acpi-rs/aml/src/lib.rs

//! `aml` is a pure-Rust AML (ACPI Machine Language) parser, used for parsing the DSDT and
//! SSDT tables from ACPI. This crate can be used by kernels to gather information about the
//! hardware, and invoke control methods (this is not yet supported) to query and change the state
//! of devices in a hardware-independent way.
//!
//! ### Using the library
//! To use the library, you will mostly interact with the `AmlContext` type. You should create an
//! instance of this type using `AmlContext::new()`, and then pass it tables containing AML
//! (probably from the `acpi` crate), which you've mapped into the virtual address space. This will
//! parse the table, populating the namespace with objects encoded by the AML. After this, you may
//! unmap the memory the table was mapped into - all the information needed will be extracted and
//! allocated on the heap.
//!
//! You can then access specific objects by name like so: e.g.
//! ```ignore
//! let my_aml_value = aml_context.lookup(&AmlName::from_str("\\_SB.PCI0.S08._ADR").unwrap());
//! ```
// TODO: add example of invoking a method
//!
//! ### About the parser
//! The parser is written using a set of custom parser combinators - the code can be confusing on
//! first reading, but provides an extensible and type-safe way to write parsers. For an easy
//! introduction to parser combinators and the foundations used for this library, I suggest reading
//! [Bodil's fantastic blog post](https://bodil.lol/parser-combinators/).
//!
//! The actual combinators can be found in `parser.rs`. Various tricks are used to provide a nice
//! API and work around limitations in the type system, such as the concrete types like
//! `MapWithContext`, and the `make_parser_concrete` hack macro.
//!
//! The actual parsers are then grouped into categories based loosely on the AML grammar sections in
//! the ACPI spec. Most are written in terms of combinators, but some have to be written in a more
//! imperitive style, either because they're clearer, or because we haven't yet found good
//! combinator patterns to express the parse.

#![no_std]
#![feature(decl_macro, type_ascription, box_syntax)]

extern crate alloc;

#[cfg(test)]
extern crate std;

#[cfg(test)]
mod test_utils;

pub(crate) mod misc;
pub(crate) mod name_object;
pub(crate) mod namespace;
pub(crate) mod opcode;
pub(crate) mod parser;
pub mod pci_routing;
pub(crate) mod pkg_length;
pub mod resource;
pub(crate) mod term_object;
pub(crate) mod type1;
pub(crate) mod type2;
pub mod value;

pub use crate::{
    namespace::{AmlHandle, AmlName, Namespace},
    value::AmlValue,
};

use alloc::{boxed::Box, string::ToString};
use core::mem;
use log::error;
use misc::{ArgNum, LocalNum};
use name_object::Target;
use namespace::LevelType;
use parser::Parser;
use pkg_length::PkgLength;
use term_object::term_list;
use value::{AmlType, Args};

/// AML has a `RevisionOp` operator that returns the "AML interpreter revision". It's not clear
/// what this is actually used for, but this is ours.
pub const AML_INTERPRETER_REVISION: u64 = 0;

/// Describes how much debug information the parser should emit. Set the "maximum" expected verbosity in
/// the context's `debug_verbosity` - everything will be printed that is less or equal in 'verbosity'.
#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Debug)]
pub enum DebugVerbosity {
    /// Print no debug information
    None,
    /// Print heads and tails when entering and leaving scopes of major objects, but not more minor ones.
    Scopes,
    /// Print heads and tails when entering and leaving scopes of all objects.
    AllScopes,
    /// Print heads and tails of all objects, and extra debug information as it's parsed.
    All,
}

struct MethodContext {
    /*
     * AML local variables. These are used when we invoke a control method. A `None` value
     * represents a null AML object.
     */
    local_0: Option<AmlValue>,
    local_1: Option<AmlValue>,
    local_2: Option<AmlValue>,
    local_3: Option<AmlValue>,
    local_4: Option<AmlValue>,
    local_5: Option<AmlValue>,
    local_6: Option<AmlValue>,
    local_7: Option<AmlValue>,

