rework crate to allocationless (rust-osdev#131)

Rework crate to allocationless

An overall rework of structures to make the crate allocationless.
However, a new feature `allocator_api` has been added in addition
to these changes, which allows use of `PlatformInfo` and some other
allocating structures, by providing a `core::alloc::Allocator` in the
constructor of these types. This allows semantic interfacing with
existing allocation APIs, while also ensuring we aren't using the
`alloc` crate allocation behaviour by default, as it isn't very
extensible for use in bare-metal development contexts.

acpi/Cargo.toml

@@ -10,6 +10,9 @@ license = "MIT/Apache-2.0"
 edition = "2018"
 
 [dependencies]
-log = "0.4"
 bit_field = "0.10"
 rsdp = { version = "2", path = "../rsdp" }
+
+[features]
+default = ["allocator_api"]
+allocator_api = []

acpi/src/platform/address.rs → acpi/src/address.rs

@@ -75,7 +75,7 @@ pub struct GenericAddress {
 }
 
 impl GenericAddress {
-    pub(crate) fn from_raw(raw: RawGenericAddress) -> Result<GenericAddress, AcpiError> {
+    pub(crate) fn from_raw(raw: RawGenericAddress) -> crate::AcpiResult<GenericAddress> {
         let address_space = match raw.address_space {
             0x00 => AddressSpace::SystemMemory,
             0x01 => AddressSpace::SystemIo,

acpi/src/bgrt.rs

@@ -1,4 +1,7 @@
-use crate::{sdt::SdtHeader, AcpiTable};
+use crate::{
+    sdt::{SdtHeader, Signature},
+    AcpiTable,
+};
 use bit_field::BitField;
 
 /// The BGRT table contains information about a boot graphic that was displayed
@@ -15,7 +18,10 @@ pub struct Bgrt {
     image_offset_y: u32,
 }
 
-impl AcpiTable for Bgrt {
+/// ### Safety: Implementation properly represents a valid BGRT.
+unsafe impl AcpiTable for Bgrt {
+    const SIGNATURE: Signature = Signature::BGRT;
+
     fn header(&self) -> &SdtHeader {
         &self.header
     }

acpi/src/fadt.rs

@@ -1,12 +1,12 @@
 use crate::{
-    platform::address::{AccessSize, AddressSpace, GenericAddress, RawGenericAddress},
-    sdt::{ExtendedField, SdtHeader},
+    address::{AccessSize, AddressSpace, GenericAddress, RawGenericAddress},
+    sdt::{ExtendedField, SdtHeader, Signature},
     AcpiError,
     AcpiTable,
 };
 use bit_field::BitField;
 
-#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum PowerProfile {
     Unspecified,
     Desktop,
@@ -115,7 +115,10 @@ pub struct Fadt {
     hypervisor_vendor_id: ExtendedField<u64, 2>,
 }
 
-impl AcpiTable for Fadt {
+/// ### Safety: Implementation properly represents a valid FADT.
+unsafe impl AcpiTable for Fadt {
+    const SIGNATURE: Signature = Signature::FADT;
+
     fn header(&self) -> &SdtHeader {
         &self.header
     }

acpi/src/hpet.rs

@@ -1,4 +1,11 @@
-use crate::{platform::address::RawGenericAddress, sdt::SdtHeader, AcpiError, AcpiHandler, AcpiTable, AcpiTables};
+use crate::{
+    address::RawGenericAddress,
+    sdt::{SdtHeader, Signature},
+    AcpiError,
+    AcpiHandler,
+    AcpiTable,
+    AcpiTables,
+};
 use bit_field::BitField;
 
 #[derive(Debug)]
@@ -28,13 +35,9 @@ impl HpetInfo {
     where
         H: AcpiHandler,
     {
-        let hpet = unsafe {
-            tables
-                .get_sdt::<HpetTable>(crate::sdt::Signature::HPET)?
-                .ok_or(AcpiError::TableMissing(crate::sdt::Signature::HPET))?
-        };
+        let hpet = tables.find_table::<HpetTable>()?;
 
-        // Make sure the HPET's in system memory
+        // Make sure the HPET is in system memory
         assert_eq!(hpet.base_address.address_space, 0);
 
         Ok(HpetInfo {
@@ -86,7 +89,10 @@ pub struct HpetTable {
     page_protection_and_oem: u8,
 }
 
-impl AcpiTable for HpetTable {
+/// ### Safety: Implementation properly represents a valid HPET table.
+unsafe impl AcpiTable for HpetTable {
+    const SIGNATURE: Signature = Signature::HPET;
+
     fn header(&self) -> &SdtHeader {
         &self.header
     }