1e00b0ab8SMauro Carvalho Chehab=============================================== 2e00b0ab8SMauro Carvalho ChehabThe irq_domain interrupt number mapping library 3e00b0ab8SMauro Carvalho Chehab=============================================== 4e00b0ab8SMauro Carvalho Chehab 5e00b0ab8SMauro Carvalho ChehabThe current design of the Linux kernel uses a single large number 6e00b0ab8SMauro Carvalho Chehabspace where each separate IRQ source is assigned a different number. 7e00b0ab8SMauro Carvalho ChehabThis is simple when there is only one interrupt controller, but in 8e00b0ab8SMauro Carvalho Chehabsystems with multiple interrupt controllers the kernel must ensure 9e00b0ab8SMauro Carvalho Chehabthat each one gets assigned non-overlapping allocations of Linux 10e00b0ab8SMauro Carvalho ChehabIRQ numbers. 11e00b0ab8SMauro Carvalho Chehab 12e00b0ab8SMauro Carvalho ChehabThe number of interrupt controllers registered as unique irqchips 13e00b0ab8SMauro Carvalho Chehabshow a rising tendency: for example subdrivers of different kinds 14e00b0ab8SMauro Carvalho Chehabsuch as GPIO controllers avoid reimplementing identical callback 15e00b0ab8SMauro Carvalho Chehabmechanisms as the IRQ core system by modelling their interrupt 16e00b0ab8SMauro Carvalho Chehabhandlers as irqchips, i.e. in effect cascading interrupt controllers. 17e00b0ab8SMauro Carvalho Chehab 18e00b0ab8SMauro Carvalho ChehabHere the interrupt number loose all kind of correspondence to 19e00b0ab8SMauro Carvalho Chehabhardware interrupt numbers: whereas in the past, IRQ numbers could 20e00b0ab8SMauro Carvalho Chehabbe chosen so they matched the hardware IRQ line into the root 21e00b0ab8SMauro Carvalho Chehabinterrupt controller (i.e. the component actually fireing the 22e00b0ab8SMauro Carvalho Chehabinterrupt line to the CPU) nowadays this number is just a number. 23e00b0ab8SMauro Carvalho Chehab 24e00b0ab8SMauro Carvalho ChehabFor this reason we need a mechanism to separate controller-local 25e00b0ab8SMauro Carvalho Chehabinterrupt numbers, called hardware irq's, from Linux IRQ numbers. 26e00b0ab8SMauro Carvalho Chehab 27e00b0ab8SMauro Carvalho ChehabThe irq_alloc_desc*() and irq_free_desc*() APIs provide allocation of 28e00b0ab8SMauro Carvalho Chehabirq numbers, but they don't provide any support for reverse mapping of 29e00b0ab8SMauro Carvalho Chehabthe controller-local IRQ (hwirq) number into the Linux IRQ number 30e00b0ab8SMauro Carvalho Chehabspace. 31e00b0ab8SMauro Carvalho Chehab 32e00b0ab8SMauro Carvalho ChehabThe irq_domain library adds mapping between hwirq and IRQ numbers on 33e00b0ab8SMauro Carvalho Chehabtop of the irq_alloc_desc*() API. An irq_domain to manage mapping is 34e00b0ab8SMauro Carvalho Chehabpreferred over interrupt controller drivers open coding their own 35e00b0ab8SMauro Carvalho Chehabreverse mapping scheme. 36e00b0ab8SMauro Carvalho Chehab 37e00b0ab8SMauro Carvalho Chehabirq_domain also implements translation from an abstract irq_fwspec 38e00b0ab8SMauro Carvalho Chehabstructure to hwirq numbers (Device Tree and ACPI GSI so far), and can 39e00b0ab8SMauro Carvalho Chehabbe easily extended to support other IRQ topology data sources. 40e00b0ab8SMauro Carvalho Chehab 41e00b0ab8SMauro Carvalho Chehabirq_domain usage 42e00b0ab8SMauro Carvalho Chehab================ 43e00b0ab8SMauro Carvalho Chehab 44e00b0ab8SMauro Carvalho ChehabAn interrupt controller driver creates and registers an irq_domain by 4567196feaSAndy Shevchenkocalling one of the irq_domain_add_*() or irq_domain_create_*() functions 4667196feaSAndy Shevchenko(each mapping method has a different allocator function, more on that later). 