IRQF_TRIGGER_NONE
is defined with a bit-mask of 0 indicating that it does NOT imply any kind of edge or level triggered interrupt behaviour.
#define IRQF_TRIGGER_NONE 0x00000000
Hence registering an ISR using request_irq()
with IRQF_TRIGGER_NONE
does NOT modify the existing configuration of the IRQ. This is important in scenarios where we would simply like to register an ISR for an hardware in the mode it is currently configured [1].
Example usage of IRQF_TRIGGER_NONE
in the Linux Kernel.