// SPDX-License-Identifier: GPL-2.0 // Copyright (C) 2024 Google LLC. //! Miscdevice support.//!//! C headers: [`include/linux/miscdevice.h`](srctree/include/linux/miscdevice.h).//!//! Reference: <https://www.kernel.org/doc/html/latest/driver-api/misc_devices.html> use crate::{    bindings,    device::Device,    error::{to_result, Error, Result, VTABLE_DEFAULT_ERROR},    ffi::{c_int, c_long, c_uint, c_ulong},    fs::File,    prelude::*,    seq_file::SeqFile,    str::CStr,    types::{ForeignOwnable, Opaque},};use core::{marker::PhantomData, mem::MaybeUninit, pin::Pin}; /// Options for creating a misc device.#[derive(Copy, Clone)]pub struct MiscDeviceOptions {    /// The name of the miscdevice.    pub name: &'static CStr,} impl MiscDeviceOptions {    /// Create a raw `struct miscdev` ready for registration.    pub const fn into_raw<T: MiscDevice>(self) -> bindings::miscdevice {        // SAFETY: All zeros is valid for this C type.        let mut result: bindings::miscdevice = unsafe { MaybeUninit::zeroed().assume_init() };        result.minor = bindings::MISC_DYNAMIC_MINOR as _;        result.name = self.name.as_char_ptr();        result.fops = create_vtable::<T>();        result    }} /// A registration of a miscdevice.////// # Invariants////// `inner` is a registered misc device.#[repr(transparent)]#[pin_data(PinnedDrop)]pub struct MiscDeviceRegistration<T> {    #[pin]    inner: Opaque<bindings::miscdevice>,    _t: PhantomData<T>,} // SAFETY: It is allowed to call `misc_deregister` on a different thread from where you called// `misc_register`.unsafe impl<T> Send for MiscDeviceRegistration<T> {}// SAFETY: All `&self` methods on this type are written to ensure that it is safe to call them in// parallel.unsafe impl<T> Sync for MiscDeviceRegistration<T> {} impl<T: MiscDevice> MiscDeviceRegistration<T> {    /// Register a misc device.    pub fn register(opts: MiscDeviceOptions) -> impl PinInit<Self, Error> {        try_pin_init!(Self {            inner <- Opaque::try_ffi_init(move |slot: *mut bindings::miscdevice| {                // SAFETY: The initializer can write to the provided `slot`.                unsafe { slot.write(opts.into_raw::<T>()) };                 // SAFETY: We just wrote the misc device options to the slot. The miscdevice will                // get unregistered before `slot` is deallocated because the memory is pinned and                // the destructor of this type deallocates the memory.                // INVARIANT: If this returns `Ok(())`, then the `slot` will contain a registered                // misc device.                to_result(unsafe { bindings::misc_register(slot) })            }),            _t: PhantomData,        })    }     /// Returns a raw pointer to the misc device.    pub fn as_raw(&self) -> *mut bindings::miscdevice {        self.inner.get()    }     /// Access the `this_device` field.    pub fn device(&self) -> &Device {        // SAFETY: This can only be called after a successful register(), which always        // initialises `this_device` with a valid device. Furthermore, the signature of this        // function tells the borrow-checker that the `&Device` reference must not outlive the        // `&MiscDeviceRegistration<T>` used to obtain it, so the last use of the reference must be        // before the underlying `struct miscdevice` is destroyed.        unsafe { Device::as_ref((*self.as_raw()).this_device) }    }} #[pinned_drop]impl<T> PinnedDrop for MiscDeviceRegistration<T> {    fn drop(self: Pin<&mut Self>) {        // SAFETY: We know that the device is registered by the type invariants.        unsafe { bindings::misc_deregister(self.inner.get()) };    }} /// Trait implemented by the private data of an open misc device.#[vtable]pub trait MiscDevice: Sized {    /// What kind of pointer should `Self` be wrapped in.    type Ptr: ForeignOwnable + Send + Sync;     /// Called when the misc device is opened.    ///    /// The returned pointer will be stored as the private data for the file.    fn open(_file: &File, _misc: &MiscDeviceRegistration<Self>) -> Result<Self::Ptr>;     /// Called when the misc device is released.    fn release(device: Self::Ptr, _file: &File) {        drop(device);    }     /// Handler for ioctls.    ///    /// The `cmd` argument is usually manipulated using the utilties in [`kernel::ioctl`].    ///    /// [`kernel::ioctl`]: mod@crate::ioctl    fn ioctl(        _device: <Self::Ptr as ForeignOwnable>::Borrowed<'_>,        _file: &File,        _cmd: u32,        _arg: usize,    ) -> Result<isize> {        build_error!(VTABLE_DEFAULT_ERROR)    }     /// Handler for ioctls.    ///    /// Used for 32-bit userspace on 64-bit platforms.    ///    /// This method is optional and only needs to be provided if the ioctl relies on structures    /// that have different layout on 32-bit and 64-bit userspace. If no implementation is    /// provided, then `compat_ptr_ioctl` will be used instead.    #[cfg(CONFIG_COMPAT)]    fn compat_ioctl(        _device: <Self::Ptr as ForeignOwnable>::Borrowed<'_>,        _file: &File,        _cmd: u32,        _arg: usize,    ) -> Result<isize> {        build_error!(VTABLE_DEFAULT_ERROR)    }     /// Show info for this fd.    fn show_fdinfo(        _device: <Self::Ptr as ForeignOwnable>::Borrowed<'_>,        _m: &SeqFile,        _file: &File,    ) {        build_error!(VTABLE_DEFAULT_ERROR)    }} const fn create_vtable<T: MiscDevice>() -> &'static bindings::file_operations {    const fn maybe_fn<T: Copy>(check: bool, func: T) -> Option<T> {        if check {            Some(func)        } else {            None        }    }     struct VtableHelper<T: MiscDevice> {        _t: PhantomData<T>,    }    impl<T: MiscDevice> VtableHelper<T> {        const VTABLE: bindings::file_operations = bindings::file_operations {            open: Some(fops_open::<T>),            release: Some(fops_release::<T>),            unlocked_ioctl: maybe_fn(T::HAS_IOCTL, fops_ioctl::<T>),            #[cfg(CONFIG_COMPAT)]            compat_ioctl: if T::HAS_COMPAT_IOCTL {                Some(fops_compat_ioctl::<T>)            } else if T::HAS_IOCTL {                Some(bindings::compat_ptr_ioctl)            } else {                None            },            show_fdinfo: maybe_fn(T::HAS_SHOW_FDINFO, fops_show_fdinfo::<T>),            // SAFETY: All zeros is a valid value for `bindings::file_operations`.            ..unsafe { MaybeUninit::zeroed().assume_init() }        };    }     &VtableHelper::<T>::VTABLE} /// # Safety////// `file` and `inode` must be the file and inode for a file that is undergoing initialization./// The file must be associated with a `MiscDeviceRegistration<T>`.unsafe extern "C" fn fops_open<T: MiscDevice>(    inode: *mut bindings::inode,    raw_file: *mut bindings::file,) -> c_int {    // SAFETY: The pointers are valid and for a file being opened.    let ret = unsafe { bindings::generic_file_open(inode, raw_file) };    if ret != 0 {        return ret;    }     // SAFETY: The open call of a file can access the private data.    let misc_ptr = unsafe { (*raw_file).private_data };     // SAFETY: This is a miscdevice, so `misc_open()` set the private data to a pointer to the    // associated `struct miscdevice` before calling into this method. Furthermore, `misc_open()`    // ensures that the miscdevice can't be unregistered and freed during this call to `fops_open`.    let misc = unsafe { &*misc_ptr.cast::<MiscDeviceRegistration<T>>() };     // SAFETY:    // * This underlying file is valid for (much longer than) the duration of `T::open`.    // * There is no active fdget_pos region on the file on this thread.    