rajamesandClaude Opus 5.5
c95191736e
Each board has one serial line that is its console, the lowest common denominator beside the screen and keyboard. Its address was QEMU's, fixed: on a Raspberry Pi 5 the aarch64 one is ordinary RAM, written to with every character printed; on a Milk-V Mars the riscv64 one is the board's UART with registers four bytes apart, and the UEFI loader would have waited for ever on its first character; on a PC with no COM1 the prompt read 0xFF for ever. console_attach_serial(), called before anything prints: COM1 if a UART answers there; elsewhere the UART that /chosen/stdout-path names (fdt_uart.c: alias, path, the address carried up through each bus's ranges, reg-shift and reg-io-width); with no devicetree, QEMU's. A devicetree that names no usable console gives no line, not a guess. A line that does not come ready is given up, not waited on. The riscv64 loader's early serial does the same. tools/fdt_uart_test.c, run by hand, 19 checks plain and under the sanitizers: devicetrees shaped like the Mars's, the Pi 5's and QEMU's, what must find nothing, and a block cut short at every length; and the Pi 5's real devicetree gives a PL011 at 0x107d001000. Acceptance, one QEMU at a time: v3 on amd64 (logs/20261013-204436), aarch64 (-204803) and riscv64 (-205001) to the zuse prompt, no unknown word, hash 0x08873e0f44b7cb2a on all three as before. -204600 is an aarch64 run during which the disk images were restored under it by a script that had been refused a second QEMU; it passed and is kept, and was run again. v4 on the three ISAs (-211149, -211444, -211857): POST 538 of 538, dict_hash 0xe5a57f3eb72ff94a, the typed session unchanged. The Mars image through OpenSBI and U-Boot in QEMU took its line and its interrupt controller from the devicetree and passed POST. Found on the way and not mended (boards/BRINGUP.md 1.6): built with EMERGENCY_CONSOLE_ENABLED=1 the prompt floods with empty lines. -210442 shows it; the commit before this does the same. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
204 lines
9.0 KiB
C
204 lines
9.0 KiB
C
/*
|
||
StarForth — Steady-State Virtual Machine Runtime
|
||
Copyright (c) 2023–2025 Robert A. James. All rights reserved.
|
||
Licensed under the StarForth License, Version 1.0.
|
||
*/
|
||
|
||
/**
|
||
* fdt.h - Minimal flattened-devicetree reader
|
||
*
|
||
* Just enough of the Devicetree Specification v0.4 §5 to pull values out of
|
||
* the blob the UEFI firmware publishes under EFI_DTB_TABLE_GUID, or that a
|
||
* native (non-UEFI) boot entry passes directly. Read-only, no allocation, no
|
||
* tree construction — it walks the structure block each call, which is fine
|
||
* for the handful of boot-time lookups the kernel needs.
|
||
*
|
||
* Deliberately not a general devicetree library. Added for punch-list item
|
||
* 0.3 (riscv64 timebase-frequency); extended (FABRIC-3.md §IV.3/§V.3,
|
||
* 2026-09-04) with node-scoped lookup, for exactly the case this header
|
||
* originally flagged as a future need (item 0.6's aarch64 GIC) plus its
|
||
* real, concrete consumers as of this pass: the Raspberry Pi 5's UART/
|
||
* mailbox register addresses (native boot, no ACPI) and the Milk-V Mars's
|
||
* real PLIC base address (currently hardcoded to QEMU-virt's own value,
|
||
* `arch/riscv64/plic.c`'s own doc comment already warned this isn't
|
||
* assumed stable across configurations).
|
||
*/
|
||
|
||
#ifndef STARKERNEL_FDT_H
|
||
#define STARKERNEL_FDT_H
|
||
|
||
#include <stdint.h>
|
||
|
||
/**
|
||
* @brief Test whether @p fdt points at a valid flattened devicetree.
|
||
*
|
||
* Checks the 0xd00dfeed magic and that the structure and strings blocks lie
|
||
* inside totalsize. Does not validate the token stream.
|
||
*
|
||
* @param fdt Candidate blob; NULL is safe and returns 0.
|
||
* @return 1 if the header is usable, 0 otherwise.
