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

["Kaustabh Chakraborty" <kauschluss@disroot.org>]

On 2026-07-24 12:24 -07:00, Dmitry Torokhov wrote:
> Hi Kaustabh,
>
> On Fri, Jul 24, 2026 at 12:54:04AM +0530, Kaustabh Chakraborty wrote:
>> 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
>> scren, 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.
>
> This makes the check basically a no-op as SUB_BIT_EXIST would always be
> set when we reach this function. It may very well be that we want to
> delete this check altogether, or maybe we need to add SUB_BIT_UPDATE and
> SUB_BIT_WAIT. I am curious what status bits you see when this condition
> (original) triggers for you...

I see 0x03 [EXIST | DOWN] when the finger touches the screen, and 0x05
[EXIST | MOVE] when it moves. When it stays in the same place (this is
triggered in multitouch where one finger moves generating an event but
the other is stagnant) it reports 0x01 [EXIST]. When it's lifted up it
reports 0x08 [UP].

It looks like report_finger() is meant to be called when the finger is
up but it isn't because EXIST is not set during the UP event. So I guess
the solution is to remove the guard in the IRQ func and call
report_finger() unconditionally.

>> 
>> Signed-off-by: Kaustabh Chakraborty <kauschluss@disroot.org>
>> ---
>>  drivers/input/touchscreen/zinitix.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/drivers/input/touchscreen/zinitix.c b/drivers/input/touchscreen/zinitix.c
>> index 3421b8ffb19b..fdcb80f52c91 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;
>> 
>
> Thanks.