    /// If we're currently invoking a control method, this stores the arguments that were passed to
    /// it. It's `None` if we aren't invoking a method.
    args: Args,
}

impl MethodContext {
    fn new(args: Args) -> MethodContext {
        MethodContext {
            local_0: None,
            local_1: None,
            local_2: None,
            local_3: None,
            local_4: None,
            local_5: None,
            local_6: None,
            local_7: None,
            args,
        }
    }
}

pub struct AmlContext {
    /// The `Handler` passed from the library user. This is stored as a boxed trait object simply to avoid having
    /// to add a lifetime and type parameter to `AmlContext`, as they would massively complicate the parser types.
    handler: Box<dyn Handler>,

    pub namespace: Namespace,
    method_context: Option<MethodContext>,

    /*
     * These track the state of the context while it's parsing an AML table.
     */
    current_scope: AmlName,
    scope_indent: usize,
    debug_verbosity: DebugVerbosity,
}

impl AmlContext {
    /// Creates a new `AmlContext` - the central type in managing the AML tables. Only one of these should be
    /// created, and it should be passed the DSDT and all SSDTs defined by the hardware.
    pub fn new(handler: Box<dyn Handler>, debug_verbosity: DebugVerbosity) -> AmlContext {
        let mut context = AmlContext {
            handler,
            namespace: Namespace::new(),
            method_context: None,

            current_scope: AmlName::root(),
            scope_indent: 0,
            debug_verbosity,
        };

        context.add_predefined_objects();
        context
    }

    pub fn parse_table(&mut self, stream: &[u8]) -> Result<(), AmlError> {
        if stream.len() == 0 {
            return Err(AmlError::UnexpectedEndOfStream);
        }

        let table_length = PkgLength::from_raw_length(stream, stream.len() as u32).unwrap();
        match term_object::term_list(table_length).parse(stream, self) {
            Ok(_) => Ok(()),
            Err((_, _, err)) => {
                error!("Failed to parse AML stream. Err = {:?}", err);
                Err(err)
            }
        }
    }

    // TODO: docs
    pub fn invoke_method(&mut self, path: &AmlName, args: Args) -> Result<AmlValue, AmlError> {
        match self.namespace.get_by_path(path)?.clone() {
            AmlValue::Method { flags, code } => {
                /*
                 * First, set up the state we expect to enter the method with, but clearing local
                 * variables to "null" and setting the arguments. Save the current method state and scope, so if we're
                 * already executing another control method, we resume into it correctly.
                 */
                let old_context = mem::replace(&mut self.method_context, Some(MethodContext::new(args)));
                let old_scope = mem::replace(&mut self.current_scope, path.clone());

                /*
                 * Create a namespace level to store local objects created by the invocation.
                 */
                self.namespace.add_level(path.clone(), LevelType::MethodLocals)?;

                let return_value = match term_list(PkgLength::from_raw_length(&code, code.len() as u32).unwrap())
                    .parse(&code, self)
                {
                    // If the method doesn't return a value, we implicitly return `0`
                    Ok(_) => Ok(AmlValue::Integer(0)),
                    Err((_, _, AmlError::Return(result))) => Ok(result),
                    Err((_, _, err)) => {
                        error!("Failed to execute control method: {:?}", err);
                        Err(err)
                    }
                };

                /*
                 * Locally-created objects should be destroyed on method exit (see §5.5.2.3 of the ACPI spec). We do
                 * this by simply removing the method's local object layer.
                 */
                // TODO: this should also remove objects created by the method outside the method's scope, if they
                // weren't statically created. This is harder.
                self.namespace.remove_level(path.clone())?;

                /*
                 * Restore the old state.
                 */
                self.method_context = old_context;
                self.current_scope = old_scope;

                return_value
            }

            /*
             * AML can encode methods that don't require any computation simply as the value that would otherwise be
             * returned (e.g. a `_STA` object simply being an `AmlValue::Integer`, instead of a method that just
             * returns an integer).
             */
            value => Ok(value),
        }
    }

    // TODO: docs
    pub fn initialize_objects(&mut self) -> Result<(), AmlError> {
        use name_object::NameSeg;
        use namespace::NamespaceLevel;
        use value::StatusObject;

        /*
         * If `\_SB._INI` exists, we unconditionally execute it at the beginning of device initialization.
         */
        match self.invoke_method(&AmlName::from_str("\\_SB._INI").unwrap(), Args::default()) {
            Ok(_) => (),
            Err(AmlError::ValueDoesNotExist(_)) => (),
            Err(err) => return Err(err),
        }

