fdt.h File Reference

Header that interfaces with libfdt for Device Tree Blob (DTB) parsing. More...

#include "mem_layout/mem_layout.h"
#include "utils/kprintf.h"
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>

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Data Structures
struct	memory_region_t
	Represents a single physical memory span. More...
struct	memory_map_t
	Container for the system physical memory layout. More...
struct	interrupt_t
	Describes a single interrupt as parsed from an FDT "interrupts" specifier. More...

Macros
#define	MAX_MEM_REGIONS   16
	Maximum number of distinct memory regions the kernel will track.

Typedefs
typedef struct memory_region_t	memory_region_t
	Represents a single physical memory span.
typedef struct memory_map_t	memory_map_t
	Container for the system physical memory layout.
typedef enum irq_type_t	irq_type_t
	Interrupt category, as encoded in the first cell of an FDT "interrupts" property.
typedef enum irq_trigger_t	irq_trigger_t
	Signal shape used to trigger an interrupt.
typedef struct interrupt_t	interrupt_t
	Describes a single interrupt as parsed from an FDT "interrupts" specifier.

Enumerations
enum	irq_type_t { IRQ_TYPE_SPI = 0x0 , IRQ_TYPE_PPI = 0x1 }
	Interrupt category, as encoded in the first cell of an FDT "interrupts" property. More...
enum	irq_trigger_t { IRQ_TRIGGER_EDGE , IRQ_TRIGGER_LEVEL_HIGH }
	Signal shape used to trigger an interrupt. More...

Functions
static int32_t	interrupt_to_intid (const interrupt_t *const interrupt)
	Converts a parsed FDT interrupt specifier to its GIC INTID.
bool	check_fdt (const void *ptr)
	Check the validity of the Device Tree Blob (FDT).
int	get_mem (const void *fdt, memory_map_t *mmap)
	Scans the FDT for memory nodes and populates the provided map.
int	get_intc_node_offset (const void *fdt)
	Retrieves a pointer to the interrupt controller node in the FDT.
bool	fdt_is_error (int offset)
	Checks if the given FDT offset represents an error.
char *	get_compatible_string (const void *fdt, int node_offset)
	Retrieves the compatible string for a given node.
bool	get_reg_property (const void *fdt, int node_offset, memory_map_t *reg_map)
	Retrieves the register property for a given node.
int	get_intr_property (const void *fdt, int node_offset, interrupt_t *out_intr_array, size_t out_intr_array_len)
	Retrieves the interrupt property for a given node.
int	get_nodes_by_compatible (const void *fdt, const char *compatible, int *out_node_offsets, size_t out_node_offsets_len)
	Finds all nodes in the FDT matching a given "compatible" string.

Detailed Description

Header that interfaces with libfdt for Device Tree Blob (DTB) parsing.

Declares the kernel-facing FDT helper APIs used to validate and extract memory mapping information from the device tree.

Author

Abhin Parekadan Jose

Date

2026-05-16

Enumeration Type Documentation

irq_trigger_t

enum irq_trigger_t

Signal shape used to trigger an interrupt.

Enumerator
IRQ_TRIGGER_EDGE	Interrupt is asserted on a signal edge.
IRQ_TRIGGER_LEVEL_HIGH	Interrupt is asserted while the signal level is high.

irq_type_t

enum irq_type_t

Interrupt category, as encoded in the first cell of an FDT "interrupts" property.

Enumerator
IRQ_TYPE_SPI	Shared Peripheral Interrupt (routable to any core).
IRQ_TYPE_PPI	Private Peripheral Interrupt (local to a single core).

Function Documentation

check_fdt()

bool check_fdt

(

const void *

ptr

)

Check the validity of the Device Tree Blob (FDT).

Parameters

ptr	Pointer to the FDT in memory.

Returns

true if the FDT is valid, false otherwise.

fdt_is_error()

bool fdt_is_error

(

int

offset

)

Checks if the given FDT offset represents an error.

Parameters

offset

The FDT offset to check.

Returns

true if the offset is an error code, false otherwise.

get_compatible_string()

char * get_compatible_string	(	const void *	fdt,
		int	node_offset
	)

Retrieves the compatible string for a given node.

Parameters

fdt	Pointer to the FDT header in memory.
node_offset	Offset of the node for which to retrieve the compatible string.

Returns

Pointer to the compatible string, or NULL if not found.

get_intc_node_offset()

int get_intc_node_offset

(

const void *

fdt

)

Retrieves a pointer to the interrupt controller node in the FDT.

Parameters

fdt	Pointer to the FDT header in memory.

Returns

Offset of the interrupt controller node, or a negative libfdt error code if not found.

get_intr_property()

int get_intr_property	(	const void *	fdt,
		int	node_offset,
		interrupt_t *	out_intr_array,
		size_t	out_intr_array_len
	)

Retrieves the interrupt property for a given node.

Parameters

fdt	Pointer to the FDT header in memory.
node_offset	Offset of the node for which to retrieve the interrupt property.
out_intr_array	Array to be populated with the parsed interrupt specifiers.
out_intr_array_len	Number of elements available in out_intr_array.

Returns

The number of interrupt entries parsed (capped at out_intr_array_len), or a negative libfdt error code on failure.

get_mem()

int get_mem	(	const void *	fdt,
		memory_map_t *	mmap
	)

Scans the FDT for memory nodes and populates the provided map.

This function searches the FDT for nodes with device_type = "memory", respects the root node's #address-cells and #size-cells, and handles both 32-bit and 64-bit address formats.

Parameters

fdt	Pointer to the FDT header in memory.
mmap	Pointer to a memory_map_t structure to be populated.

Returns

0 on success, or a negative libfdt error code on failure.

get_nodes_by_compatible()

int get_nodes_by_compatible	(	const void *	fdt,
		const char *	compatible,
		int *	out_node_offsets,
		size_t	out_node_offsets_len
	)

Finds all nodes in the FDT matching a given "compatible" string.

Parameters

fdt	Pointer to the FDT header in memory.
compatible	Compatible string to search for.
out_node_offsets	Array to be populated with the offsets of matching nodes.
out_node_offsets_len	Number of elements available in out_node_offsets.

Returns

The number of matching nodes found (capped at out_node_offsets_len), or a negative libfdt error code on failure.

get_reg_property()

bool get_reg_property	(	const void *	fdt,
		int	node_offset,
		memory_map_t *	reg_map
	)

Retrieves the register property for a given node.

Parameters

fdt	Pointer to the FDT header in memory.
node_offset	Offset of the node for which to retrieve the register property.
reg_map	Pointer to a memory_map_t structure to be populated with register information.

Returns

true if the register property is found and successfully parsed, false otherwise.

interrupt_to_intid()

static int32_t interrupt_to_intid ( const interrupt_t *const  interrupt )

inlinestatic

Converts a parsed FDT interrupt specifier to its GIC INTID.

Per the ARM GIC devicetree binding, the "interrupts" cell's id is an offset within its category rather than the absolute INTID, so the base offset must be added back in: PPIs start at INTID 16, SPIs at INTID 32.

Parameters

interrupt

Interrupt specifier to convert.

Returns

The GIC INTID, or -1 if interrupt has an unrecognized type.