f702d7013c
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Rajesh Shah <rajesh.shah@intel.com> Cc: Andi Kleen <ak@muc.de> Cc: "Protasevich, Natalie" <Natalie.Protasevich@UNISYS.com> Cc: "Luck, Tony" <tony.luck@intel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
23 lines
962 B
Plaintext
23 lines
962 B
Plaintext
What is an IRQ?
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An IRQ is an interrupt request from a device.
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Currently they can come in over a pin, or over a packet.
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Several devices may be connected to the same pin thus
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sharing an IRQ.
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An IRQ number is a kernel identifier used to talk about a hardware
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interrupt source. Typically this is an index into the global irq_desc
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array, but except for what linux/interrupt.h implements the details
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are architecture specific.
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An IRQ number is an enumeration of the possible interrupt sources on a
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machine. Typically what is enumerated is the number of input pins on
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all of the interrupt controller in the system. In the case of ISA
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what is enumerated are the 16 input pins on the two i8259 interrupt
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controllers.
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Architectures can assign additional meaning to the IRQ numbers, and
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are encouraged to in the case where there is any manual configuration
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of the hardware involved. The ISA IRQs are a classic example of
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assigning this kind of additional meaning.
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