        /*
         * Next, we traverse the namespace, looking for devices.
         *
         * XXX: we clone the namespace here, which obviously drives up heap burden quite a bit (not as much as you
         * might first expect though - we're only duplicating the level data structure, not all the objects). The
         * issue here is that we need to access the namespace during traversal (e.g. to invoke a method), which the
         * borrow checker really doesn't like. A better solution could be a iterator-like traversal system that
         * keeps track of the namespace without keeping it borrowed. This works for now.
         */
        self.namespace.clone().traverse(|path, level: &NamespaceLevel| match level.typ {
            LevelType::Device => {
                let status = if level.values.contains_key(&NameSeg::from_str("_STA").unwrap()) {
                    self.invoke_method(&AmlName::from_str("_STA").unwrap().resolve(&path)?, Args::default())?
                        .as_status()?
                } else {
                    StatusObject::default()
                };

                /*
                 * If the device is present and has an `_INI` method, invoke it.
                 */
                if status.present && level.values.contains_key(&NameSeg::from_str("_INI").unwrap()) {
                    log::info!("Invoking _INI at level: {}", path);
                    self.invoke_method(&AmlName::from_str("_INI").unwrap().resolve(&path)?, Args::default())?;
                }

                /*
                 * We traverse the children of this device if it's present, or isn't present but is functional.
                 */
                Ok(status.present || status.functional)
            }

            LevelType::Scope => Ok(true),

            // TODO: can either of these contain devices?
            LevelType::Processor => Ok(false),
            LevelType::MethodLocals => Ok(false),
        })?;

        Ok(())
    }

    /// Get the value of an argument by its argument number. Can only be executed from inside a control method.
    pub(crate) fn current_arg(&self, arg: ArgNum) -> Result<&AmlValue, AmlError> {
        self.method_context.as_ref().ok_or(AmlError::NotExecutingControlMethod)?.args.arg(arg)
    }

    /// Get the current value of a local by its local number. Can only be executed from inside a control method.
    pub(crate) fn local(&self, local: LocalNum) -> Result<&AmlValue, AmlError> {
        if let None = self.method_context {
            return Err(AmlError::NotExecutingControlMethod);
        }

        match local {
            0 => self.method_context.as_ref().unwrap().local_0.as_ref().ok_or(AmlError::InvalidLocalAccess(local)),
            1 => self.method_context.as_ref().unwrap().local_1.as_ref().ok_or(AmlError::InvalidLocalAccess(local)),
            2 => self.method_context.as_ref().unwrap().local_2.as_ref().ok_or(AmlError::InvalidLocalAccess(local)),
            3 => self.method_context.as_ref().unwrap().local_3.as_ref().ok_or(AmlError::InvalidLocalAccess(local)),
            4 => self.method_context.as_ref().unwrap().local_4.as_ref().ok_or(AmlError::InvalidLocalAccess(local)),
            5 => self.method_context.as_ref().unwrap().local_5.as_ref().ok_or(AmlError::InvalidLocalAccess(local)),
            6 => self.method_context.as_ref().unwrap().local_6.as_ref().ok_or(AmlError::InvalidLocalAccess(local)),
            7 => self.method_context.as_ref().unwrap().local_7.as_ref().ok_or(AmlError::InvalidLocalAccess(local)),
            _ => Err(AmlError::InvalidLocalAccess(local)),
        }
    }

    /// Perform a store into a `Target`. This returns a value read out of the target, if neccessary, as values can
    /// be altered during a store in some circumstances. If the target is a `Name`, this also performs required
    /// implicit conversions. Stores to other targets are semantically equivalent to a `CopyObject`.
    pub(crate) fn store(&mut self, target: Target, value: AmlValue) -> Result<AmlValue, AmlError> {
        match target {
            Target::Name(ref path) => {
                let (_, handle) = self.namespace.search(path, &self.current_scope)?;
                let converted_object = match self.namespace.get(handle).unwrap().type_of() {
                    /*
                     * We special-case FieldUnits here because we don't have the needed information to actually do
                     * the write if we try and convert using `as_type`.
                     */
                    AmlType::FieldUnit => {
                        let mut field = self.namespace.get(handle).unwrap().clone();
                        field.write_field(value, self)?;
                        field.read_field(self)?
                    }
                    typ => value.as_type(typ, self)?,
                };

