Hi, While registering for an interrupt handler, we could specify IRQF_DISABLED flag to request_irq() to disable all other interrupts while the handler's execution, except the one that's being registered. I understand that this flag's usage is reserved only for performance-sensitive interrupts that needs to execute quickly and setting this for general (non-performance sensitive cases) use is considered bad. Qn.1: Is this the fast way of interrupt handling? Does this flag distinguish between fast and slow interrupts? Arm supports several processor modes that includes FIQ and Interrupt request mode. FIQ has higher priority over normal interrupt mode. Qn.2: Is FIQ mode supported by ARM is equivalent to doing IRQF_DISABLED in hardware? What is/are the significance/advantages of FIQ mode? Thanks & Regards, Rajasekhar