Input: alps - only set fields that are actually present

Pinnacle / Rushmore packets contain either position info, or bitmap info,
never both. So far we've in essence been storing garbage in the position /
bitmap fields of the fields struct when decoding a bitmap / pos packet.

We've been relying on the following sequence to get away with this:

1) Decode bitmap packet
2) Process bitmap packet
3) Decode position packet
4) Use position / button info

This patch allows us to change this sequence, which will allow using the
position info when processing the bitmap for more accurate results.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/mouse/alps.c

@@ -576,6 +576,7 @@ static int alps_decode_pinnacle(struct alps_fields *f, unsigned char *p,
 	f->first_mp = !!(p[4] & 0x40);
 	f->is_mp = !!(p[0] & 0x40);
 
+	if (f->is_mp) {
 		f->fingers = (p[5] & 0x3) + 1;
 		f->x_map = ((p[4] & 0x7e) << 8) |
 			   ((p[1] & 0x7f) << 2) |
@@ -583,13 +584,14 @@ static int alps_decode_pinnacle(struct alps_fields *f, unsigned char *p,
 		f->y_map = ((p[3] & 0x70) << 4) |
 			   ((p[2] & 0x7f) << 1) |
 			   (p[4] & 0x01);
-
+	} else {
 		f->st.x = ((p[1] & 0x7f) << 4) | ((p[4] & 0x30) >> 2) |
 		       ((p[0] & 0x30) >> 4);
 		f->st.y = ((p[2] & 0x7f) << 4) | (p[4] & 0x0f);
 		f->pressure = p[5] & 0x7f;
 
 		alps_decode_buttons_v3(f, p);
+	}
 
 	return 0;
 }
@@ -600,6 +602,7 @@ static int alps_decode_rushmore(struct alps_fields *f, unsigned char *p,
 	f->first_mp = !!(p[4] & 0x40);
 	f->is_mp = !!(p[5] & 0x40);
 
+	if (f->is_mp) {
 		f->fingers = max((p[5] & 0x3), ((p[5] >> 2) & 0x3)) + 1;
 		f->x_map = ((p[5] & 0x10) << 11) |
 			   ((p[4] & 0x7e) << 8) |
@@ -609,13 +612,14 @@ static int alps_decode_rushmore(struct alps_fields *f, unsigned char *p,
 			   ((p[3] & 0x70) << 4) |
 			   ((p[2] & 0x7f) << 1) |
 			   (p[4] & 0x01);
-
+	} else {
 		f->st.x = ((p[1] & 0x7f) << 4) | ((p[4] & 0x30) >> 2) |
 		       ((p[0] & 0x30) >> 4);
 		f->st.y = ((p[2] & 0x7f) << 4) | (p[4] & 0x0f);
 		f->pressure = p[5] & 0x7f;
 
 		alps_decode_buttons_v3(f, p);
+	}
 
 	return 0;
 }