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| -rw-r--r-- | Documentation/core-api/irq/irq-domain.rst | 22 |
1 files changed, 11 insertions, 11 deletions
diff --git a/Documentation/core-api/irq/irq-domain.rst b/Documentation/core-api/irq/irq-domain.rst index c365c3ed4eba..cb25649d0bb7 100644 --- a/Documentation/core-api/irq/irq-domain.rst +++ b/Documentation/core-api/irq/irq-domain.rst @@ -1,19 +1,19 @@ =============================================== -The irq_domain interrupt number mapping library +The irq_domain Interrupt Number Mapping Library =============================================== The current design of the Linux kernel uses a single large number space where each separate IRQ source is assigned a different number. This is simple when there is only one interrupt controller, but in -systems with multiple interrupt controllers the kernel must ensure +systems with multiple interrupt controllers, the kernel must ensure that each one gets assigned non-overlapping allocations of Linux IRQ numbers. The number of interrupt controllers registered as unique irqchips -show a rising tendency: for example subdrivers of different kinds +shows a rising tendency. For example, subdrivers of different kinds such as GPIO controllers avoid reimplementing identical callback mechanisms as the IRQ core system by modelling their interrupt -handlers as irqchips, i.e. in effect cascading interrupt controllers. +handlers as irqchips. I.e. in effect cascading interrupt controllers. Here the interrupt number loose all kind of correspondence to hardware interrupt numbers: whereas in the past, IRQ numbers could @@ -21,15 +21,15 @@ be chosen so they matched the hardware IRQ line into the root interrupt controller (i.e. the component actually fireing the interrupt line to the CPU) nowadays this number is just a number. -For this reason we need a mechanism to separate controller-local -interrupt numbers, called hardware irq's, from Linux IRQ numbers. +For this reason, we need a mechanism to separate controller-local +interrupt numbers, called hardware IRQs, from Linux IRQ numbers. The irq_alloc_desc*() and irq_free_desc*() APIs provide allocation of irq numbers, but they don't provide any support for reverse mapping of the controller-local IRQ (hwirq) number into the Linux IRQ number space. -The irq_domain library adds mapping between hwirq and IRQ numbers on +The irq_domain library adds a mapping between hwirq and IRQ numbers on top of the irq_alloc_desc*() API. An irq_domain to manage mapping is preferred over interrupt controller drivers open coding their own reverse mapping scheme. @@ -38,7 +38,7 @@ irq_domain also implements translation from an abstract irq_fwspec structure to hwirq numbers (Device Tree and ACPI GSI so far), and can be easily extended to support other IRQ topology data sources. -irq_domain usage +irq_domain Usage ================ An interrupt controller driver creates and registers an irq_domain by @@ -76,7 +76,7 @@ If the driver has the Linux IRQ number or the irq_data pointer, and needs to know the associated hwirq number (such as in the irq_chip callbacks) then it can be directly obtained from irq_data->hwirq. -Types of irq_domain mappings +Types of irq_domain Mappings ============================ There are several mechanisms available for reverse mapping from hwirq @@ -101,7 +101,7 @@ map are fixed time lookup for IRQ numbers, and irq_descs are only allocated for in-use IRQs. The disadvantage is that the table must be as large as the largest possible hwirq number. -The majority of drivers should use the linear map. +The majority of drivers should use the Linear map. Tree ---- @@ -189,7 +189,7 @@ that the driver using the simple domain call irq_create_mapping() before any irq_find_mapping() since the latter will actually work for the static IRQ assignment case. -Hierarchy IRQ domain +Hierarchy IRQ Domain -------------------- On some architectures, there may be multiple interrupt controllers |