|
||
*/
|
||
int fdt_valid(const void* fdt);
|
||
|
||
/**
|
||
* @brief Find the first property with @p name anywhere in the tree.
|
||
*
|
||
* Scans the structure block in document order and returns the first match
|
||
* regardless of which node it belongs to. That is sufficient for properties
|
||
* which are uniform across a machine (timebase-frequency being the case this
|
||
* was written for) and is *not* sufficient for anything node-scoped.
|
||
*
|
||
* @param fdt Blob, already checked with @c fdt_valid().
|
||
* @param name Property name, NUL-terminated.
|
||
* @param len_out Receives the property length in bytes; may be NULL.
|
||
* @return Pointer to the property value inside @p fdt, or NULL if not found.
|
||
* The value is big-endian as stored in the blob.
|
||
*/
|
||
const void* fdt_find_prop(const void* fdt, const char* name, uint32_t* len_out);
|
||
|
||
/**
|
||
* @brief Read a single-cell (32-bit) property by name.
|
||
*
|
||
* Convenience over @c fdt_find_prop() that also handles the big-endian
|
||
* conversion. Fails if the property is absent or not exactly 4 bytes.
|
||
*
|
||
* @param fdt Blob, already checked with @c fdt_valid().
|
||
* @param name Property name, NUL-terminated.
|
||
* @param out Receives the host-order value on success; untouched on failure.
|
||
* @return 1 on success, 0 on failure.
|
||
*/
|
||
int fdt_prop_u32(const void* fdt, const char* name, uint32_t* out);
|
||
|
||
/**
|
||
* @brief Find the first node whose "compatible" property matches @p compatible.
|
||
*
|
||
* "compatible" is a NUL-separated list of strings (DT spec §2.3.1) — matches
|
||
* if @p compatible equals any one entry in the list, not just the whole
|
||
* property verbatim. Scans the whole tree in document order; the first
|
||
* matching node wins if more than one exists.
|
||
*
|
||
* @param fdt Blob, already checked with @c fdt_valid().
|
||
* @param compatible Compatible string to match, NUL-terminated.
|
||
* @return An opaque handle to the matched node, for use with
|
||
* @c fdt_find_prop_in_node() only (not a raw offset or a pointer
|
||
* to anything else meaningful) — or NULL if no node matches.
|
||
*/
|
||
const void* fdt_find_node_by_compatible(const void* fdt, const char* compatible);
|
||
|
||
/**
|
||
* @brief Find the first node whose "device_type" property equals @p type.
|
||
*
|
||
* Some standard nodes (`/memory` per DT spec §3.4) are identified by
|
||
* `device_type`, not `compatible` — unlike `compatible`, `device_type` is a
|
||
* single NUL-terminated string, not a list, so this matches the whole
|
||
* property value rather than scanning entries within it. Scans the whole
|
||
* tree in document order; the first matching node wins if more than one
|
||
* exists.
|
||
*
|
||
* @param fdt Blob, already checked with @c fdt_valid().
|
||
* @param type device_type value to match, NUL-terminated.
|
||
* @return An opaque handle to the matched node, for use with
|
||
* @c fdt_find_prop_in_node() only — or NULL if no node matches.
|
||
*/
|
||
const void* fdt_find_node_by_device_type(const void* fdt, const char* type);
|
||
|
||
/**
|
||
* @brief Find the first node whose own name matches @p name.
|
||
*
|
||
* Node names follow the DT spec §2.2.1 `name[@unit-address]` convention —
|
||
* matches if @p name equals the node's name up to (not including) an `@`
|
||
* suffix, or the whole name if there is none. For a singleton node with
|
||
* no unit address (`/reserved-memory` being the concrete case this was
|
||
* added for), this is an exact match. Scans the whole tree in document
|
||
* order; the first matching node wins if more than one exists.
|
||
*
|
||
* @param fdt Blob, already checked with @c fdt_valid().
|
||
* @param name Node name to match, NUL-terminated, no `@` suffix.
|
||
* @return An opaque handle to the matched node, for use with
|
||
* @c fdt_find_prop_in_node() / @c fdt_next_child_node() only —
|
||
* or NULL if no node matches.
