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- 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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