4767196feaSAndy ShevchenkoThe function will return a pointer to the irq_domain on success. The caller 4867196feaSAndy Shevchenkomust provide the allocator function with an irq_domain_ops structure. 49e00b0ab8SMauro Carvalho Chehab 50e00b0ab8SMauro Carvalho ChehabIn most cases, the irq_domain will begin empty without any mappings 51e00b0ab8SMauro Carvalho Chehabbetween hwirq and IRQ numbers. Mappings are added to the irq_domain 52e00b0ab8SMauro Carvalho Chehabby calling irq_create_mapping() which accepts the irq_domain and a 53e00b0ab8SMauro Carvalho Chehabhwirq number as arguments. If a mapping for the hwirq doesn't already 54e00b0ab8SMauro Carvalho Chehabexist then it will allocate a new Linux irq_desc, associate it with 55e00b0ab8SMauro Carvalho Chehabthe hwirq, and call the .map() callback so the driver can perform any 56e00b0ab8SMauro Carvalho Chehabrequired hardware setup. 57e00b0ab8SMauro Carvalho Chehab 58991007baSMarc ZyngierOnce a mapping has been established, it can be retrieved or used via a 59991007baSMarc Zyngiervariety of methods: 60991007baSMarc Zyngier 61991007baSMarc Zyngier- irq_resolve_mapping() returns a pointer to the irq_desc structure 62991007baSMarc Zyngier for a given domain and hwirq number, and NULL if there was no 63991007baSMarc Zyngier mapping. 64991007baSMarc Zyngier- irq_find_mapping() returns a Linux IRQ number for a given domain and 65991007baSMarc Zyngier hwirq number, and 0 if there was no mapping 66991007baSMarc Zyngier- irq_linear_revmap() is now identical to irq_find_mapping(), and is 67991007baSMarc Zyngier deprecated 68991007baSMarc Zyngier- generic_handle_domain_irq() handles an interrupt described by a 69991007baSMarc Zyngier domain and a hwirq number 70991007baSMarc Zyngier 71991007baSMarc ZyngierNote that irq domain lookups must happen in contexts that are 72991007baSMarc Zyngiercompatible with a RCU read-side critical section. 73e00b0ab8SMauro Carvalho Chehab 74e00b0ab8SMauro Carvalho ChehabThe irq_create_mapping() function must be called *at least once* 75e00b0ab8SMauro Carvalho Chehabbefore any call to irq_find_mapping(), lest the descriptor will not 76e00b0ab8SMauro Carvalho Chehabbe allocated. 77e00b0ab8SMauro Carvalho Chehab 78e00b0ab8SMauro Carvalho ChehabIf the driver has the Linux IRQ number or the irq_data pointer, and 79e00b0ab8SMauro Carvalho Chehabneeds to know the associated hwirq number (such as in the irq_chip 80e00b0ab8SMauro Carvalho Chehabcallbacks) then it can be directly obtained from irq_data->hwirq. 81e00b0ab8SMauro Carvalho Chehab 82e00b0ab8SMauro Carvalho ChehabTypes of irq_domain mappings 83e00b0ab8SMauro Carvalho Chehab============================ 84e00b0ab8SMauro Carvalho Chehab 85e00b0ab8SMauro Carvalho ChehabThere are several mechanisms available for reverse mapping from hwirq 86e00b0ab8SMauro Carvalho Chehabto Linux irq, and each mechanism uses a different allocation function. 87e00b0ab8SMauro Carvalho ChehabWhich reverse map type should be used depends on the use case. Each 88e00b0ab8SMauro Carvalho Chehabof the reverse map types are described below: 89e00b0ab8SMauro Carvalho Chehab 90e00b0ab8SMauro Carvalho ChehabLinear 91e00b0ab8SMauro Carvalho Chehab------ 92e00b0ab8SMauro Carvalho Chehab 93e00b0ab8SMauro Carvalho Chehab:: 94e00b0ab8SMauro Carvalho Chehab 95e00b0ab8SMauro Carvalho Chehab irq_domain_add_linear() 96e00b0ab8SMauro Carvalho Chehab irq_domain_create_linear() 97e00b0ab8SMauro Carvalho Chehab 98e00b0ab8SMauro Carvalho ChehabThe linear reverse map maintains a fixed size table indexed by the 99e00b0ab8SMauro Carvalho Chehabhwirq number. When a hwirq is mapped, an irq_desc is allocated for 100e00b0ab8SMauro Carvalho Chehabthe hwirq, and the IRQ number is stored in the table. 