// SPDX-License-Identifier: GPL-2.0

//! Abstractions for the PCI bus.
//!
//! C header: [`include/linux/pci.h`](srctree/include/linux/pci.h)

use crate::{
    alloc::flags::*,
    bindings, device,
    device_id::RawDeviceId,
    devres::Devres,
    driver,
    error::{to_result, Result},
    io::Io,
    io::IoRaw,
    str::CStr,
    types::{ARef, ForeignOwnable, Opaque},
    ThisModule,
};
use core::{
    marker::PhantomData,
    ops::Deref,
    ptr::{addr_of_mut, NonNull},
};
use kernel::prelude::*;

/// An adapter for the registration of PCI drivers.
pub struct Adapter<T: Driver>(T);

// SAFETY: A call to `unregister` for a given instance of `RegType` is guaranteed to be valid if
// a preceding call to `register` has been successful.
unsafe impl<T: Driver + 'static> driver::RegistrationOps for Adapter<T> {
    type RegType = bindings::pci_driver;

    unsafe fn register(
        pdrv: &Opaque<Self::RegType>,
        name: &'static CStr,
        module: &'static ThisModule,
    ) -> Result {
        // SAFETY: It's safe to set the fields of `struct pci_driver` on initialization.
        unsafe {
            (*pdrv.get()).name = name.as_char_ptr();
            (*pdrv.get()).probe = Some(Self::probe_callback);
            (*pdrv.get()).remove = Some(Self::remove_callback);
            (*pdrv.get()).id_table = T::ID_TABLE.as_ptr();
        }

        // SAFETY: `pdrv` is guaranteed to be a valid `RegType`.
        to_result(unsafe {
            bindings::__pci_register_driver(pdrv.get(), module.0, name.as_char_ptr())
        })
    }

    unsafe fn unregister(pdrv: &Opaque<Self::RegType>) {
        // SAFETY: `pdrv` is guaranteed to be a valid `RegType`.
        unsafe { bindings::pci_unregister_driver(pdrv.get()) }
    }
}

impl<T: Driver + 'static> Adapter<T> {
    extern "C" fn probe_callback(
        pdev: *mut bindings::pci_dev,
        id: *const bindings::pci_device_id,
    ) -> kernel::ffi::c_int {
        // SAFETY: The PCI bus only ever calls the probe callback with a valid pointer to a
        // `struct pci_dev`.
        //
        // INVARIANT: `pdev` is valid for the duration of `probe_callback()`.
        let pdev = unsafe { &*pdev.cast::<Device<device::Core>>() };

        // SAFETY: `DeviceId` is a `#[repr(transparent)` wrapper of `struct pci_device_id` and
        // does not add additional invariants, so it's safe to transmute.
        let id = unsafe { &*id.cast::<DeviceId>() };
        let info = T::ID_TABLE.info(id.index());

        match T::probe(pdev, info) {
            Ok(data) => {
                // Let the `struct pci_dev` own a reference of the driver's private data.
                // SAFETY: By the type invariant `pdev.as_raw` returns a valid pointer to a
                // `struct pci_dev`.
                unsafe { bindings::pci_set_drvdata(pdev.as_raw(), data.into_foreign() as _) };
            }
            Err(err) => return Error::to_errno(err),
        }

        0
    }

    extern "C" fn remove_callback(pdev: *mut bindings::pci_dev) {
        // SAFETY: The PCI bus only ever calls the remove callback with a valid pointer to a
        // `struct pci_dev`.
        let ptr = unsafe { bindings::pci_get_drvdata(pdev) };

        // SAFETY: `remove_callback` is only ever called after a successful call to
        // `probe_callback`, hence it's guaranteed that `ptr` points to a valid and initialized
        // `KBox<T>` pointer created through `KBox::into_foreign`.
        let _ = unsafe { KBox::<T>::from_foreign(ptr) };
    }
}

/// Declares a kernel module that exposes a single PCI driver.
///
/// # Example
///
///```ignore
/// kernel::module_pci_driver! {
///     type: MyDriver,
///     name: "Module name",
///     authors: ["Author name"],
///     description: "Description",
///     license: "GPL v2",
/// }
///```
#[macro_export]
macro_rules! module_pci_driver {
($($f:tt)*) => {
    $crate::module_driver!(<T>, $crate::pci::Adapter<T>, { $($f)* });
};
}

