Vystem 0.2

docs/shelter/devs/acpi.md

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+# 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:
+``` C
+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:
+``` C
+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:
+``` C
+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.