rust: pci: add basic PCI device / driver abstractions

Implement the basic PCI abstractions required to write a basic PCI
driver. This includes the following data structures:

The `pci::Driver` trait represents the interface to the driver and
provides `pci::Driver::probe` and `pci::Driver::remove` for the driver
to implement.

The `pci::Device` abstraction represents a `struct pci_dev` and provides
abstractions for common functions, such as `pci::Device::set_master`.

In order to provide the PCI specific parts to a generic
`driver::Registration` the `driver::DriverOps` trait is implemented by
the `pci::Adapter`.

`pci::DeviceId` implements PCI device IDs based on the generic
`driver::RawDevceId` abstraction.

This patch is based on previous work from FUJITA Tomonori.

Co-developed-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Co-developed-by: Philipp Stanner <pstanner@redhat.com>
Signed-off-by: Philipp Stanner <pstanner@redhat.com>
Signed-off-by: Danilo Krummrich <dakr@redhat.com>

4 files changed, 346 insertions, 0 deletions

diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index b940a5777330..eecc2d3e572c 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -15,6 +15,7 @@
 #include <linux/firmware.h>
 #include <linux/jiffies.h>
 #include <linux/mdio.h>
+#include <linux/pci.h>
 #include <linux/phy.h>
 #include <linux/refcount.h>
 #include <linux/sched.h>
diff --git a/rust/helpers.c b/rust/helpers.c
index ab39c0a81c7a..319371440d43 100644
--- a/rust/helpers.c
+++ b/rust/helpers.c
@@ -30,6 +30,7 @@
 #include <linux/highmem.h>
 #include <linux/io.h>
 #include <linux/mutex.h>
+#include <linux/pci.h>
 #include <linux/rcupdate.h>
 #include <linux/refcount.h>
 #include <linux/sched/signal.h>
@@ -327,6 +328,23 @@ int rust_helper_devm_add_action(struct device *dev, void (*action)(void *), void
 }
 EXPORT_SYMBOL_GPL(rust_helper_devm_add_action);
 
+void rust_helper_pci_set_drvdata(struct pci_dev *pdev, void *data)
+{
+	pci_set_drvdata(pdev, data);
+}
+EXPORT_SYMBOL_GPL(rust_helper_pci_set_drvdata);
+
+void *rust_helper_pci_get_drvdata(struct pci_dev *pdev)
+{
+	return pci_get_drvdata(pdev);
+}
+EXPORT_SYMBOL_GPL(rust_helper_pci_get_drvdata);
+
+u64 rust_helper_pci_resource_len(struct pci_dev *pdev, int barnr)
+{
+	return pci_resource_len(pdev, barnr);
+}
+
 /*
  * `bindgen` binds the C `size_t` type as the Rust `usize` type, so we can
  * use it in contexts where Rust expects a `usize` like slice (array) indices.
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 0ca96775c5b5..1649c7060597 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -63,6 +63,8 @@ pub mod workqueue;
 pub use bindings;
 pub mod io;
 pub use macros;
+#[cfg(all(CONFIG_PCI, CONFIG_PCI_MSI))]
+pub mod pci;
 pub use uapi;
 