/// Abstraction for bindings::pci_device_id.
#[repr(transparent)]
#[derive(Clone, Copy)]
pub struct DeviceId(bindings::pci_device_id);

impl DeviceId {
    const PCI_ANY_ID: u32 = !0;

    /// Equivalent to C's `PCI_DEVICE` macro.
    ///
    /// Create a new `pci::DeviceId` from a vendor and device ID number.
    pub const fn from_id(vendor: u32, device: u32) -> Self {
        Self(bindings::pci_device_id {
            vendor,
            device,
            subvendor: DeviceId::PCI_ANY_ID,
            subdevice: DeviceId::PCI_ANY_ID,
            class: 0,
            class_mask: 0,
            driver_data: 0,
            override_only: 0,
        })
    }

    /// Equivalent to C's `PCI_DEVICE_CLASS` macro.
    ///
    /// Create a new `pci::DeviceId` from a class number and mask.
    pub const fn from_class(class: u32, class_mask: u32) -> Self {
        Self(bindings::pci_device_id {
            vendor: DeviceId::PCI_ANY_ID,
            device: DeviceId::PCI_ANY_ID,
            subvendor: DeviceId::PCI_ANY_ID,
            subdevice: DeviceId::PCI_ANY_ID,
            class,
            class_mask,
            driver_data: 0,
            override_only: 0,
        })
    }
}

// SAFETY:
// * `DeviceId` is a `#[repr(transparent)` wrapper of `pci_device_id` and does not add
//   additional invariants, so it's safe to transmute to `RawType`.
// * `DRIVER_DATA_OFFSET` is the offset to the `driver_data` field.
unsafe impl RawDeviceId for DeviceId {
    type RawType = bindings::pci_device_id;

    const DRIVER_DATA_OFFSET: usize = core::mem::offset_of!(bindings::pci_device_id, driver_data);

    fn index(&self) -> usize {
        self.0.driver_data as _
    }
}

/// IdTable type for PCI
pub type IdTable<T> = &'static dyn kernel::device_id::IdTable<DeviceId, T>;

/// Create a PCI `IdTable` with its alias for modpost.
#[macro_export]
macro_rules! pci_device_table {
    ($table_name:ident, $module_table_name:ident, $id_info_type: ty, $table_data: expr) => {
        const $table_name: $crate::device_id::IdArray<
            $crate::pci::DeviceId,
            $id_info_type,
            { $table_data.len() },
        > = $crate::device_id::IdArray::new($table_data);

        $crate::module_device_table!("pci", $module_table_name, $table_name);
    };
}

/// The PCI driver trait.
///
/// # Example
///
///```
/// # use kernel::{bindings, device::Core, pci};
///
/// struct MyDriver;
///
/// kernel::pci_device_table!(
///     PCI_TABLE,
///     MODULE_PCI_TABLE,
///     <MyDriver as pci::Driver>::IdInfo,
///     [
///         (pci::DeviceId::from_id(bindings::PCI_VENDOR_ID_REDHAT, bindings::PCI_ANY_ID as _), ())
///     ]
/// );
///
/// impl pci::Driver for MyDriver {
///     type IdInfo = ();
///     const ID_TABLE: pci::IdTable<Self::IdInfo> = &PCI_TABLE;
///
///     fn probe(
///         _pdev: &pci::Device<Core>,
///         _id_info: &Self::IdInfo,
///     ) -> Result<Pin<KBox<Self>>> {
///         Err(ENODEV)
///     }
/// }
///```
/// Drivers must implement this trait in order to get a PCI driver registered. Please refer to the
/// `Adapter` documentation for an example.
pub trait Driver: Send {
    /// The type holding information about each device id supported by the driver.
    ///
    /// TODO: Use associated_type_defaults once stabilized:
    ///
    /// type IdInfo: 'static = ();
    type IdInfo: 'static;

    /// The table of device ids supported by the driver.
    const ID_TABLE: IdTable<Self::IdInfo>;

    /// PCI driver probe.
    ///
    /// Called when a new platform device is added or discovered.
    /// Implementers should attempt to initialize the device here.
    fn probe(dev: &Device<device::Core>, id_info: &Self::IdInfo) -> Result<Pin<KBox<Self>>>;
}