101e00b0ab8SMauro Carvalho Chehab 102e00b0ab8SMauro Carvalho ChehabThe Linear map is a good choice when the maximum number of hwirqs is 103e00b0ab8SMauro Carvalho Chehabfixed and a relatively small number (~ < 256). The advantages of this 104e00b0ab8SMauro Carvalho Chehabmap are fixed time lookup for IRQ numbers, and irq_descs are only 105e00b0ab8SMauro Carvalho Chehaballocated for in-use IRQs. The disadvantage is that the table must be 106e00b0ab8SMauro Carvalho Chehabas large as the largest possible hwirq number. 107e00b0ab8SMauro Carvalho Chehab 108e00b0ab8SMauro Carvalho Chehabirq_domain_add_linear() and irq_domain_create_linear() are functionally 109e00b0ab8SMauro Carvalho Chehabequivalent, except for the first argument is different - the former 110e00b0ab8SMauro Carvalho Chehabaccepts an Open Firmware specific 'struct device_node', while the latter 111e00b0ab8SMauro Carvalho Chehabaccepts a more general abstraction 'struct fwnode_handle'. 112e00b0ab8SMauro Carvalho Chehab 113e00b0ab8SMauro Carvalho ChehabThe majority of drivers should use the linear map. 114e00b0ab8SMauro Carvalho Chehab 115e00b0ab8SMauro Carvalho ChehabTree 116e00b0ab8SMauro Carvalho Chehab---- 117e00b0ab8SMauro Carvalho Chehab 118e00b0ab8SMauro Carvalho Chehab:: 119e00b0ab8SMauro Carvalho Chehab 120e00b0ab8SMauro Carvalho Chehab irq_domain_add_tree() 121e00b0ab8SMauro Carvalho Chehab irq_domain_create_tree() 122e00b0ab8SMauro Carvalho Chehab 123e00b0ab8SMauro Carvalho ChehabThe irq_domain maintains a radix tree map from hwirq numbers to Linux 124e00b0ab8SMauro Carvalho ChehabIRQs. When an hwirq is mapped, an irq_desc is allocated and the 125e00b0ab8SMauro Carvalho Chehabhwirq is used as the lookup key for the radix tree. 126e00b0ab8SMauro Carvalho Chehab 127e00b0ab8SMauro Carvalho ChehabThe tree map is a good choice if the hwirq number can be very large 128e00b0ab8SMauro Carvalho Chehabsince it doesn't need to allocate a table as large as the largest 129e00b0ab8SMauro Carvalho Chehabhwirq number. The disadvantage is that hwirq to IRQ number lookup is 130e00b0ab8SMauro Carvalho Chehabdependent on how many entries are in the table. 131e00b0ab8SMauro Carvalho Chehab 132e00b0ab8SMauro Carvalho Chehabirq_domain_add_tree() and irq_domain_create_tree() are functionally 133e00b0ab8SMauro Carvalho Chehabequivalent, except for the first argument is different - the former 134e00b0ab8SMauro Carvalho Chehabaccepts an Open Firmware specific 'struct device_node', while the latter 135e00b0ab8SMauro Carvalho Chehabaccepts a more general abstraction 'struct fwnode_handle'. 136e00b0ab8SMauro Carvalho Chehab 137e00b0ab8SMauro Carvalho ChehabVery few drivers should need this mapping. 138e00b0ab8SMauro Carvalho Chehab 139e00b0ab8SMauro Carvalho ChehabNo Map 140e00b0ab8SMauro Carvalho Chehab------ 141e00b0ab8SMauro Carvalho Chehab 142e00b0ab8SMauro Carvalho Chehab:: 143e00b0ab8SMauro Carvalho Chehab 144e00b0ab8SMauro Carvalho Chehab irq_domain_add_nomap() 145e00b0ab8SMauro Carvalho Chehab 146e00b0ab8SMauro Carvalho ChehabThe No Map mapping is to be used when the hwirq number is 147e00b0ab8SMauro Carvalho Chehabprogrammable in the hardware. In this case it is best to program the 148e00b0ab8SMauro Carvalho ChehabLinux IRQ number into the hardware itself so that no mapping is 149e00b0ab8SMauro Carvalho Chehabrequired. Calling irq_create_direct_mapping() will allocate a Linux 150e00b0ab8SMauro Carvalho ChehabIRQ number and call the .map() callback so that driver can program the 151e00b0ab8SMauro Carvalho ChehabLinux IRQ number into the hardware. 