What is the use of the interrupt flag IRQF_TRIGGER_NONE?

Question

can anyone explain the flag, IRQF_TRIGGER_NONE declared linux in the file,/kernel/linux/include/interrupt.h. How can one use this flag?

Answer 1

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.