Eric Lee / linux-smarc-t335x-v3.2

Commit f702d7013c7470284843a6370aaa53b8b75c5a40

Authored by Eric W. Biederman 2006-06-29 17:25:02 +0800

Committed by Linus Torvalds 2006-06-30 01:26:25 +0800

Exists in master and in 4 other branches

[PATCH] genirq: irq: document what an IRQ is

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>

Showing 1 changed file with 22 additions and 0 deletions Side-by-side Diff

Documentation/IRQ.txt

Documentation/IRQ.txt

Diff comments View file @ f702d70

	1	+What is an IRQ?
	2	+
	3	+An IRQ is an interrupt request from a device.
	4	+Currently they can come in over a pin, or over a packet.
	5	+Several devices may be connected to the same pin thus
	6	+sharing an IRQ.
	7	+
	8	+An IRQ number is a kernel identifier used to talk about a hardware
	9	+interrupt source. Typically this is an index into the global irq_desc
	10	+array, but except for what linux/interrupt.h implements the details
	11	+are architecture specific.
	12	+
	13	+An IRQ number is an enumeration of the possible interrupt sources on a
	14	+machine. Typically what is enumerated is the number of input pins on
	15	+all of the interrupt controller in the system. In the case of ISA
	16	+what is enumerated are the 16 input pins on the two i8259 interrupt
	17	+controllers.
	18	+
	19	+Architectures can assign additional meaning to the IRQ numbers, and
	20	+are encouraged to in the case where there is any manual configuration
	21	+of the hardware involved. The ISA IRQs are a classic example of
	22	+assigning this kind of additional meaning.