RT-Thread RTOS
An open source embedded real-time operating system
OFW interrupts

Interrupts (<tt>irq.c</tt>)

Parse **interrupts**, **interrupt-parent**, and **interrupt-map** into logical IRQ numbers for PIC overview / **rt_pic_***.

Header: **drivers/ofw_irq.h**. Source: **components/drivers/ofw/irq.c**.

Two wiring styles

Style DTS Typical use
Direct **interrupts** + optional **interrupt-parent** SoC device on GIC
Mapped **interrupt-map** + **interrupt-map-mask** on bridge PCI, AMBA behind nexus

API

API Role
**rt_ofw_irq_cells(np)** **#interrupt-cells** of interrupt controller
**rt_ofw_find_irq_parent** Walk **interrupt-parent**; returns parent **np** and cell count
**rt_ofw_parse_irq_cells(np, index, &args)** Parse **interrupts** entry → **rt_ofw_cell_args**
**rt_ofw_parse_irq_map(np, &args)** Match **interrupt-map** row for this device
**rt_ofw_map_irq(&args)** Final logical IRQ number via PIC layer
**rt_ofw_get_irq_count** Number of interrupt specifiers
**rt_ofw_get_irq(np, index)** Convenience: parse + map in one call
**rt_ofw_get_irq_by_name** **interrupt-names** lookup

Recommended probe pattern

struct rt_ofw_cell_args irq_args;
int irq;
if (rt_ofw_get_prop(np, "interrupt-map", RT_NULL))
{
if (rt_ofw_parse_irq_map(np, &irq_args) != RT_EOK)
return -RT_ERROR;
}
else
{
if (rt_ofw_parse_irq_cells(np, 0, &irq_args) != RT_EOK)
return -RT_ERROR;
}
irq = rt_ofw_map_irq(&irq_args);
if (irq < 0)
return irq;
rt_pic_irq_enable(irq); /* subsystem-specific */

For multiple IRQs, loop **rt_ofw_get_irq(np, i)** or use **interrupt-names**.

<tt>interrupt-map</tt> (bridge)

Each map entry contains (per spec comment in **irq.c**):

  1. Child unit address (**#address-cells** of bridge)
  2. Child interrupt specifier (**#interrupt-cells** of bridge)
  3. **interrupt-parent** phandle
  4. Parent unit address
  5. Parent interrupt specifier

**interrupt-map-mask** masks bits before compare. PCI host bridges are the common case — see also PCI and device tree.

Pitfalls

Issue Mitigation
Missing **interrupt-parent** Must inherit from bus or use **interrupt-map**
Using **rt_ofw_get_irq** on PCI endpoint Often need **parse_irq_map** first
Cell count mismatch Verify parent **#interrupt-cells**
IRQ vs trigger type Specifier may include flags — pass full **irq_args** to PIC driver

See also