Button callback: guru mediation if None

[fstengel]

Using the example main.py, I wanted to have button C stopping the various button polls. So I added, within button_handler_c:

a._user_callback=None

hoping that button A would stop answering polls. What I got was:

File "/flash/lib/input.py", line 53, in _callback
TypeError: 'NoneType' object is not callable
Guru Meditation Error: Core  1 panic'ed (Interrupt wdt timeout on CPU1)
Core 1 register dump:
PC      : 0x40093da6  PS      : 0x00060d34  A0      : 0x80092442  A1      : 0x3ffb8550  
A2      : 0x3ffc30d0  A3      : 0x3ffb8754  A4      : 0x00000001  A5      : 0x00000001  
A6      : 0x00060d23  A7      : 0x00000000  A8      : 0x3ffb8754  A9      : 0x3ffb8754  
A10     : 0x00000014  A11     : 0x00000014  A12     : 0x00000001  A13     : 0x00000001  
A14     : 0x00060d23  A15     : 0x00000000  SAR     : 0x0000000a  EXCCAUSE: 0x00000006  
EXCVADDR: 0x00000000  LBEG    : 0x4009b015  LEND    : 0x4009b025  LCOUNT  : 0xffffffff  

Backtrace: 0x40093da6:0x3ffb8550 0x4009243f:0x3ffb8570 0x40090790:0x3ffb8590 0x400d80d1:0x3ffb85d0 0x400e22fc:0x3ffb8600 0x400e26ab:0x3ffb8620 0x400d7c98:0x3ffb8660

Core 0 register dump:
PC      : 0x400916fe  PS      : 0x00060034  A0      : 0x80092103  A1      : 0x3ffb13a0  
A2      : 0x3ffb24c8  A3      : 0x0000cdcd  A4      : 0xb33fffff  A5      : 0x00000001  
A6      : 0x00060021  A7      : 0x0000abab  A8      : 0x0000abab  A9      : 0x3ffb13a0  
A10     : 0x00000003  A11     : 0x00060023  A12     : 0x00060021  A13     : 0x00000001  
A14     : 0x00060520  A15     : 0x00000000  SAR     : 0x0000001d  EXCCAUSE: 0x00000006  
EXCVADDR: 0x00000000  LBEG    : 0x00000000  LEND    : 0x00000000  LCOUNT  : 0x00000000  

Backtrace: 0x400916fe:0x3ffb13a0 0x40092100:0x3ffb13d0 0x40090a2b:0x3ffb13f0 0x400932cd:0x3ffb1410 0x40084cd6:0x3ffb1420 0x400d6edf:0x00000000

CPU halted.

Basically: the code does not check whether _user_callback is set to None or not... So what one could do is just at the start of _callback (before disabling irqs) insert:

if self._user_callback is None:
    return