                *self.namespace.get_mut(handle)? = converted_object;
                Ok(self.namespace.get(handle)?.clone())
            }

            Target::Debug => {
                // TODO
                unimplemented!()
            }

            Target::Arg(arg_num) => {
                if let None = self.method_context {
                    return Err(AmlError::NotExecutingControlMethod);
                }

                match arg_num {
                    1 => self.method_context.as_mut().unwrap().args.arg_1 = Some(value.clone()),
                    2 => self.method_context.as_mut().unwrap().args.arg_2 = Some(value.clone()),
                    3 => self.method_context.as_mut().unwrap().args.arg_3 = Some(value.clone()),
                    4 => self.method_context.as_mut().unwrap().args.arg_4 = Some(value.clone()),
                    5 => self.method_context.as_mut().unwrap().args.arg_5 = Some(value.clone()),
                    6 => self.method_context.as_mut().unwrap().args.arg_6 = Some(value.clone()),
                    _ => return Err(AmlError::InvalidArgAccess(arg_num)),
                }
                Ok(value)
            }

            Target::Local(local_num) => {
                if let None = self.method_context {
                    return Err(AmlError::NotExecutingControlMethod);
                }

                match local_num {
                    0 => self.method_context.as_mut().unwrap().local_0 = Some(value.clone()),
                    1 => self.method_context.as_mut().unwrap().local_1 = Some(value.clone()),
                    2 => self.method_context.as_mut().unwrap().local_2 = Some(value.clone()),
                    3 => self.method_context.as_mut().unwrap().local_3 = Some(value.clone()),
                    4 => self.method_context.as_mut().unwrap().local_4 = Some(value.clone()),
                    5 => self.method_context.as_mut().unwrap().local_5 = Some(value.clone()),
                    6 => self.method_context.as_mut().unwrap().local_6 = Some(value.clone()),
                    7 => self.method_context.as_mut().unwrap().local_7 = Some(value.clone()),
                    _ => return Err(AmlError::InvalidLocalAccess(local_num)),
                }
                Ok(value)
            }

            Target::Null => Ok(value),
        }
    }

    /// Read from an operation-region, performing only standard-sized reads (supported powers-of-2 only. If a field
    /// is not one of these sizes, it may need to be masked, or multiple reads may need to be performed).
    pub(crate) fn read_region(&self, region_handle: AmlHandle, offset: u64, length: u64) -> Result<u64, AmlError> {
        use bit_field::BitField;
        use core::convert::TryInto;
        use value::RegionSpace;

        let (region_space, region_base, region_length, parent_device) = {
            if let AmlValue::OpRegion { region, offset, length, parent_device } =
                self.namespace.get(region_handle)?
            {
                (region, offset, length, parent_device)
            } else {
                return Err(AmlError::FieldRegionIsNotOpRegion);
            }
        };

        match region_space {
            RegionSpace::SystemMemory => {
                let address = (region_base + offset).try_into().map_err(|_| AmlError::FieldInvalidAddress)?;
                match length {
                    8 => Ok(self.handler.read_u8(address) as u64),
                    16 => Ok(self.handler.read_u16(address) as u64),
                    32 => Ok(self.handler.read_u32(address) as u64),
                    64 => Ok(self.handler.read_u64(address)),
                    _ => Err(AmlError::FieldInvalidAccessSize),
                }
            }

            RegionSpace::SystemIo => {
                let port = (region_base + offset).try_into().map_err(|_| AmlError::FieldInvalidAddress)?;
                match length {
                    8 => Ok(self.handler.read_io_u8(port) as u64),
                    16 => Ok(self.handler.read_io_u16(port) as u64),
                    32 => Ok(self.handler.read_io_u32(port) as u64),
                    _ => Err(AmlError::FieldInvalidAccessSize),
                }
            }

