORMNONE;
-		else
-			effect.u.haptic.hid_usage = HID_HP_WAVEFORMRELEASE &
-				HID_USAGE;
+			if (haptic->mode == HID_HAPTIC_MODE_HOST)
+				switch_mode(hdev, haptic, HID_HAPTIC_MODE_DEVICE);
+		} else
+			effect.u.haptic.hid_usage = HID_HP_WAVEFORMRELEASE & HID_USAGE;
+
 		fill_effect_buf(haptic, &effect.u.haptic, &haptic->effect[effect_id],
 				ordinal);
 	} else if (effect.u.haptic.hid_usage == (HID_HP_WAVEFORMPRESS & HID_USAGE)) {
 		ordinal = haptic->press_ordinal;
-		if (!ordinal)
+		if (!ordinal) {
 			ordinal = HID_HAPTIC_ORDINAL_WAVEFORMNONE;
+			if (haptic->mode == HID_HAPTIC_MODE_HOST)
+				switch_mode(hdev, haptic, HID_HAPTIC_MODE_DEVICE);
+		}
 		else
-			effect.u.haptic.hid_usage = HID_HP_WAVEFORMPRESS &
-				HID_USAGE;
+			effect.u.haptic.hid_usage = HID_HP_WAVEFORMPRESS & HID_USAGE;
+
 		fill_effect_buf(haptic, &effect.u.haptic, &haptic->effect[effect_id],
 				ordinal);
 	}
@@ -392,6 +443,7 @@ int hid_haptic_init(struct hid_device *hdev,
 	haptic->hid_usage_map[HID_HAPTIC_ORDINAL_WAVEFORMSTOP] =
 		HID_HP_WAVEFORMSTOP & HID_USAGE;
 
+	mutex_init(&haptic->auto_trigger_mutex);
 	for (r = 0; r < haptic->auto_trigger_report->maxfield; r++)
 		parse_auto_trigger_field(haptic, haptic->auto_trigger_report->field[r]);