/// The PCI device representation.
///
/// This structure represents the Rust abstraction for a C `struct pci_dev`. The implementation
/// abstracts the usage of an already existing C `struct pci_dev` within Rust code that we get
/// passed from the C side.
///
/// # Invariants
///
/// A [`Device`] instance represents a valid `struct device` created by the C portion of the kernel.
#[repr(transparent)]
pub struct Device<Ctx: device::DeviceContext = device::Normal>(
    Opaque<bindings::pci_dev>,
    PhantomData<Ctx>,
);

/// A PCI BAR to perform I/O-Operations on.
///
/// # Invariants
///
/// `Bar` always holds an `IoRaw` inststance that holds a valid pointer to the start of the I/O
/// memory mapped PCI bar and its size.
pub struct Bar<const SIZE: usize = 0> {
    pdev: ARef<Device>,
    io: IoRaw<SIZE>,
    num: i32,
}

impl<const SIZE: usize> Bar<SIZE> {
    fn new(pdev: &Device, num: u32, name: &CStr) -> Result<Self> {
        let len = pdev.resource_len(num)?;
        if len == 0 {
            return Err(ENOMEM);
        }

        // Convert to `i32`, since that's what all the C bindings use.
        let num = i32::try_from(num)?;

        // SAFETY:
        // `pdev` is valid by the invariants of `Device`.
        // `num` is checked for validity by a previous call to `Device::resource_len`.
        // `name` is always valid.
        let ret = unsafe { bindings::pci_request_region(pdev.as_raw(), num, name.as_char_ptr()) };
        if ret != 0 {
            return Err(EBUSY);
        }

        // SAFETY:
        // `pdev` is valid by the invariants of `Device`.
        // `num` is checked for validity by a previous call to `Device::resource_len`.
        // `name` is always valid.
        let ioptr: usize = unsafe { bindings::pci_iomap(pdev.as_raw(), num, 0) } as usize;
        if ioptr == 0 {
            // SAFETY:
            // `pdev` valid by the invariants of `Device`.
            // `num` is checked for validity by a previous call to `Device::resource_len`.
            unsafe { bindings::pci_release_region(pdev.as_raw(), num) };
            return Err(ENOMEM);
        }

        let io = match IoRaw::new(ioptr, len as usize) {
            Ok(io) => io,
            Err(err) => {
                // SAFETY:
                // `pdev` is valid by the invariants of `Device`.
                // `ioptr` is guaranteed to be the start of a valid I/O mapped memory region.
                // `num` is checked for validity by a previous call to `Device::resource_len`.
                unsafe { Self::do_release(pdev, ioptr, num) };
                return Err(err);
            }
        };

        Ok(Bar {
            pdev: pdev.into(),
            io,
            num,
        })
    }

    /// # Safety
    ///
    /// `ioptr` must be a valid pointer to the memory mapped PCI bar number `num`.
    unsafe fn do_release(pdev: &Device, ioptr: usize, num: i32) {
        // SAFETY:
        // `pdev` is valid by the invariants of `Device`.
        // `ioptr` is valid by the safety requirements.
        // `num` is valid by the safety requirements.
        unsafe {
            bindings::pci_iounmap(pdev.as_raw(), ioptr as _);
            bindings::pci_release_region(pdev.as_raw(), num);
        }
    }

    fn release(&self) {
        // SAFETY: The safety requirements are guaranteed by the type invariant of `self.pdev`.
        unsafe { Self::do_release(&self.pdev, self.io.addr(), self.num) };
    }
}

impl Bar {
    fn index_is_valid(index: u32) -> bool {
        // A `struct pci_dev` owns an array of resources with at most `PCI_NUM_RESOURCES` entries.
        index < bindings::PCI_NUM_RESOURCES
    }
}

impl<const SIZE: usize> Drop for Bar<SIZE> {
    fn drop(&mut self) {
        self.release();
    }
}

impl<const SIZE: usize> Deref for Bar<SIZE> {
    type Target = Io<SIZE>;

    fn deref(&self) -> &Self::Target {
        // SAFETY: By the type invariant of `Self`, the MMIO range in `self.io` is properly mapped.
        unsafe { Io::from_raw(&self.io) }
    }
}

impl Device {
    fn as_raw(&self) -> *mut bindings::pci_dev {
        self.0.get()
    }