152e00b0ab8SMauro Carvalho Chehab 153991007baSMarc ZyngierMost drivers cannot use this mapping, and it is now gated on the 154991007baSMarc ZyngierCONFIG_IRQ_DOMAIN_NOMAP option. Please refrain from introducing new 155991007baSMarc Zyngierusers of this API. 156e00b0ab8SMauro Carvalho Chehab 157e00b0ab8SMauro Carvalho ChehabLegacy 158e00b0ab8SMauro Carvalho Chehab------ 159e00b0ab8SMauro Carvalho Chehab 160e00b0ab8SMauro Carvalho Chehab:: 161e00b0ab8SMauro Carvalho Chehab 162e00b0ab8SMauro Carvalho Chehab irq_domain_add_simple() 163e00b0ab8SMauro Carvalho Chehab irq_domain_add_legacy() 16467196feaSAndy Shevchenko irq_domain_create_simple() 165b6e95788SAndy Shevchenko irq_domain_create_legacy() 166e00b0ab8SMauro Carvalho Chehab 167e00b0ab8SMauro Carvalho ChehabThe Legacy mapping is a special case for drivers that already have a 168e00b0ab8SMauro Carvalho Chehabrange of irq_descs allocated for the hwirqs. It is used when the 169e00b0ab8SMauro Carvalho Chehabdriver cannot be immediately converted to use the linear mapping. For 170e00b0ab8SMauro Carvalho Chehabexample, many embedded system board support files use a set of #defines 171e00b0ab8SMauro Carvalho Chehabfor IRQ numbers that are passed to struct device registrations. In that 172e00b0ab8SMauro Carvalho Chehabcase the Linux IRQ numbers cannot be dynamically assigned and the legacy 173e00b0ab8SMauro Carvalho Chehabmapping should be used. 174e00b0ab8SMauro Carvalho Chehab 175*0ddc5e55SMarc ZyngierAs the name implies, the \*_legacy() functions are deprecated and only 176991007baSMarc Zyngierexist to ease the support of ancient platforms. No new users should be 177*0ddc5e55SMarc Zyngieradded. Same goes for the \*_simple() functions when their use results 178*0ddc5e55SMarc Zyngierin the legacy behaviour. 179991007baSMarc Zyngier 180e00b0ab8SMauro Carvalho ChehabThe legacy map assumes a contiguous range of IRQ numbers has already 181e00b0ab8SMauro Carvalho Chehabbeen allocated for the controller and that the IRQ number can be 182e00b0ab8SMauro Carvalho Chehabcalculated by adding a fixed offset to the hwirq number, and 183e00b0ab8SMauro Carvalho Chehabvisa-versa. The disadvantage is that it requires the interrupt 184e00b0ab8SMauro Carvalho Chehabcontroller to manage IRQ allocations and it requires an irq_desc to be 185e00b0ab8SMauro Carvalho Chehaballocated for every hwirq, even if it is unused. 186e00b0ab8SMauro Carvalho Chehab 187e00b0ab8SMauro Carvalho ChehabThe legacy map should only be used if fixed IRQ mappings must be 188e00b0ab8SMauro Carvalho Chehabsupported. For example, ISA controllers would use the legacy map for 189e00b0ab8SMauro Carvalho Chehabmapping Linux IRQs 0-15 so that existing ISA drivers get the correct IRQ 190e00b0ab8SMauro Carvalho Chehabnumbers. 191e00b0ab8SMauro Carvalho Chehab 19267196feaSAndy ShevchenkoMost users of legacy mappings should use irq_domain_add_simple() or 19367196feaSAndy Shevchenkoirq_domain_create_simple() which will use a legacy domain only if an IRQ range 19467196feaSAndy Shevchenkois supplied by the system and will otherwise use a linear domain mapping. 19567196feaSAndy ShevchenkoThe semantics of this call are such that if an IRQ range is specified then 196e00b0ab8SMauro Carvalho Chehabdescriptors will be allocated on-the-fly for it, and if no range is 19767196feaSAndy Shevchenkospecified it will fall through to irq_domain_add_linear() or 19867196feaSAndy Shevchenkoirq_domain_create_linear() which means *no* irq descriptors will be allocated. 199e00b0ab8SMauro Carvalho Chehab 200e00b0ab8SMauro Carvalho ChehabA typical use case for simple domains is where an irqchip provider 201e00b0ab8SMauro Carvalho Chehabis supporting both dynamic and static IRQ assignments. 