HID: wacom: Queue events with missing type/serial data for later processing

Userspace expects to receive tool type and serial number information
for the active pen in the very first kernel report, if such data is
supported by the hardware. While this expectation is not an issue for
EMR devices, AES sensors will often send several packets worth of in-
range data before relaying type/serial data to the kernel. Sending this
data "late" can result in proximity-tracking issues by xf86-input-wacom,
or an inability to distinguish different pens by input-wacom.

Options for dealing with this situation include ignoring reports from
the tablet until we get the necessary data, or using the information
from the last-seen pen instead of the (eventual) real data. Neither
option is particularly attractive: the former results in truncated
strokes and the latter causes issues with switching between pens.

This commit instead opts to queue up events with missing information
until we receive a report which contains it. At that point, we can
update the driver's state variables (id[0] and serial[0]) and replay
the queued events.
Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/wacom_sys.c

@@ -56,6 +56,107 @@ static int wacom_set_report(struct hid_device *hdev, u8 type, u8 *buf,
 	return retval;
 }
 
+static void wacom_wac_queue_insert(struct hid_device *hdev,
+				   struct kfifo_rec_ptr_2 *fifo,
+				   u8 *raw_data, int size)
+{
+	bool warned = false;
+
+	while (kfifo_avail(fifo) < size) {
+		if (!warned)
+			hid_warn(hdev, "%s: kfifo has filled, starting to drop events\n", __func__);
+		warned = true;
+
+		kfifo_skip(fifo);
+	}
+
+	kfifo_in(fifo, raw_data, size);
+}
+
+static void wacom_wac_queue_flush(struct hid_device *hdev,
+				  struct kfifo_rec_ptr_2 *fifo)
+{
+	while (!kfifo_is_empty(fifo)) {
+		u8 buf[WACOM_PKGLEN_MAX];
+		int size;
+		int err;
+
+		size = kfifo_out(fifo, buf, sizeof(buf));
+		err = hid_report_raw_event(hdev, HID_INPUT_REPORT, buf, size, false);
+		if (err) {
+			hid_warn(hdev, "%s: unable to flush event due to error %d\n",
+				 __func__, err);
+		}
+	}
+}
+
+static int wacom_wac_pen_serial_enforce(struct hid_device *hdev,
+		struct hid_report *report, u8 *raw_data, int size)
+{
+	struct wacom *wacom = hid_get_drvdata(hdev);
+	struct wacom_wac *wacom_wac = &wacom->wacom_wac;
+	struct wacom_features *features = &wacom_wac->features;
+	bool flush = false;
+	bool insert = false;
+	int i, j;
+
+	if (wacom_wac->serial[0] || !(features->quirks & WACOM_QUIRK_TOOLSERIAL))
+		return 0;
+
+	/* Queue events which have invalid tool type or serial number */
+	for (i = 0; i < report->maxfield; i++) {
+		for (j = 0; j < report->field[i]->maxusage; j++) {
+			struct hid_field *field = report->field[i];
+			struct hid_usage *usage = &field->usage[j];
+			unsigned int equivalent_usage = wacom_equivalent_usage(usage->hid);
+			unsigned int offset;
+			unsigned int size;
+			unsigned int value;
+
+			if (equivalent_usage != HID_DG_INRANGE &&
+			    equivalent_usage != HID_DG_TOOLSERIALNUMBER &&
+			    equivalent_usage != WACOM_HID_WD_SERIALHI &&
+			    equivalent_usage != WACOM_HID_WD_TOOLTYPE)
+				continue;
+
+			offset = field->report_offset;
+			size = field->report_size;
+			value = hid_field_extract(hdev, raw_data+1, offset + j * size, size);
+
+			/* If we go out of range, we need to flush the queue ASAP */
+			if (equivalent_usage == HID_DG_INRANGE)
+				value = !value;
+
+			if (value) {
+				flush = true;
+				switch (equivalent_usage) {
+				case HID_DG_TOOLSERIALNUMBER:
+					wacom_wac->serial[0] = value;
+					break;
+
+				case WACOM_HID_WD_SERIALHI:
+					wacom_wac->serial[0] |= ((__u64)value) << 32;
+					break;
+
+				case WACOM_HID_WD_TOOLTYPE:
+					wacom_wac->id[0] = value;
+					break;
+				}
+			}
+			else {
+				insert = true;
+			}
+		}
+	}
+
+	if (flush)
+		wacom_wac_queue_flush(hdev, &wacom_wac->pen_fifo);
+	else if (insert)
+		wacom_wac_queue_insert(hdev, &wacom_wac->pen_fifo, raw_data, size);
+
+	return insert && !flush;
+}
+
 static int wacom_raw_event(struct hid_device *hdev, struct hid_report *report,
 		u8 *raw_data, int size)
 {
@@ -64,6 +165,9 @@ static int wacom_raw_event(struct hid_device *hdev, struct hid_report *report,
 	if (size > WACOM_PKGLEN_MAX)
 		return 1;
 
+	if (wacom_wac_pen_serial_enforce(hdev, report, raw_data, size))
+		return -1;
+
 	memcpy(wacom->wacom_wac.data, raw_data, size);
 
 	wacom_wac_irq(&wacom->wacom_wac, size);
@@ -2580,6 +2684,10 @@ static int wacom_probe(struct hid_device *hdev,
 		goto fail;
 	}
 
+	error = kfifo_alloc(&wacom_wac->pen_fifo, WACOM_PKGLEN_MAX, GFP_KERNEL);
+	if (error)
+		goto fail;
+
 	wacom_wac->hid_data.inputmode = -1;
 	wacom_wac->mode_report = -1;
 
@@ -2643,6 +2751,8 @@ static void wacom_remove(struct hid_device *hdev)
 	if (wacom->wacom_wac.features.type != REMOTE)
 		wacom_release_resources(wacom);
 
+	kfifo_free(&wacom_wac->pen_fifo);
+
 	hid_set_drvdata(hdev, NULL);
 }
 

drivers/hid/wacom_wac.c

@@ -2085,6 +2085,7 @@ static void wacom_wac_pen_usage_mapping(struct hid_device *hdev,
 		wacom_map_usage(input, usage, field, EV_KEY, BTN_STYLUS2, 0);
 		break;
 	case HID_DG_TOOLSERIALNUMBER:
+		features->quirks |= WACOM_QUIRK_TOOLSERIAL;
 		wacom_map_usage(input, usage, field, EV_MSC, MSC_SERIAL, 0);
 
 		/* Adjust AES usages to match modern convention */

drivers/hid/wacom_wac.h

@@ -11,6 +11,7 @@
 
 #include <linux/types.h>
 #include <linux/hid.h>
+#include <linux/kfifo.h>
 
 /* maximum packet length for USB/BT devices */
 #define WACOM_PKGLEN_MAX	361
@@ -88,6 +89,7 @@
 #define WACOM_QUIRK_SENSE		0x0002
 #define WACOM_QUIRK_AESPEN		0x0004
 #define WACOM_QUIRK_BATTERY		0x0008
+#define WACOM_QUIRK_TOOLSERIAL		0x0010
 
 /* device types */
 #define WACOM_DEVICETYPE_NONE           0x0000
@@ -339,6 +341,7 @@ struct wacom_wac {
 	struct input_dev *pen_input;
 	struct input_dev *touch_input;
 	struct input_dev *pad_input;
+	struct kfifo_rec_ptr_2 pen_fifo;
 	int pid;
 	int num_contacts_left;
 	u8 bt_features;