            RegionSpace::PciConfig => {
                /*
                 * First, we need to get some extra information out of objects in the parent object. Both
                 * `_SEG` and `_BBN` seem optional, with defaults that line up with legacy PCI implementations
                 * (e.g. systems with a single segment group and a single root, respectively).
                 */
                let parent_device = parent_device.as_ref().unwrap();
                let seg = match self.namespace.search(&AmlName::from_str("_SEG").unwrap(), parent_device) {
                    Ok((_, handle)) => self
                        .namespace
                        .get(handle)?
                        .as_integer(self)?
                        .try_into()
                        .map_err(|_| AmlError::FieldInvalidAddress)?,
                    Err(AmlError::ValueDoesNotExist(_)) => 0,
                    Err(err) => return Err(err),
                };
                let bbn = match self.namespace.search(&AmlName::from_str("_BBN").unwrap(), parent_device) {
                    Ok((_, handle)) => self
                        .namespace
                        .get(handle)?
                        .as_integer(self)?
                        .try_into()
                        .map_err(|_| AmlError::FieldInvalidAddress)?,
                    Err(AmlError::ValueDoesNotExist(_)) => 0,
                    Err(err) => return Err(err),
                };
                let adr = {
                    let (_, handle) = self.namespace.search(&AmlName::from_str("_ADR").unwrap(), parent_device)?;
                    self.namespace.get(handle)?.as_integer(self)?
                };

                let device = adr.get_bits(16..24) as u8;
                let function = adr.get_bits(0..8) as u8;
                let offset = (region_base + offset).try_into().map_err(|_| AmlError::FieldInvalidAddress)?;

                match length {
                    8 => Ok(self.handler.read_pci_u8(seg, bbn, device, function, offset) as u64),
                    16 => Ok(self.handler.read_pci_u16(seg, bbn, device, function, offset) as u64),
                    32 => Ok(self.handler.read_pci_u32(seg, bbn, device, function, offset) as u64),
                    _ => Err(AmlError::FieldInvalidAccessSize),
                }
            }

            // TODO
            _ => unimplemented!(),
        }
    }

    pub(crate) fn write_region(
        &mut self,
        region_handle: AmlHandle,
        offset: u64,
        length: u64,
        value: u64,
    ) -> Result<(), AmlError> {
        use bit_field::BitField;
        use core::convert::TryInto;
        use value::RegionSpace;

        let (region_space, region_base, region_length, parent_device) = {
            if let AmlValue::OpRegion { region, offset, length, parent_device } =
                self.namespace.get(region_handle)?
            {
                (region, offset, length, parent_device)
            } else {
                return Err(AmlError::FieldRegionIsNotOpRegion);
            }
        };

        match region_space {
            RegionSpace::SystemMemory => {
                let address = (region_base + offset).try_into().map_err(|_| AmlError::FieldInvalidAddress)?;
                match length {
                    8 => Ok(self.handler.write_u8(address, value as u8)),
                    16 => Ok(self.handler.write_u16(address, value as u16)),
                    32 => Ok(self.handler.write_u32(address, value as u32)),
                    64 => Ok(self.handler.write_u64(address, value)),
                    _ => Err(AmlError::FieldInvalidAccessSize),
                }
            }

            RegionSpace::SystemIo => {
                let port = (region_base + offset).try_into().map_err(|_| AmlError::FieldInvalidAddress)?;
                match length {
                    8 => Ok(self.handler.write_io_u8(port, value as u8)),
                    16 => Ok(self.handler.write_io_u16(port, value as u16)),
                    32 => Ok(self.handler.write_io_u32(port, value as u32)),
                    _ => Err(AmlError::FieldInvalidAccessSize),
                }
            }

