HID: wacom: Replace magic masks and comparisons with switch cases

Reasoning through the conditions under which a particular block of code
in 'wacom_intuos_general' will be reached is not at all easy due to the
sheer number of magic masks and comparisons. Remove these and replace
them with a switch statement over the various 'types' of packets that
will be encountered.
Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/wacom_wac.c

@@ -886,6 +886,7 @@ static int wacom_intuos_general(struct wacom_wac *wacom)
 	unsigned char *data = wacom->data;
 	struct input_dev *input = wacom->pen_input;
 	int idx = (features->type == INTUOS) ? (data[1] & 0x01) : 0;
+	unsigned char type = (data[1] >> 1) & 0x0F;
 	unsigned int t;
 
 	if (data[0] != WACOM_REPORT_PENABLED && data[0] != WACOM_REPORT_CINTIQ &&
@@ -902,8 +903,12 @@ static int wacom_intuos_general(struct wacom_wac *wacom)
 		input_report_abs(input, ABS_DISTANCE, ((data[9] >> 3) & 0x1f));
 	}
 
+	switch (type) {
+	case 0x00:
+	case 0x01:
+	case 0x02:
+	case 0x03:
 		/* general pen packet */
-	if ((data[1] & 0xb8) == 0xa0) {
 		t = (data[6] << 2) | ((data[7] >> 6) & 3);
 		if (features->pressure_max == 2047) {
 			t = (t << 1) | (data[1] & 1);
@@ -917,21 +922,20 @@ static int wacom_intuos_general(struct wacom_wac *wacom)
 		input_report_key(input, BTN_STYLUS, data[1] & 2);
 		input_report_key(input, BTN_STYLUS2, data[1] & 4);
 		input_report_key(input, BTN_TOUCH, t > 10);
-	}
+		break;
 
+	case 0x0a:
+	case 0x0b:
 		/* airbrush second packet */
-	if ((data[1] & 0xbc) == 0xb4) {
 		input_report_abs(input, ABS_WHEEL,
 				(data[6] << 2) | ((data[7] >> 6) & 3));
 		input_report_abs(input, ABS_TILT_X,
 				 (((data[7] << 1) & 0x7e) | (data[8] >> 7)) - 64);
 		input_report_abs(input, ABS_TILT_Y, (data[8] & 0x7f) - 64);
-	}
-
-	/* 4D mouse, 2D mouse, marker pen rotation, tilt mouse, or Lens cursor packets */
-	if ((data[1] & 0xbc) == 0xa8 || (data[1] & 0xbe) == 0xb0 || (data[1] & 0xbc) == 0xac) {
+		break;
 
-		if (data[1] & 0x02) {
+	case 0x05:
+	case 0x07:
 		/* Rotation packet */
 		if (features->type >= INTUOS3S) {
 			/* I3 marker pen rotation */
@@ -945,8 +949,13 @@ static int wacom_intuos_general(struct wacom_wac *wacom)
 			input_report_abs(input, ABS_RZ, (data[7] & 0x20) ?
 				((t - 1) / 2) : -t / 2);
 		}
+		break;
 
-		} else if (!(data[1] & 0x10) && features->type < INTUOS3S) {
+	/* 4D mouse, 2D mouse, marker pen rotation, tilt mouse, or Lens cursor packets */
+	case 0x04:
+	case 0x06:
+	case 0x08:
+		if (features->type < INTUOS3S && type != 0x08) {
 			/* 4D mouse packet */
 			input_report_key(input, BTN_LEFT,   data[8] & 0x01);
 			input_report_key(input, BTN_MIDDLE, data[8] & 0x02);
@@ -956,8 +965,8 @@ static int wacom_intuos_general(struct wacom_wac *wacom)
 			input_report_key(input, BTN_EXTRA,  data[8] & 0x10);
 			t = (data[6] << 2) | ((data[7] >> 6) & 3);
 			input_report_abs(input, ABS_THROTTLE, (data[8] & 0x08) ? -t : t);
-
-		} else if (wacom->tool[idx] == BTN_TOOL_MOUSE) {
+		}
+		else if (wacom->tool[idx] == BTN_TOOL_MOUSE) {
 			/* I4 mouse */
 			if (features->type >= INTUOS4S && features->type <= INTUOSPL) {
 				input_report_key(input, BTN_LEFT,   data[6] & 0x01);
@@ -985,7 +994,8 @@ static int wacom_intuos_general(struct wacom_wac *wacom)
 					input_report_key(input, BTN_EXTRA,  data[8] & 0x20);
 				}
 			}
-		} else if ((features->type < INTUOS3S || features->type == INTUOS3L ||
+		}
+		else if ((features->type < INTUOS3S || features->type == INTUOS3L ||
 		          features->type == INTUOS4L || features->type == INTUOS5L ||
 		          features->type == INTUOSPL) &&
 		         wacom->tool[idx] == BTN_TOOL_LENS) {
@@ -996,6 +1006,15 @@ static int wacom_intuos_general(struct wacom_wac *wacom)
 			input_report_key(input, BTN_SIDE,   data[8] & 0x10);
 			input_report_key(input, BTN_EXTRA,  data[8] & 0x08);
 		}
+		break;
+
+	case 0x09:
+	case 0x0c:
+	case 0x0d:
+	case 0x0e:
+	case 0x0f:
+		/* unhandled */
+		break;
 	}
 
 	input_report_abs(input, ABS_MISC, wacom->id[idx]); /* report tool id */