|
||
*/
|
||
const void* fdt_find_node_by_name(const void* fdt, const char* name);
|
||
|
||
/**
|
||
* @brief Iterate the direct children of one node.
|
||
*
|
||
* Pass @p prev_child as NULL to get the first child; pass a previous
|
||
* result back in to get the next one. Stops (returns NULL) once there are
|
||
* no more children. Skips over each child's own descendants correctly
|
||
* (so a child with grandchildren doesn't confuse the scan), but does not
|
||
* itself descend into them — only direct children of @p parent are ever
|
||
* returned.
|
||
*
|
||
* @param fdt Blob, already checked with @c fdt_valid().
|
||
* @param parent Handle from one of the `fdt_find_node_by_*()`
|
||
* functions.
|
||
* @param prev_child NULL for the first child, or a handle previously
|
||
* returned by this function for @p parent to
|
||
* continue from.
|
||
* @return Handle to the next direct child, for use with
|
||
* @c fdt_find_prop_in_node() / @c fdt_next_child_node() only —
|
||
* or NULL once @p parent's children are exhausted.
|
||
*/
|
||
const void* fdt_next_child_node(const void* fdt, const void* parent,
|
||
const void* prev_child);
|
||
|
||
/**
|
||
* @brief Find a property by name, scoped to one node.
|
||
*
|
||
* Like @c fdt_find_prop(), but scans only @p node's own direct properties
|
||
* (as returned by @c fdt_find_node_by_compatible()) — stops at the first
|
||
* child node or the end of @p node's property list, never descends into
|
||
* children, never continues into a sibling. This is the difference that
|
||
* matters for a property name like "reg", which is not unique across the
|
||
* tree the way "timebase-frequency" (the whole reason @c fdt_find_prop()
|
||
* was originally sufficient) happens to be.
|
||
*
|
||
* @param fdt Blob, already checked with @c fdt_valid().
|
||
* @param node Handle from @c fdt_find_node_by_compatible(); NULL is
|
||
* safe and returns NULL (propagates a failed node lookup
|
||
* without a separate caller-side check).
|
||
* @param name Property name, NUL-terminated.
|
||
* @param len_out Receives the property length in bytes; may be NULL.
|
||
* @return Pointer to the property value inside @p fdt, or NULL if not
|
||
* found (or if @p node is NULL). The value is big-endian as
|
||
* stored in the blob.
|
||
*/
|
||
const void* fdt_find_prop_in_node(const void* fdt, const void* node,
|
||
const char* name, uint32_t* len_out);
|
||
|
||
/**
|
||
* @brief Is the structure block whole?
|
||
* @c fdt_valid() checks the header; this checks also that the structure
|
||
* block ends with its end token, as a blob that has not been cut short
|
||
* does. A reader that takes a property's absence to mean its default
|
||
* (a UART's "reg-shift") must not be handed half a tree.
|
||
* @return 1 if @p fdt is valid and its structure block ends with FDT_END.
|
||
*/
|
||
int fdt_complete(const void* fdt);
|
||
|
||
/**
|
||
* @brief The root node.
|
||
* @param fdt Blob; checked with @c fdt_valid().
|
||
* @return Handle to the root node, for @c fdt_find_child() and
|
||
* @c fdt_find_prop_in_node(), or NULL.
|
||
*/
|
||
const void* fdt_root_node(const void* fdt);
|
||
|
||
/**
|
||
* @brief Find a direct child of a node by its whole name.
|
||
* The name is matched exactly, unit address included ("serial@10000000"
|
||
* is not "serial"), and is given with its length so that one component of
|
||
* a path can be passed without copying it. Only @p parent's own children
|
||
* are looked at, never their descendants.
|
||
* @param fdt Blob; checked with @c fdt_valid().
|
||
* @param parent Node handle; NULL is safe and returns NULL.
|
||
* @param name The child's name; need not be NUL-terminated.
|
||
* @param name_len Its length in bytes.
|
||
* @return Handle to the child, or NULL if @p parent has none of that name.
|
||
*/
|
||
const void* fdt_find_child(const void* fdt, const void* parent,
|
||
const char* name, uint32_t name_len);
|
||
|
||
#endif /* STARKERNEL_FDT_H */
|