 #[doc(hidden)]
diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
new file mode 100644
index 000000000000..a8230474e9b8
--- /dev/null
+++ b/rust/kernel/pci.rs
@@ -0,0 +1,325 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Wrappers for the PCI subsystem
+//!
+//! C header: [`include/linux/pci.h`](srctree/include/linux/pci.h)
+
+use crate::{
+    bindings, container_of, device,
+    device_id::{IdTable, RawDeviceId},
+    driver,
+    error::{to_result, Result},
+    str::CStr,
+    types::{ARef, ForeignOwnable},
+    ThisModule,
+};
+use kernel::prelude::*; // for pinned_drop
+
+/// An adapter for the registration of PCI drivers.
+pub struct Adapter<T: Driver>(T);
+
+impl<T: Driver> driver::DriverOps for Adapter<T> {
+    type RegType = bindings::pci_driver;
+
+    fn register(
+        pdrv: &mut Self::RegType,
+        name: &'static CStr,
+        module: &'static ThisModule,
+    ) -> Result {
+        pdrv.name = name.as_char_ptr();
+        pdrv.probe = Some(Self::probe_callback);
+        pdrv.remove = Some(Self::remove_callback);
+        pdrv.id_table = T::ID_TABLE.as_ref();
+
+        // SAFETY: `pdrv` is guaranteed to be a valid `RegType`.
+        to_result(unsafe {
+            bindings::__pci_register_driver(pdrv as _, module.0, name.as_char_ptr())
+        })
+    }
+
+    fn unregister(pdrv: &mut Self::RegType) {
+        // SAFETY: `pdrv` is guaranteed to be a valid `RegType`.
+        unsafe { bindings::pci_unregister_driver(pdrv) }
+    }
+}
+
+impl<T: Driver> Adapter<T> {
+    extern "C" fn probe_callback(
+        pdev: *mut bindings::pci_dev,
+        id: *const bindings::pci_device_id,
+    ) -> core::ffi::c_int {
+        // SAFETY: Safe because the core kernel only ever calls the probe callback with a valid
+        // `pdev`.
+        let dev = unsafe { device::Device::from_raw(&mut (*pdev).dev) };
+        // SAFETY: Guaranteed by the rules described above.
+        let mut pdev = unsafe { Device::from_dev(dev) };
+
+        // SAFETY: `id` is a pointer within the static table, so it's always valid.
+        let offset = unsafe { (*id).driver_data };
+        let info = {
+            // SAFETY: The offset comes from a previous call to `offset_from` in `IdArray::new`,
+            // which guarantees that the resulting pointer is within the table.
+            let ptr = unsafe {
+                id.cast::<u8>()
+                    .offset(offset as _)
+                    .cast::<Option<T::IdInfo>>()
+            };
+            // SAFETY: Guaranteed by the preceding safety requirement.
+            unsafe { (*ptr).as_ref() }
+        };
+        match T::probe(&mut pdev, info) {
+            Ok(data) => {
+                // Let the `struct pci_dev` own a reference of the driver's private data.
+                // SAFETY: The core kernel only ever calls the probe callback with a valid `pdev`.
+                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 core kernel only ever calls the probe callback with a valid `pdev`. `ptr`
+        // points to a valid reference of the driver's private data, as it was set by
+        // `Adapter::probe_callback`.
+        let data = unsafe {
+            let ptr = bindings::pci_get_drvdata(pdev);
+
+            T::Data::from_foreign(ptr)
+        };
+
+        T::remove(&data);
+    }
+}
+
+/// Declares a kernel module that exposes a single PCI driver.
+///
+/// # Example
+///
+///```ignore
+/// kernel::module_pci_driver! {
+///     type: MyDriver,
+///     name: "Module name",
+///     author: "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.
+#[derive(Clone, Copy)]
+pub struct DeviceId {
+    /// Vendor ID
+    pub vendor: u32,
+    /// Device ID
+    pub device: u32,
+    /// Subsystem vendor ID
+    pub subvendor: u32,
+    /// Subsystem device ID
+    pub subdevice: u32,
+    /// Device class and subclass
+    pub class: u32,
+    /// Limit which sub-fields of the class
+    pub class_mask: u32,
+}
+
+impl DeviceId {
+    const PCI_ANY_ID: u32 = !0;
+
+    /// PCI_DEVICE macro.
+    pub const fn new(vendor: u32, device: u32) -> Self {
+        Self {
+            vendor,
+            device,
+            subvendor: DeviceId::PCI_ANY_ID,
+            subdevice: DeviceId::PCI_ANY_ID,
+            class: 0,
+            class_mask: 0,
+        }
+    }
+
+    /// PCI_DEVICE_CLASS macro.
+    pub const fn with_class(class: u32, class_mask: u32) -> Self {
+        Self {
+            vendor: DeviceId::PCI_ANY_ID,
+            device: DeviceId::PCI_ANY_ID,
+            subvendor: DeviceId::PCI_ANY_ID,
+            subdevice: DeviceId::PCI_ANY_ID,