    /// Returns the PCI vendor ID.
    pub fn vendor_id(&self) -> u16 {
        // SAFETY: `self.as_raw` is a valid pointer to a `struct pci_dev`.
        unsafe { (*self.as_raw()).vendor }
    }

    /// Returns the PCI device ID.
    pub fn device_id(&self) -> u16 {
        // SAFETY: `self.as_raw` is a valid pointer to a `struct pci_dev`.
        unsafe { (*self.as_raw()).device }
    }

    /// Returns the size of the given PCI bar resource.
    pub fn resource_len(&self, bar: u32) -> Result<bindings::resource_size_t> {
        if !Bar::index_is_valid(bar) {
            return Err(EINVAL);
        }

        // SAFETY:
        // - `bar` is a valid bar number, as guaranteed by the above call to `Bar::index_is_valid`,
        // - by its type invariant `self.as_raw` is always a valid pointer to a `struct pci_dev`.
        Ok(unsafe { bindings::pci_resource_len(self.as_raw(), bar.try_into()?) })
    }

    /// Mapps an entire PCI-BAR after performing a region-request on it. I/O operation bound checks
    /// can be performed on compile time for offsets (plus the requested type size) < SIZE.
    pub fn iomap_region_sized<const SIZE: usize>(
        &self,
        bar: u32,
        name: &CStr,
    ) -> Result<Devres<Bar<SIZE>>> {
        let bar = Bar::<SIZE>::new(self, bar, name)?;
        let devres = Devres::new(self.as_ref(), bar, GFP_KERNEL)?;

        Ok(devres)
    }

    /// Mapps an entire PCI-BAR after performing a region-request on it.
    pub fn iomap_region(&self, bar: u32, name: &CStr) -> Result<Devres<Bar>> {
        self.iomap_region_sized::<0>(bar, name)
    }
}

impl Device<device::Core> {
    /// Enable memory resources for this device.
    pub fn enable_device_mem(&self) -> Result {
        // SAFETY: `self.as_raw` is guaranteed to be a pointer to a valid `struct pci_dev`.
        to_result(unsafe { bindings::pci_enable_device_mem(self.as_raw()) })
    }

    /// Enable bus-mastering for this device.
    pub fn set_master(&self) {
        // SAFETY: `self.as_raw` is guaranteed to be a pointer to a valid `struct pci_dev`.
        unsafe { bindings::pci_set_master(self.as_raw()) };
    }
}

impl Deref for Device<device::Core> {
    type Target = Device;

    fn deref(&self) -> &Self::Target {
        let ptr: *const Self = self;

        // CAST: `Device<Ctx>` is a transparent wrapper of `Opaque<bindings::pci_dev>`.
        let ptr = ptr.cast::<Device>();

        // SAFETY: `ptr` was derived from `&self`.
        unsafe { &*ptr }
    }
}

impl From<&Device<device::Core>> for ARef<Device> {
    fn from(dev: &Device<device::Core>) -> Self {
        (&**dev).into()
    }
}

// SAFETY: Instances of `Device` are always reference-counted.
unsafe impl crate::types::AlwaysRefCounted for Device {
    fn inc_ref(&self) {
        // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
        unsafe { bindings::pci_dev_get(self.as_raw()) };
    }

    unsafe fn dec_ref(obj: NonNull<Self>) {
        // SAFETY: The safety requirements guarantee that the refcount is non-zero.
        unsafe { bindings::pci_dev_put(obj.cast().as_ptr()) }
    }
}

impl AsRef<device::Device> for Device {
    fn as_ref(&self) -> &device::Device {
        // SAFETY: By the type invariant of `Self`, `self.as_raw()` is a pointer to a valid
        // `struct pci_dev`.
        let dev = unsafe { addr_of_mut!((*self.as_raw()).dev) };

        // SAFETY: `dev` points to a valid `struct device`.
        unsafe { device::Device::as_ref(dev) }
    }
}

// SAFETY: A `Device` is always reference-counted and can be released from any thread.
unsafe impl Send for Device {}

// SAFETY: `Device` can be shared among threads because all methods of `Device`
// (i.e. `Device<Normal>) are thread safe.
unsafe impl Sync for Device {}