linux/Documentation/core-api/irq, branch master

Documentation: Add managed interrupts

2026-04-11T13:07:02Z

I stumbled upon "isolcpus=managed_irq" which is the last piece which can only be handled by isolcpus= and has no runtime knob. I knew roughly what managed interrupts should do but I lacked some details how it is used and what the managed_irq sub parameter means in practise. This documents what we have as of today and how it works. I added some examples how the parameter affects the configuration. Did I miss something? Given that the spreading as computed group_cpus_evenly() does not take the mask of isolated CPUs into account I'm not sure how relevant the managed_irq argument is. The virtio_scsi driver has no way to limit the interrupts and I don't see this for the nvme. Even if the number of queues can be reduced to two (as in the example) it is still spread evenly in the system instead and the isolated CPUs are not taken into account. To make this worse, you can even argue further whether or not the application on the isolated CPU wants to receive the interrupt directly or would prefer not to. Given all this, I am not sure if it makes sense to add 'io_queue' to the mix or if it could be incorporated into 'managed_irq'. One more point: Given that isolcpus= is marked deprecated as of commit b0d40d2b22fe4 ("sched/isolation: Document isolcpus= boot parameter flags, mark it deprecated") and the 'managed_irq' is evaluated at device's probe time it would require additional callbacks to re-evaluate the situation. Probably for 'io_queue', too. Does is make sense or should we simply drop the "deprecation" notice and allowing using it long term? Dynamic partitions work with cpusets, there this (managed_irq) limitation but is it really? And if static partition is the use case why bother. Signed-off-by: Sebastian Andrzej Siewior Reviewed-by: Ming Lei Reviewed-by: Aaron Tomlin Acked-by: Thomas Gleixner Signed-off-by: Jonathan Corbet Message-ID: <20260401110232.ET5RxZfl@linutronix.de>

Documentation: Fix core-api typos

2025-08-18T16:31:19Z

Fix typos. Signed-off-by: Bjorn Helgaas Reviewed-by: Randy Dunlap Signed-off-by: Jonathan Corbet Link: https://lore.kernel.org/r/20250813200526.290420-5-helgaas@kernel.org

irqdomain: Fix kernel-doc and add it to Documentation

2025-05-16T19:06:13Z

irqdomain.c's kernel-doc exists, but is not plugged into Documentation/ yet. Before plugging it in, fix it first: irq_domain_get_irq_data() and irq_domain_set_info() were documented twice. Identically, by both definitions for CONFIG_IRQ_DOMAIN_HIERARCHY and !CONFIG_IRQ_DOMAIN_HIERARCHY. Therefore, switch the second kernel-doc into an ordinary comment -- change "/**" to simple "/*". This avoids sphinx's: WARNING: Duplicate C declaration Next, in commit b7b377332b96 ("irqdomain: Fix the kernel-doc and plug it into Documentation"), irqdomain.h's (header) kernel-doc was added into core-api/genericirq.rst. But given the amount of irqdomain functions and structures, move all these to core-api/irq/irq-domain.rst now. Finally, add these newly fixed irqdomain.c's (source) docs there as well. Signed-off-by: Jiri Slaby (SUSE) Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/all/20250319092951.37667-58-jirislaby@kernel.org

Documentation: irqdomain: Update it

2025-05-16T19:06:13Z

The irqdomain documentaion became obsolete over time. Update and extend it a bit with respect to the current code and HW. Most notably the doubled documentation of irq_domain (from .rst and .h) was unified and let only in .rst. A reference link was added to .h. Furthermore: * Add some 'struct' keywords, so that the respective structs are hyperlinked * :c:member: use where appropriate to mark a member of a struct * Rephrase some wording to improve readability/understanding Signed-off-by: Jiri Slaby (SUSE) Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/all/20250319092951.37667-57-jirislaby@kernel.org

Documentation: irq-domain.rst: Simple improvements

2025-05-16T19:06:13Z

The improvements include: * Capitals in headlines. * Add commas: for easier reading, it is always desired to add commas at some places in text. Like before adverbs or after fronted sentences. * 3rd person -> add 's' to verbs. * End some sentences with period and start a new one. Avoid thus heavy sentences. [ tglx: Fix up subject prefix ] Signed-off-by: Jiri Slaby (SUSE) Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/all/20250319092951.37667-56-jirislaby@kernel.org

Documentation: irq/concepts: Minor improvements

2025-05-16T19:06:13Z

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: irq/concepts: Add commas and reflow

2025-05-16T19:06:13Z

For easier reading, it is always desired to add commas at some places in text. Like before adverbs or after fronted sentences. [ tglx: Fix up subject prefix ] Signed-off-by: Jiri Slaby (SUSE) Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/all/20250319092951.37667-54-jirislaby@kernel.org

irqdomain: Drop irq_linear_revmap()

2025-05-16T19:06:12Z

irq_linear_revmap() is deprecated and unused now. So remove it. Signed-off-by: Jiri Slaby (SUSE) Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/all/20250319092951.37667-50-jirislaby@kernel.org

irqdomain: Drop irq_domain_add_*() functions

2025-05-16T19:06:11Z

Most irq_domain_add_*() functions are unused now, so drop them. The remaining ones are moved to the deprecated section and will be removed during the merge window after the patches in various trees have been merged. Note: The Chinese docs are touched but unfinished. I cannot parse those. [ tglx: Remove the leftover in irq-domain.rst and handle merge logistics ] Signed-off-by: Jiri Slaby (SUSE) Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/all/20250319092951.37667-41-jirislaby@kernel.org

powerpc: Switch irq_domain_add_nomap() to use fwnode

2025-05-16T19:06:11Z

All irq_domain_add_*() functions are going away. PowerPC is the only user of irq_domain_add_nomap() and there is no irq_domain_create_nomap() complement. Therefore, to align with the rest of the kernel, rename irq_domain_add_nomap() to irq_domain_create_nomap() and accept a fwnode_handle instead of a device_node. [ tglx: Fix up subject prefix ] Signed-off-by: Jiri Slaby (SUSE) Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/all/20250319092951.37667-40-jirislaby@kernel.org