vystem/docs/shelter/devs/acpi.md

ACPI Parsing

Shelter only support the ACPI v2 and newer ACPI specifications. That mean the XSDT pointer must exists.

Root structures parsing

The root structures parsing is defined in shelter/lib/include/devs/acpi.h and implemented in shelter/lib/src/devs/acpi.c.

The sh_acpi_parse_rsdp() function takes the RSDP and completes a sh_apci_ACPI_POINTERS_ROOT structure that look like this:

typedef struct {
  sh_uint64 rsdt;
  sh_uint64 xsdt;
} sh_apci_ACPI_POINTERS_ROOT;

Then, the sh_acpi_parse_xsdt() function takes the XSDT pointer and parses the XSDT header. It ensures that the structure isn't corrupted, and map all the entries. At the end, it completes this structure:

typedef struct {
  sh_uint64 *entries;
  sh_uint64 entry_count;
} sh_acpi_ACPI_XSDT_BODY;

Finally, the sh_acpi_parse_tables() takes the sh_acpi_ACPI_XSDT_BODY structure and parses all the entries. It ensures that at least the first pages of each table is mapped. All the tables pointers are sorted in a structure that look like this:

typedef struct {
  sh_uint64 madt_physical_address;
} sh_acpi_ACPI_TABLES;

Tables parsing

The parsing of ACPI tables is delegated to several functions, one for each tables. Here are the tables that are currently supported:

• MADT

All parsing functions are defined in the files inside shelter/lib/include/devs/acpi_tables and in the files inside shelter/lib/src/devs/acpi_tables.

MADT parsing

The MADT is parsed using the sh_acpi_madt_parse(sh_uint64 madt_ptr), defined in shelter/lib/include/devs/acpi_tables/madt.h and implemented in shelter/lib/src/devs/acpi_tables/madt.c.

This function logs all the entries and register all LAPIC devices, IOAPIC devices and ISOs.