202e00b0ab8SMauro Carvalho Chehab 203e00b0ab8SMauro Carvalho ChehabIn order to avoid ending up in a situation where a linear domain is 204e00b0ab8SMauro Carvalho Chehabused and no descriptor gets allocated it is very important to make sure 205e00b0ab8SMauro Carvalho Chehabthat the driver using the simple domain call irq_create_mapping() 206e00b0ab8SMauro Carvalho Chehabbefore any irq_find_mapping() since the latter will actually work 207e00b0ab8SMauro Carvalho Chehabfor the static IRQ assignment case. 208e00b0ab8SMauro Carvalho Chehab 20967196feaSAndy Shevchenkoirq_domain_add_simple() and irq_domain_create_simple() as well as 210b6e95788SAndy Shevchenkoirq_domain_add_legacy() and irq_domain_create_legacy() are functionally 211b6e95788SAndy Shevchenkoequivalent, except for the first argument is different - the former 212b6e95788SAndy Shevchenkoaccepts an Open Firmware specific 'struct device_node', while the latter 213b6e95788SAndy Shevchenkoaccepts a more general abstraction 'struct fwnode_handle'. 214b6e95788SAndy Shevchenko 215e00b0ab8SMauro Carvalho ChehabHierarchy IRQ domain 216e00b0ab8SMauro Carvalho Chehab-------------------- 217e00b0ab8SMauro Carvalho Chehab 218e00b0ab8SMauro Carvalho ChehabOn some architectures, there may be multiple interrupt controllers 219e00b0ab8SMauro Carvalho Chehabinvolved in delivering an interrupt from the device to the target CPU. 220e00b0ab8SMauro Carvalho ChehabLet's look at a typical interrupt delivering path on x86 platforms:: 221e00b0ab8SMauro Carvalho Chehab 222e00b0ab8SMauro Carvalho Chehab Device --> IOAPIC -> Interrupt remapping Controller -> Local APIC -> CPU 223e00b0ab8SMauro Carvalho Chehab 224e00b0ab8SMauro Carvalho ChehabThere are three interrupt controllers involved: 225e00b0ab8SMauro Carvalho Chehab 226e00b0ab8SMauro Carvalho Chehab1) IOAPIC controller 227e00b0ab8SMauro Carvalho Chehab2) Interrupt remapping controller 228e00b0ab8SMauro Carvalho Chehab3) Local APIC controller 229e00b0ab8SMauro Carvalho Chehab 230e00b0ab8SMauro Carvalho ChehabTo support such a hardware topology and make software architecture match 231e00b0ab8SMauro Carvalho Chehabhardware architecture, an irq_domain data structure is built for each 232e00b0ab8SMauro Carvalho Chehabinterrupt controller and those irq_domains are organized into hierarchy. 233e00b0ab8SMauro Carvalho ChehabWhen building irq_domain hierarchy, the irq_domain near to the device is 234e00b0ab8SMauro Carvalho Chehabchild and the irq_domain near to CPU is parent. So a hierarchy structure 235e00b0ab8SMauro Carvalho Chehabas below will be built for the example above:: 236e00b0ab8SMauro Carvalho Chehab 237e00b0ab8SMauro Carvalho Chehab CPU Vector irq_domain (root irq_domain to manage CPU vectors) 238e00b0ab8SMauro Carvalho Chehab ^ 239e00b0ab8SMauro Carvalho Chehab | 240e00b0ab8SMauro Carvalho Chehab Interrupt Remapping irq_domain (manage irq_remapping entries) 241e00b0ab8SMauro Carvalho Chehab ^ 242e00b0ab8SMauro Carvalho Chehab | 243e00b0ab8SMauro Carvalho Chehab IOAPIC irq_domain (manage IOAPIC delivery entries/pins) 244e00b0ab8SMauro Carvalho Chehab 245e00b0ab8SMauro Carvalho ChehabThere are four major interfaces to use hierarchy irq_domain: 246e00b0ab8SMauro Carvalho Chehab 247e00b0ab8SMauro Carvalho Chehab1) irq_domain_alloc_irqs(): allocate IRQ descriptors and interrupt 248e00b0ab8SMauro Carvalho Chehab controller related resources to deliver these interrupts. 249e00b0ab8SMauro Carvalho Chehab2) irq_domain_free_irqs(): free IRQ descriptors and interrupt controller 250e00b0ab8SMauro Carvalho Chehab related resources associated with these interrupts. 