            RegionSpace::PciConfig => {
                /*
                 * First, we need to get some extra information out of objects in the parent object. Both
                 * `_SEG` and `_BBN` seem optional, with defaults that line up with legacy PCI implementations
                 * (e.g. systems with a single segment group and a single root, respectively).
                 */
                let parent_device = parent_device.as_ref().unwrap();
                let seg = match self.namespace.search(&AmlName::from_str("_SEG").unwrap(), parent_device) {
                    Ok((_, handle)) => self
                        .namespace
                        .get(handle)?
                        .as_integer(self)?
                        .try_into()
                        .map_err(|_| AmlError::FieldInvalidAddress)?,
                    Err(AmlError::ValueDoesNotExist(_)) => 0,
                    Err(err) => return Err(err),
                };
                let bbn = match self.namespace.search(&AmlName::from_str("_BBN").unwrap(), parent_device) {
                    Ok((_, handle)) => self
                        .namespace
                        .get(handle)?
                        .as_integer(self)?
                        .try_into()
                        .map_err(|_| AmlError::FieldInvalidAddress)?,
                    Err(AmlError::ValueDoesNotExist(_)) => 0,
                    Err(err) => return Err(err),
                };
                let adr = {
                    let (_, handle) = self.namespace.search(&AmlName::from_str("_ADR").unwrap(), parent_device)?;
                    self.namespace.get(handle)?.as_integer(self)?
                };

                let device = adr.get_bits(16..24) as u8;
                let function = adr.get_bits(0..8) as u8;
                let offset = (region_base + offset).try_into().map_err(|_| AmlError::FieldInvalidAddress)?;

                match length {
                    8 => Ok(self.handler.write_pci_u8(seg, bbn, device, function, offset, value as u8)),
                    16 => Ok(self.handler.write_pci_u16(seg, bbn, device, function, offset, value as u16)),
                    32 => Ok(self.handler.write_pci_u32(seg, bbn, device, function, offset, value as u32)),
                    _ => Err(AmlError::FieldInvalidAccessSize),
                }
            }

            // TODO
            _ => unimplemented!(),
        }
    }

    fn add_predefined_objects(&mut self) {
        /*
         * In the dark ages of ACPI 1.0, before `\_OSI`, `\_OS` was used to communicate to the firmware which OS
         * was running. This was predictably not very good, and so was replaced in ACPI 3.0 with `_OSI`, which
         * allows support for individual capabilities to be queried. `_OS` should not be used by modern firmwares,
         * but to avoid problems we follow Linux in returning `"Microsoft Windows NT"`.
         *
         * See https://www.kernel.org/doc/html/latest/firmware-guide/acpi/osi.html for more information.
         */
        self.namespace
            .add_value(AmlName::from_str("\\_OS").unwrap(), AmlValue::String("Microsoft Windows NT".to_string()))
            .unwrap();

        /*
         * `\_OSI` was introduced by ACPI 3.0 to improve the situation created by `\_OS`. Unfortunately, exactly
         * the same problem was immediately repeated by introducing capabilities reflecting that an ACPI
         * implementation is exactly the same as a particular version of Windows' (e.g. firmwares will call
         * `\_OSI("Windows 2001")`).
         *
         * We basically follow suit with whatever Linux does, as this will hopefully minimise breakage:
         *    - We always claim `Windows *` compatability
         *    - We answer 'yes' to `_OSI("Darwin")
         *    - We answer 'no' to `_OSI("Linux")`, and report that the tables are doing the wrong thing
         */
        // TODO
        // self.namespace.add_value(AmlName::from_str("\\_OSI").unwrap(), todo!()).unwrap();

        /*
         * `\_REV` evaluates to the version of the ACPI specification supported by this interpreter. Linux did this
         * correctly until 2015, but firmwares misused this to detect Linux (as even modern versions of Windows
         * return `2`), and so they switched to just returning `2` (as we'll also do). `_REV` should be considered
         * useless and deprecated (this is mirrored in newer specs, which claim `2` means "ACPI 2 or greater").
         */
        self.namespace.add_value(AmlName::from_str("\\_REV").unwrap(), AmlValue::Integer(2)).unwrap();
    }
}

// TODO: docs
pub trait Handler {
    fn read_u8(&self, address: usize) -> u8;
    fn read_u16(&self, address: usize) -> u16;
    fn read_u32(&self, address: usize) -> u32;
    fn read_u64(&self, address: usize) -> u64;

    fn write_u8(&mut self, address: usize, value: u8);
    fn write_u16(&mut self, address: usize, value: u16);
    fn write_u32(&mut self, address: usize, value: u32);
    fn write_u64(&mut self, address: usize, value: u64);

    fn read_io_u8(&self, port: u16) -> u8;
    fn read_io_u16(&self, port: u16) -> u16;
    fn read_io_u32(&self, port: u16) -> u32;