+            class,
+            class_mask,
+        }
+    }
+
+    /// PCI_DEVICE_ID macro.
+    pub const fn to_rawid(&self, offset: isize) -> bindings::pci_device_id {
+        bindings::pci_device_id {
+            vendor: self.vendor,
+            device: self.device,
+            subvendor: self.subvendor,
+            subdevice: self.subdevice,
+            class: self.class,
+            class_mask: self.class_mask,
+            driver_data: offset as _,
+            override_only: 0,
+        }
+    }
+}
+
+// SAFETY: `ZERO` is all zeroed-out and `to_rawid` stores `offset` in `pci_device_id::driver_data`.
+unsafe impl RawDeviceId for DeviceId {
+    type RawType = bindings::pci_device_id;
+
+    const ZERO: Self::RawType = bindings::pci_device_id {
+        vendor: 0,
+        device: 0,
+        subvendor: 0,
+        subdevice: 0,
+        class: 0,
+        class_mask: 0,
+        driver_data: 0,
+        override_only: 0,
+    };
+}
+
+/// Define a const pci device id table
+///
+/// # Examples
+///
+/// See [`Driver`]
+///
+#[macro_export]
+macro_rules! define_pci_id_table {
+    ($data_type:ty, $($t:tt)*) => {
+        type IdInfo = $data_type;
+        const ID_TABLE: $crate::device_id::IdTable<'static, $crate::pci::DeviceId, $data_type> = {
+            $crate::define_id_array!(ARRAY, $crate::pci::DeviceId, $data_type, $($t)* );
+            ARRAY.as_table()
+        };
+    };
+}
+pub use define_pci_id_table;
+
+/// The PCI driver trait.
+///
+/// # Example
+///
+///```
+/// # use kernel::{bindings, define_pci_id_table, pci, sync::Arc};
+///
+/// struct MyDriver;
+/// struct MyDeviceData;
+///
+/// impl pci::Driver for MyDriver {
+///     type Data = Arc<MyDeviceData>;
+///
+///     define_pci_id_table! {
+///         (),
+///         [ (pci::DeviceId::new(bindings::PCI_VENDOR_ID_REDHAT,
+///                               bindings::PCI_ANY_ID as u32),
+///            None)
+///         ]
+///     }
+///
+///     fn probe(
+///         _pdev: &mut pci::Device,
+///         _id_info: Option<&Self::IdInfo>
+///     ) -> Result<Self::Data> {
+///         Err(ENODEV)
+///     }
+///
+///     fn remove(_data: &Self::Data) {
+///     }
+/// }
+///```
+/// 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 {
+    /// Data stored on device by driver.
+    ///
+    /// Corresponds to the data set or retrieved via the kernel's
+    /// `pci_{set,get}_drvdata()` functions.
+    ///
+    /// Require that `Data` implements `ForeignOwnable`. We guarantee to
+    /// never move the underlying wrapped data structure.
+    ///
+    /// TODO: Use associated_type_defaults once stabilized:
+    ///
+    /// `type Data: ForeignOwnable = ();`
+    type Data: ForeignOwnable;
+
+    /// 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<'static, DeviceId, 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: &mut Device, id: Option<&Self::IdInfo>) -> Result<Self::Data>;
+
+    /// PCI driver remove.
+    ///
+    /// Called when a platform device is removed.
+    /// Implementers should prepare the device for complete removal here.
+    fn remove(data: &Self::Data);
+}
+
+/// The PCI device representation.
+///
+/// A PCI device is based on an always reference counted `device:Device` instance. Cloning a PCI
+/// device, hence, also increments the base device' reference count.
+#[derive(Clone)]
+pub struct Device(ARef<device::Device>);
+
+impl Device {
+    /// Create a PCI Device instance from an existing `device::Device`.
+    ///
+    /// # Safety
+    ///
+    /// `dev` must be an `ARef<device::Device>` whose underlying `bindings::device` is a member of
+    /// a `bindings::pci_dev`.
+    pub unsafe fn from_dev(dev: ARef<device::Device>) -> Self {
+        Self(dev)
+    }
+
+    fn as_raw(&self) -> *mut bindings::pci_dev {
+        // SAFETY: Guaranteed by the type invaraints.
+        unsafe { container_of!(self.0.as_raw(), bindings::pci_dev, dev) as _ }
+    }
+
+    /// Enable the Device's memory.
+    pub fn enable_device_mem(&self) -> Result {
+        // SAFETY: Safe by the type invariants.
+        let ret = unsafe { bindings::pci_enable_device_mem(self.as_raw()) };
+        if ret != 0 {
+            Err(Error::from_errno(ret))
+        } else {
+            Ok(())
+        }
+    }
+
+    /// Set the Device's master.
+    pub fn set_master(&self) {
+        // SAFETY: Safe by the type invariants.
+        unsafe { bindings::pci_set_master(self.as_raw()) };
+    }
+}
+
+impl AsRef<device::Device> for Device {
+    fn as_ref(&self) -> &device::Device {
+        &self.0
+    }
+}