251e00b0ab8SMauro Carvalho Chehab3) irq_domain_activate_irq(): activate interrupt controller hardware to 252e00b0ab8SMauro Carvalho Chehab deliver the interrupt. 253e00b0ab8SMauro Carvalho Chehab4) irq_domain_deactivate_irq(): deactivate interrupt controller hardware 254e00b0ab8SMauro Carvalho Chehab to stop delivering the interrupt. 255e00b0ab8SMauro Carvalho Chehab 256e00b0ab8SMauro Carvalho ChehabFollowing changes are needed to support hierarchy irq_domain: 257e00b0ab8SMauro Carvalho Chehab 258e00b0ab8SMauro Carvalho Chehab1) a new field 'parent' is added to struct irq_domain; it's used to 259e00b0ab8SMauro Carvalho Chehab maintain irq_domain hierarchy information. 260e00b0ab8SMauro Carvalho Chehab2) a new field 'parent_data' is added to struct irq_data; it's used to 261e00b0ab8SMauro Carvalho Chehab build hierarchy irq_data to match hierarchy irq_domains. The irq_data 262e00b0ab8SMauro Carvalho Chehab is used to store irq_domain pointer and hardware irq number. 263e00b0ab8SMauro Carvalho Chehab3) new callbacks are added to struct irq_domain_ops to support hierarchy 264e00b0ab8SMauro Carvalho Chehab irq_domain operations. 265e00b0ab8SMauro Carvalho Chehab 266e00b0ab8SMauro Carvalho ChehabWith support of hierarchy irq_domain and hierarchy irq_data ready, an 267e00b0ab8SMauro Carvalho Chehabirq_domain structure is built for each interrupt controller, and an 268e00b0ab8SMauro Carvalho Chehabirq_data structure is allocated for each irq_domain associated with an 269e00b0ab8SMauro Carvalho ChehabIRQ. Now we could go one step further to support stacked(hierarchy) 270e00b0ab8SMauro Carvalho Chehabirq_chip. That is, an irq_chip is associated with each irq_data along 271e00b0ab8SMauro Carvalho Chehabthe hierarchy. A child irq_chip may implement a required action by 272e00b0ab8SMauro Carvalho Chehabitself or by cooperating with its parent irq_chip. 273e00b0ab8SMauro Carvalho Chehab 274e00b0ab8SMauro Carvalho ChehabWith stacked irq_chip, interrupt controller driver only needs to deal 275e00b0ab8SMauro Carvalho Chehabwith the hardware managed by itself and may ask for services from its 276e00b0ab8SMauro Carvalho Chehabparent irq_chip when needed. So we could achieve a much cleaner 277e00b0ab8SMauro Carvalho Chehabsoftware architecture. 278e00b0ab8SMauro Carvalho Chehab 279e00b0ab8SMauro Carvalho ChehabFor an interrupt controller driver to support hierarchy irq_domain, it 280e00b0ab8SMauro Carvalho Chehabneeds to: 281e00b0ab8SMauro Carvalho Chehab 282e00b0ab8SMauro Carvalho Chehab1) Implement irq_domain_ops.alloc and irq_domain_ops.free 283e00b0ab8SMauro Carvalho Chehab2) Optionally implement irq_domain_ops.activate and 284e00b0ab8SMauro Carvalho Chehab irq_domain_ops.deactivate. 285e00b0ab8SMauro Carvalho Chehab3) Optionally implement an irq_chip to manage the interrupt controller 286e00b0ab8SMauro Carvalho Chehab hardware. 287e00b0ab8SMauro Carvalho Chehab4) No need to implement irq_domain_ops.map and irq_domain_ops.unmap, 288e00b0ab8SMauro Carvalho Chehab they are unused with hierarchy irq_domain. 289e00b0ab8SMauro Carvalho Chehab 290e00b0ab8SMauro Carvalho ChehabHierarchy irq_domain is in no way x86 specific, and is heavily used to 291e00b0ab8SMauro Carvalho Chehabsupport other architectures, such as ARM, ARM64 etc. 292e00b0ab8SMauro Carvalho Chehab 293e00b0ab8SMauro Carvalho ChehabDebugging 294e00b0ab8SMauro Carvalho Chehab========= 295e00b0ab8SMauro Carvalho Chehab 296e00b0ab8SMauro Carvalho ChehabMost of the internals of the IRQ subsystem are exposed in debugfs by 297e00b0ab8SMauro Carvalho Chehabturning CONFIG_GENERIC_IRQ_DEBUGFS on. 298