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author | Eric W. Biederman <ebiederman@xmission.com> | 2006-06-29 02:25:02 -0700 |
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committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-06-29 10:26:25 -0700 |
commit | f702d7013c7470284843a6370aaa53b8b75c5a40 (patch) | |
tree | 1989bc89230b8319b3e2007b6e6238cc2dcec415 /Documentation/IRQ.txt | |
parent | 98bb244b685eb2a297aa60fa2e5c0631f95828e1 (diff) | |
download | kernel_samsung_tuna-f702d7013c7470284843a6370aaa53b8b75c5a40.zip kernel_samsung_tuna-f702d7013c7470284843a6370aaa53b8b75c5a40.tar.gz kernel_samsung_tuna-f702d7013c7470284843a6370aaa53b8b75c5a40.tar.bz2 |
[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>
Diffstat (limited to 'Documentation/IRQ.txt')
-rw-r--r-- | Documentation/IRQ.txt | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/Documentation/IRQ.txt b/Documentation/IRQ.txt new file mode 100644 index 0000000..1011e71 --- /dev/null +++ b/Documentation/IRQ.txt @@ -0,0 +1,22 @@ +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. |