Return a SimpleFileSystem from BootServices::get_image_file_system

This reverts a small change from: rust-osdev#472

If using the library without the `alloc` feature enabled, `FileSystem` isn't
available, but you might still want access to the image's file system via the
underlying protocol.

The high-level API is still easily accessible via `FileSystem::new`.

Author: nicholasbishop

CHANGELOG.md

@@ -5,6 +5,8 @@
 ### Changed
 - `Input::wait_for_key_event` now returns an `Option<Event>`, and is no longer `const`.
 - `LoadedImage::device` now returns an `Option<Handle>` and is no longer `const`.
+- `BootServices::get_image_file_system` now returns
+  `ScopedProtocol<SimpleFileSystem>` instead of `fs::FileSystem`.
 
 ## uefi-macros - [Unreleased]
 

uefi-test-runner/src/boot/mod.rs

@@ -1,4 +1,5 @@
 use alloc::string::ToString;
+use uefi::fs::FileSystem;
 use uefi::proto::console::text::Output;
 use uefi::proto::device_path::media::FilePath;
 use uefi::proto::device_path::{DevicePath, LoadedImageDevicePath};
@@ -76,11 +77,13 @@ fn test_load_image(bt: &BootServices) {
 
     // Variant A: FromBuffer
     {
-        let mut fs = bt
+        let fs = bt
             .get_image_file_system(bt.image_handle())
             .expect("should open file system");
         let path = CString16::try_from(image_device_path_file_path.as_str()).unwrap();
-        let image_data = fs.read(&*path).expect("should read file content");
+        let image_data = FileSystem::new(fs)
+            .read(&*path)
+            .expect("should read file content");
         let load_source = LoadImageSource::FromBuffer {
             buffer: image_data.as_slice(),
             file_path: None,

uefi/src/table/boot.rs

@@ -3,6 +3,8 @@
 use super::Revision;
 use crate::data_types::{Align, PhysicalAddress};
 use crate::proto::device_path::DevicePath;
+use crate::proto::loaded_image::LoadedImage;
+use crate::proto::media::fs::SimpleFileSystem;
 use crate::proto::{Protocol, ProtocolPointer};
 use crate::{Char16, Error, Event, Guid, Handle, Result, Status, StatusExt};
 use core::cell::UnsafeCell;
@@ -12,12 +14,9 @@ use core::mem::{self, MaybeUninit};
 use core::ops::{Deref, DerefMut};
 use core::ptr::NonNull;
 use core::{ptr, slice};
+
 #[cfg(feature = "alloc")]
-use {
-    crate::fs::FileSystem,
-    crate::proto::{loaded_image::LoadedImage, media::fs::SimpleFileSystem},
-    ::alloc::vec::Vec,
-};
+use alloc::vec::Vec;
 
 pub use uefi_raw::table::boot::{
     EventType, InterfaceType, MemoryAttribute, MemoryDescriptor, MemoryType, Tpl,
@@ -1344,6 +1343,38 @@ impl BootServices {
     pub unsafe fn set_mem(&self, buffer: *mut u8, size: usize, value: u8) {
         (self.0.set_mem)(buffer, size, value);
     }
+
+    /// Retrieves a [`SimpleFileSystem`] protocol associated with the device the given
+    /// image was loaded from.
+    ///
+    /// # Errors
+    ///
+    /// This function can return errors from [`open_protocol_exclusive`] and
+    /// [`locate_device_path`]. See those functions for more details.
+    ///
+    /// [`open_protocol_exclusive`]: Self::open_protocol_exclusive
+    /// [`locate_device_path`]: Self::locate_device_path
+    ///
+    /// * [`uefi::Status::INVALID_PARAMETER`]
+    /// * [`uefi::Status::UNSUPPORTED`]
+    /// * [`uefi::Status::ACCESS_DENIED`]
+    /// * [`uefi::Status::ALREADY_STARTED`]
+    /// * [`uefi::Status::NOT_FOUND`]
+    pub fn get_image_file_system(
+        &self,
+        image_handle: Handle,
+    ) -> Result<ScopedProtocol<SimpleFileSystem>> {
+        let loaded_image = self.open_protocol_exclusive::<LoadedImage>(image_handle)?;
+
+        let device_handle = loaded_image
+            .device()
+            .ok_or(Error::new(Status::UNSUPPORTED, ()))?;
+        let device_path = self.open_protocol_exclusive::<DevicePath>(device_handle)?;
+
+        let device_handle = self.locate_device_path::<SimpleFileSystem>(&mut &*device_path)?;
+
+        self.open_protocol_exclusive(device_handle)
+    }
 }
 
 #[cfg(feature = "alloc")]
@@ -1377,37 +1408,6 @@ impl BootServices {
         // Emit output, with warnings
         Ok(handles)
     }
-
-    /// Retrieves a [`FileSystem`] protocol associated with the device the given
-    /// image was loaded from.
-    ///
-    /// # Errors
-    ///
-    /// This function can return errors from [`open_protocol_exclusive`] and
-    /// [`locate_device_path`]. See those functions for more details.
-    ///
-    /// [`open_protocol_exclusive`]: Self::open_protocol_exclusive
-    /// [`locate_device_path`]: Self::locate_device_path
-    /// [`FileSystem`]: uefi::fs::FileSystem
-    ///
-    /// * [`uefi::Status::INVALID_PARAMETER`]
-    /// * [`uefi::Status::UNSUPPORTED`]
-    /// * [`uefi::Status::ACCESS_DENIED`]
-    /// * [`uefi::Status::ALREADY_STARTED`]
-    /// * [`uefi::Status::NOT_FOUND`]
-    pub fn get_image_file_system(&self, image_handle: Handle) -> Result<FileSystem> {
-        let loaded_image = self.open_protocol_exclusive::<LoadedImage>(image_handle)?;
-
-        let device_handle = loaded_image
-            .device()
-            .ok_or(Error::new(Status::UNSUPPORTED, ()))?;
-        let device_path = self.open_protocol_exclusive::<DevicePath>(device_handle)?;
-
-        let device_handle = self.locate_device_path::<SimpleFileSystem>(&mut &*device_path)?;
-
-        let protocol = self.open_protocol_exclusive(device_handle)?;
-        Ok(FileSystem::new(protocol))
-    }
 }
 
 impl super::Table for BootServices {