[PATCH v3 2/5] Input: zinitix - do not ignore non-moving fingers

[Kaustabh Chakraborty <kauschluss@disroot.org>]

With the ZT7548 touchscreen present in the Galaxy J6, multitouch does not
work reliably. This is due to the fact that the driver reports fingers
only when their state is changed, so it's either placed against the
screen, moved, or drawn away from the screen.

The function which is responsible for this is zinitix_report_finger().
This function is called from the IRQ handler, under the following
condition:

		if (p->sub_status & SUB_BIT_EXIST)
			zinitix_report_finger(bt541, i, p);

This implies and ensures that every valid finger must have the
SUB_BIT_EXIST flag.

However, at the beginning of the function, it refuses to recognize any
finger if it has none of SUB_BIT_UP | SUB_BIT_DOWN | SUB_BIT_MOVE. This
excludes fingers in reports which do not move from the position since
the previous interrupt. Add SUB_BIT_EXIST to the list of valid bits.

Signed-off-by: Kaustabh Chakraborty <kauschluss@disroot.org>
---
 drivers/input/touchscreen/zinitix.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/input/touchscreen/zinitix.c b/drivers/input/touchscreen/zinitix.c
index 3421b8ffb19b..a0a89d25e25b 100644
--- a/drivers/input/touchscreen/zinitix.c
+++ b/drivers/input/touchscreen/zinitix.c
@@ -406,7 +406,7 @@ static void zinitix_report_finger(struct bt541_ts_data *bt541, int slot,
 	u16 x, y;
 
 	if (unlikely(!(p->sub_status &
-		       (SUB_BIT_UP | SUB_BIT_DOWN | SUB_BIT_MOVE)))) {
+		       (SUB_BIT_EXIST | SUB_BIT_UP | SUB_BIT_DOWN | SUB_BIT_MOVE)))) {
 		dev_dbg(&bt541->client->dev, "unknown finger event %#02x\n",
 			p->sub_status);
 		return;
@@ -473,7 +473,7 @@ static irqreturn_t zinitix_ts_irq_handler(int irq, void *bt541_handler)
 		const struct point_coord *p = &touch_event.point_coord[i];
 
 		/* Only process contacts that are actually reported */
-		if (p->sub_status & SUB_BIT_EXIST)
+		if (p->sub_status)
 			zinitix_report_finger(bt541, i, p);
 	}
 

-- 
2.54.0