    fn write_io_u8(&self, port: u16, value: u8);
    fn write_io_u16(&self, port: u16, value: u16);
    fn write_io_u32(&self, port: u16, value: u32);

    fn read_pci_u8(&self, segment: u16, bus: u8, device: u8, function: u8, offset: u16) -> u8;
    fn read_pci_u16(&self, segment: u16, bus: u8, device: u8, function: u8, offset: u16) -> u16;
    fn read_pci_u32(&self, segment: u16, bus: u8, device: u8, function: u8, offset: u16) -> u32;

    fn write_pci_u8(&self, segment: u16, bus: u8, device: u8, function: u8, offset: u16, value: u8);
    fn write_pci_u16(&self, segment: u16, bus: u8, device: u8, function: u8, offset: u16, value: u16);
    fn write_pci_u32(&self, segment: u16, bus: u8, device: u8, function: u8, offset: u16, value: u32);
}

#[derive(Clone, Debug, PartialEq, Eq)]
pub enum AmlError {
    /*
     * Errors produced parsing the AML stream.
     */
    UnexpectedEndOfStream,
    UnexpectedByte(u8),
    InvalidNameSeg,
    InvalidPkgLength,
    InvalidFieldFlags,
    IncompatibleValueConversion,
    UnterminatedStringConstant,
    InvalidStringConstant,
    InvalidRegionSpace(u8),
    /// Produced when a `DefPackage` contains a different number of elements to the package's length.
    MalformedPackage,
    /// Produced when a `DefBuffer` contains more bytes that its size.
    MalformedBuffer,
    /// Emitted by a parser when it's clear that the stream doesn't encode the object parsed by
    /// that parser (e.g. the wrong opcode starts the stream). This is handled specially by some
    /// parsers such as `or` and `choice!`.
    WrongParser,

    /*
     * Errors produced manipulating AML names.
     */
    EmptyNamesAreInvalid,
    /// Produced when trying to normalize a path that does not point to a valid level of the
    /// namespace. E.g. `\_SB.^^PCI0` goes above the root of the namespace. The contained value is the name that
    /// normalization was attempted upon.
    InvalidNormalizedName(AmlName),
    RootHasNoParent,

    /*
     * Errors produced working with the namespace.
     */
    /// Produced when a sub-level or value is added to a level that has not yet been added to the namespace. The
    /// `AmlName` is the name of the entire sub-level/value.
    LevelDoesNotExist(AmlName),
    ValueDoesNotExist(AmlName),
    /// Produced when two values with the same name are added to the namespace.
    NameCollision(AmlName),
    TriedToRemoveRootNamespace,

    /*
     * Errors produced executing control methods.
     */
    /// Produced when AML tries to do something only possible in a control method (e.g. read from an argument)
    /// when there's no control method executing.
    NotExecutingControlMethod,
    /// Produced when a method accesses an argument it does not have (e.g. a method that takes 2
    /// arguments accesses `Arg4`). The inner value is the number of the argument accessed.
    InvalidArgAccess(ArgNum),
    /// Produced when a method accesses a local that it has not stored into.
    InvalidLocalAccess(LocalNum),
    /// This is not a real error, but is used to propagate return values from within the deep
    /// parsing call-stack. It should only be emitted when parsing a `DefReturn`. We use the
    /// error system here because the way errors are propagated matches how we want to handle
    /// return values.
    Return(AmlValue),

    /*
     * Errors produced parsing the PCI routing tables (_PRT objects).
     */
    PrtInvalidAddress,
    PrtInvalidPin,
    PrtInvalidSource,
    PrtInvalidGsi,
    /// Produced when the PRT doesn't contain an entry for the requested address + pin
    PrtNoEntry,

    /*
     * Errors produced parsing Resource Descriptors.
     */
    ReservedResourceType,
    ResourceDescriptorTooShort,
    ResourceDescriptorTooLong,

    /*
     * Errors produced working with AML values.
     */
    InvalidStatusObject,
    InvalidShiftLeft,
    InvalidShiftRight,
    FieldRegionIsNotOpRegion,
    FieldInvalidAddress,
    FieldInvalidAccessSize,
    TypeCannotBeCompared(AmlType),
}