On Thu, Sep 09, 2004 at 12:35:29PM +0530, Dhiman, Gaurav wrote: > In kernel source where can I find the code which actually identifies the > IRQ number by reading the APIC mask and status registers. If you are talking about the Intel architecture, no registers have to be read in order to determine the IRQ number. Every interrupt has an appropriate gate, which is initialized in arch/i386/kernel/i8259.c or arch/i386/kernel/io_apic.c. In order to understand interrupt handling would suggest studying the kernel sources and the appropriate reference manual of your architecture. Regards, Clemens -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/