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bh=rgmi2nSM6UYOfDE5ZxkWJs6+gysmq8nIHaH1sQpiE4E=; b=gEbBBsQyC1gwckPXWAbDwwpwMzagecEG1N9kjZ102TFagmSPhfOYzQIT9gLyVv1kVRisPp TH9dKpt+oUUaJa/dyfIp7Lsv3i75/tkEoymFOqF86qcdDCoEg7mmxr4VleS4CLSI/wNfxk S6p/THnHWZmgLAYQvmZ3G9ZSjJoa3H7xOsjICf5erXGH6X/hQcSoWXGtsUE0eMmUwfqUFD fZzp/wcj1EknYPXqbwZ9AUcIOXX/UBZnP37WuUFifGn8QZSvqZnyPR5kgDM2nuqLu3GGUh 64z753zd9IwRez/K3kEtbkQoH9ts7DopE/8kO4DEYf5pUQQeNHBZ4M7LQ3vFoQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1746537615; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=rgmi2nSM6UYOfDE5ZxkWJs6+gysmq8nIHaH1sQpiE4E=; b=UA9kl3+mldeSMELxp9++KKCnVCrpxpNzQcnQOwsmtye+WoMFV80UQ9DRr4Hl+EQpu26h+2 /0FWObulPc9qicAg== From: "tip-bot2 for Jiri Slaby (SUSE)" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: irq/cleanups] Documentation: irq/concepts: Minor improvements Cc: "Jiri Slaby (SUSE)" , Thomas Gleixner , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20250319092951.37667-55-jirislaby@kernel.org> References: <20250319092951.37667-55-jirislaby@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <174653761499.406.4047609327811388776.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Precedence: bulk Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable The following commit has been merged into the irq/cleanups branch of tip: Commit-ID: 22909d92a0298a22a6cbe39644a03af6d62983e2 Gitweb: https://git.kernel.org/tip/22909d92a0298a22a6cbe39644a03af6d= 62983e2 Author: Jiri Slaby (SUSE) AuthorDate: Wed, 19 Mar 2025 10:29:47 +01:00 Committer: Thomas Gleixner CommitterDate: Tue, 06 May 2025 14:59:09 +02:00 Documentation: irq/concepts: Minor improvements Just note in the docs: 1) A PCI device as an example for shared interrupts 2) A sparse tree can be used for interrupts too 3) i8259s which have 8 pins [ tglx: Fix up subject prefix ] Signed-off-by: Jiri Slaby (SUSE) Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/all/20250319092951.37667-55-jirislaby@kernel.= org --- Documentation/core-api/irq/concepts.rst | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/Documentation/core-api/irq/concepts.rst b/Documentation/core-a= pi/irq/concepts.rst index f166006..7c4564f 100644 --- a/Documentation/core-api/irq/concepts.rst +++ b/Documentation/core-api/irq/concepts.rst @@ -4,18 +4,20 @@ What is an IRQ? =20 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. +the same pin thus sharing an IRQ. Such as on legacy PCI bus: All devices +typically share 4 lanes/pins. Note that each device can request an +interrupt on each of the lanes. =20 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. +array or sparse_irqs tree. But except for what linux/interrupt.h +implements, the details are architecture specific. =20 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 controllers in the system. In the case of ISA, -what is enumerated are the 16 input pins on the two i8259 interrupt -controllers. +what is enumerated are the 8 input pins on each of the two i8259 +interrupt controllers. =20 Architectures can assign additional meaning to the IRQ numbers, and are encouraged to in the case where there is any manual configuration