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@page page_device_pic_ofw PIC and device tree
# Device tree integration
How **`interrupts`** properties become virtual IRQs via **`irq_parse`** + **`irq_map`**.
Sources: **`pic.c`** (`ofw_pic_init`), **`ofw/irq.c`** (`rt_ofw_map_irq`).
---
## Boot: discovering controllers
**`rt_pic_init()`** → **`ofw_pic_init()`**:
```c
rt_ofw_foreach_node_by_prop(ic_np, "interrupt-controller")
rt_ofw_stub_probe_range(ic_np, &_pic_ofw_start, &_pic_ofw_end);
```
**`RT_PIC_OFW_DECLARE(name, ids, handler)`** expands to **`RT_OFW_STUB_EXPORT(..., pic, handler)`** — same mechanism as other OFW stubs, linker section **`.rt_ofw_data.stub.*`**.
Handler (e.g. **`gicv2_ofw_init`**) must:
1. Map MMIO
2. **`rt_pic_linear_irq`**
3. **`rt_pic_add_traps`** (root only)
4. **`rt_ofw_data(np) = &pic`**
---
## Device IRQ resolution
**`rt_dm_dev_get_irq(dev, index)`** → **`ofw_api_call(get_irq)`** → **`rt_ofw_get_irq`** → **`rt_ofw_map_irq`**.
### `rt_ofw_map_irq` (core logic)
```c
pic = rt_pic_dynamic_cast(rt_ofw_data(ic_np));
pic->ops->irq_parse(pic, irq_args, &pirq); /* RT_EOK == 0 */
irq = pic->ops->irq_map(pic, pirq.hwirq, pirq.mode);
```
| Step | Responsibility |
| --- | --- |
| **`rt_ofw_parse_irq_cells`** | Fill **`rt_ofw_cell_args`** from **`interrupts`** |
| **`irq_parse`** | Set **`out_pirq->hwirq`**, **`mode`** (GIC: type + number) |
| **`irq_map`** | **`rt_pic_config_irq`**, return **virtual IRQ** |
**`rt_pic_dynamic_cast`**: finds **`struct rt_pic`** embedded after **`rt_device`** or **`rt_object`** (name **`"PIC"`**).
---
## Example: GIC-style `#interrupt-cells` (3 cells)
From **`pic-gicv2.c`** / **`pic-gicv3.c`**:
| Cell 0 | Cell 1 | Cell 2 |
| --- | --- | --- |
| **0** = SPI, **1** = PPI, … | Interrupt number | Flags → **`RT_IRQ_MODE_*`** |
SPI DT number **0** → **hwirq 32** (`args[1] + 32`).
DTS example (Raspberry Pi 4, **`bcm2711-rpi-4-b.dts`**):
```dts
interrupts = <GIC_SPI 77 IRQ_TYPE_LEVEL_HIGH>;
```
---
## Secondary `interrupt-controller`
Child node must expose **`interrupt-controller`** + **`#interrupt-cells`** and set **`rt_ofw_data`** to its **`struct rt_pic`**.
Consumers use **`interrupt-parent = <&child_ic>`** or inherited parent.
**PCI `interrupt-map`**: resolves to parent GIC cells via @ref page_device_pci_ofw — still ends in **`rt_ofw_map_irq`**.
---
## Provider requirements for OFW
| `ops` | Required for DT devices |
| --- | --- |
| **`irq_parse`** | Yes |
| **`irq_map`** | Yes |
| **`irq_mask` / `irq_unmask`** | Strongly recommended |
Without **`irq_map`**, **`rt_ofw_map_irq`** logs error and fails.
---
## `RT_PIC_OFW_DECLARE` template
```c
static rt_err_t my_ic_ofw_init(struct rt_ofw_node *np, const struct rt_ofw_node_id *id)
{
/* map MMIO, fill my_pic.ops */
rt_pic_linear_irq(&my_pic, NUM_LINES);
rt_ofw_data(np) = &my_pic;
return RT_EOK;
}
static const struct rt_ofw_node_id my_ic_ids[] = {
{ .compatible = "vendor,my-ic" },
{ /* sentinel */ },
};
RT_PIC_OFW_DECLARE(my_ic, my_ic_ids, my_ic_ofw_init);
```
Non-root: no **`rt_pic_add_traps`**; use parent ISR or cascade.
---
## Pitfalls
| Issue | Mitigation |
| --- | --- |
| **`rt_ofw_data` NULL** | Provider not probed — **`rt_platform_ofw_request`** before cast |
| **`irq_parse` returns error** | **`rt_ofw_map_irq`** fails — check cell count |
| Wrong **`interrupt-parent`** | Walk **`rt_ofw_find_irq_parent`** in OFW IRQ code |
| Mix hwirq / virtual in driver | Only use **`rt_dm_dev_get_irq`** return value |
## See also
- @ref page_device_pic_irq_domain
- @ref page_device_ofw_irq
|
