Revision b31a3bc3dbd2f42b61674d37de7f46022e1f6846 authored by Linus Torvalds on 19 March 2016, 23:09:43 UTC, committed by Linus Torvalds on 19 March 2016, 23:09:43 UTC
Pull arch/sh updates from Rich Felker: "This includes minor cleanups, a fix for a crash that likely affects all sh models with MMU, and introduction of a framework for boards described by device tree, which sets the stage for future J2 support" * tag 'tag-sh-for-4.6' of git://git.libc.org/linux-sh: sched/preempt, sh: kmap_coherent relies on disabled preemption sh: add SMP method selection to device tree pseudo-board sh: add device tree support and generic board using device tree sh: remove arch-specific localtimer and use generic one sh: make MMU-specific SMP code conditional on CONFIG_MMU sh: provide unified syscall trap compatible with all SH models sh: New gcc support sh: Disable trace for kernel uncompressing. sh: Use generic clkdev.h header
IRQ.txt
What is an IRQ?
An IRQ is an interrupt request from a device.
Currently they can come in over a pin, or over a packet.
Several devices may be connected to the same pin thus
sharing an IRQ.
An IRQ number is a kernel identifier used to talk about a hardware
interrupt source. Typically this is an index into the global irq_desc
array, but except for what linux/interrupt.h implements the details
are architecture specific.
An IRQ number is an enumeration of the possible interrupt sources on a
machine. Typically what is enumerated is the number of input pins on
all of the interrupt controller in the system. In the case of ISA
what is enumerated are the 16 input pins on the two i8259 interrupt
controllers.
Architectures can assign additional meaning to the IRQ numbers, and
are encouraged to in the case where there is any manual configuration
of the hardware involved. The ISA IRQs are a classic example of
assigning this kind of additional meaning.
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