let file = unsafe { File::from_raw_file(raw_file) };     let ptr = match T::open(file, misc) {        Ok(ptr) => ptr,        Err(err) => return err.to_errno(),    };     // This overwrites the private data with the value specified by the user, changing the type of    // this file's private data. All future accesses to the private data is performed by other    // fops_* methods in this file, which all correctly cast the private data to the new type.    //    // SAFETY: The open call of a file can access the private data.    unsafe { (*raw_file).private_data = ptr.into_foreign() };     0} /// # Safety////// `file` and `inode` must be the file and inode for a file that is being released. The file must/// be associated with a `MiscDeviceRegistration<T>`.unsafe extern "C" fn fops_release<T: MiscDevice>(    _inode: *mut bindings::inode,    file: *mut bindings::file,) -> c_int {    // SAFETY: The release call of a file owns the private data.    let private = unsafe { (*file).private_data };    // SAFETY: The release call of a file owns the private data.    let ptr = unsafe { <T::Ptr as ForeignOwnable>::from_foreign(private) };     // SAFETY:    // * The file is valid for the duration of this call.    // * There is no active fdget_pos region on the file on this thread.    T::release(ptr, unsafe { File::from_raw_file(file) });     0} /// # Safety////// `file` must be a valid file that is associated with a `MiscDeviceRegistration<T>`.unsafe extern "C" fn fops_ioctl<T: MiscDevice>(    file: *mut bindings::file,    cmd: c_uint,    arg: c_ulong,) -> c_long {    // SAFETY: The ioctl call of a file can access the private data.    let private = unsafe { (*file).private_data };    // SAFETY: Ioctl calls can borrow the private data of the file.    let device = unsafe { <T::Ptr as ForeignOwnable>::borrow(private) };     // SAFETY:    // * The file is valid for the duration of this call.    // * There is no active fdget_pos region on the file on this thread.    let file = unsafe { File::from_raw_file(file) };     match T::ioctl(device, file, cmd, arg) {        Ok(ret) => ret as c_long,        Err(err) => err.to_errno() as c_long,    }} /// # Safety////// `file` must be a valid file that is associated with a `MiscDeviceRegistration<T>`.#[cfg(CONFIG_COMPAT)]unsafe extern "C" fn fops_compat_ioctl<T: MiscDevice>(    file: *mut bindings::file,    cmd: c_uint,    arg: c_ulong,) -> c_long {    // SAFETY: The compat ioctl call of a file can access the private data.    let private = unsafe { (*file).private_data };    // SAFETY: Ioctl calls can borrow the private data of the file.    let device = unsafe { <T::Ptr as ForeignOwnable>::borrow(private) };     // SAFETY:    // * The file is valid for the duration of this call.    // * There is no active fdget_pos region on the file on this thread.    let file = unsafe { File::from_raw_file(file) };     match T::compat_ioctl(device, file, cmd, arg) {        Ok(ret) => ret as c_long,        Err(err) => err.to_errno() as c_long,    }} /// # Safety////// - `file` must be a valid file that is associated with a `MiscDeviceRegistration<T>`./// - `seq_file` must be a valid `struct seq_file` that we can write to.unsafe extern "C" fn fops_show_fdinfo<T: MiscDevice>(    seq_file: *mut bindings::seq_file,    file: *mut bindings::file,) {    // SAFETY: The release call of a file owns the private data.    let private = unsafe { (*file).private_data };    // SAFETY: Ioctl calls can borrow the private data of the file.    let device = unsafe { <T::Ptr as ForeignOwnable>::borrow(private) };    // SAFETY:    // * The file is valid for the duration of this call.    // * There is no active fdget_pos region on the file on this thread.    let file = unsafe { File::from_raw_file(file) };    // SAFETY: The caller ensures that the pointer is valid and exclusive for the duration in which    // this method is called.    let m = unsafe { SeqFile::from_raw(seq_file) };     T::show_fdinfo(device, m, file);}