Re: [PATCH v3 02/49] Input: introduce input_mt_report_slot_inactive

[Jiada Wang]

Hi Henrik


On 2019/09/18 3:25, Henrik Rydberg wrote:
> Hi Jiada,
>
> > input_mt_report_slot_state() ignores the tool when the slot is closed.
> > which has caused a bit of confusion.
> > This patch introduces input_mt_report_slot_inactive() to report slot
> > inactive state.
> > replaces all input_mt_report_slot_state() with
> > input_mt_report_slot_inactive() in case of close of slot.
>
> This patch looks very odd, I am afraid.
>
> When a driver needs to use input_mt functions, it first calls 
> input_mt_init_slots() during setup. The MT state then remains in effect 
> until the driver is destroyed. Thus, there is no valid case when 
> input_mt_report_slot_state() would fail to execute the line
>
>  ÂÂ input_event(dev, EV_ABS, ABS_MT_TRACKING_ID, -1)
>
> when active == false.
>
> What input_mt_report_slot_state() does do, however, is to ignore the 
> event when no MT state has been set, which does happen for some drivers 
> handling both normal and MT devices. Changing such a driver in the way 
> you suggest would introduce new events in existing, working cases, and 
> possibly break userspace. We should try very hard to avoid it.

thanks for your comment,

Just to make sure, I think your comment is for
patch "[PATCH v3 01/49] Input: switch to use return value of 
input_mt_report_slot_state"
not for "[PATCH v3 02/49] Input: introduce 
input_mt_report_slot_inactive", right?

yes, I agree
by having change:

-    input_mt_report_slot_state(dev, tool_type, active);
-    if (active) {
+        if (input_mt_report_slot_state(dev, tool_type, active)){
             ... ...
     }

the logic of the driver is changed, when (mt == NULL && active == true).
I will drop patch "Input: switch to use return value of" in next version

Thanks,
Jiada

> Thanks,
>
> Henrik