Revert "FROMLIST: rust: miscdevice: add mmap support"

This reverts commit 88a4dfa30b.

Bug: 429146594
Change-Id: Ia75f9f7f9706971fe47e6ab74a8f0009876396af
Signed-off-by: Alice Ryhl <aliceryhl@google.com>

rust/kernel/miscdevice.rs

@@ -14,7 +14,6 @@ use crate::{
     error::{to_result, Error, Result, VTABLE_DEFAULT_ERROR},
     ffi::{c_int, c_long, c_uint, c_ulong, c_void},
     fs::{File, LocalFile},
-    mm::virt::VmAreaNew,
     prelude::*,
     seq_file::SeqFile,
     str::CStr,
@@ -124,22 +123,6 @@ pub trait MiscDevice: Sized {
         drop(device);
     }
 
-    /// Handle for mmap.
-    ///
-    /// This function is invoked when a user space process invokes the `mmap` system call on
-    /// `file`. The function is a callback that is part of the VMA initializer. The kernel will do
-    /// initial setup of the VMA before calling this function. The function can then interact with
-    /// the VMA initialization by calling methods of `vma`. If the function does not return an
-    /// error, the kernel will complete initialization of the VMA according to the properties of
-    /// `vma`.
-    fn mmap(
-        _device: <Self::Ptr as ForeignOwnable>::Borrowed<'_>,
-        _file: &File,
-        _vma: &VmAreaNew,
-    ) -> Result {
-        kernel::build_error!(VTABLE_DEFAULT_ERROR)
-    }
-
     /// Seeks this miscdevice.
     fn llseek(
         _device: <Self::Ptr as ForeignOwnable>::Borrowed<'_>,
@@ -286,7 +269,6 @@ const fn create_vtable<T: MiscDevice>() -> &'static bindings::file_operations {
         const VTABLE: bindings::file_operations = bindings::file_operations {
             open: Some(fops_open::<T>),
             release: Some(fops_release::<T>),
-            mmap: maybe_fn(T::HAS_MMAP, fops_mmap::<T>),
             llseek: maybe_fn(T::HAS_LLSEEK, fops_llseek::<T>),
             read_iter: maybe_fn(T::HAS_READ_ITER, fops_read_iter::<T>),
             write_iter: maybe_fn(T::HAS_WRITE_ITER, fops_write_iter::<T>),
@@ -371,32 +353,6 @@ unsafe extern "C" fn fops_release<T: MiscDevice>(
     0
 }
 
-/// # Safety
-///
-/// `file` must be a valid file that is associated with a `MiscDeviceRegistration<T>`.
-/// `vma` must be a vma that is currently being mmap'ed with this file.
-unsafe extern "C" fn fops_mmap<T: MiscDevice>(
-    file: *mut bindings::file,
-    vma: *mut bindings::vm_area_struct,
-) -> c_int {
-    // SAFETY: The mmap call of a file can access the private data.
-    let private = unsafe { (*file).private_data };
-    // SAFETY: This is a Rust Miscdevice, so we call `into_foreign` in `open` and `from_foreign` in
-    // `release`, and `fops_mmap` is guaranteed to be called between those two operations.
-    let device = unsafe { <T::Ptr as ForeignOwnable>::borrow(private) };
-    // SAFETY: The caller provides a vma that is undergoing initial VMA setup.
-    let area = unsafe { VmAreaNew::from_raw(vma) };
-    // 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::mmap(device, file, area) {
-        Ok(()) => 0,
-        Err(err) => err.to_errno() as c_int,
-    }
-}
-
 /// # Safety
 ///
 /// `file` must be a valid file that is associated with a `MiscDeviceRegistration<T>`.