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-rw-r--r--Documentation/rust/coding-guidelines.rst75
-rw-r--r--rust/kernel/alloc/kvec.rs2
-rw-r--r--rust/kernel/bitmap.rs8
-rw-r--r--rust/kernel/cpufreq.rs3
4 files changed, 83 insertions, 5 deletions
diff --git a/Documentation/rust/coding-guidelines.rst b/Documentation/rust/coding-guidelines.rst
index 6ff9e754755d..3198be3a6d63 100644
--- a/Documentation/rust/coding-guidelines.rst
+++ b/Documentation/rust/coding-guidelines.rst
@@ -38,6 +38,81 @@ Like ``clang-format`` for the rest of the kernel, ``rustfmt`` works on
individual files, and does not require a kernel configuration. Sometimes it may
even work with broken code.
+Imports
+~~~~~~~
+
+``rustfmt``, by default, formats imports in a way that is prone to conflicts
+while merging and rebasing, since in some cases it condenses several items into
+the same line. For instance:
+
+.. code-block:: rust
+
+ // Do not use this style.
+ use crate::{
+ example1,
+ example2::{example3, example4, example5},
+ example6, example7,
+ example8::example9,
+ };
+
+Instead, the kernel uses a vertical layout that looks like this:
+
+.. code-block:: rust
+
+ use crate::{
+ example1,
+ example2::{
+ example3,
+ example4,
+ example5, //
+ },
+ example6,
+ example7,
+ example8::example9, //
+ };
+
+That is, each item goes into its own line, and braces are used as soon as there
+is more than one item in a list.
+
+The trailing empty comment allows to preserve this formatting. Not only that,
+``rustfmt`` will actually reformat imports vertically when the empty comment is
+added. That is, it is possible to easily reformat the original example into the
+expected style by running ``rustfmt`` on an input like:
+
+.. code-block:: rust
+
+ // Do not use this style.
+ use crate::{
+ example1,
+ example2::{example3, example4, example5, //
+ },
+ example6, example7,
+ example8::example9, //
+ };
+
+The trailing empty comment works for nested imports, as shown above, as well as
+for single item imports -- this can be useful to minimize diffs within patch
+series:
+
+.. code-block:: rust
+
+ use crate::{
+ example1, //
+ };
+
+The trailing empty comment works in any of the lines within the braces, but it
+is preferred to keep it in the last item, since it is reminiscent of the
+trailing comma in other formatters. Sometimes it may be simpler to avoid moving
+the comment several times within a patch series due to changes in the list.
+
+There may be cases where exceptions may need to be made, i.e. none of this is
+a hard rule. There is also code that is not migrated to this style yet, but
+please do not introduce code in other styles.
+
+Eventually, the goal is to get ``rustfmt`` to support this formatting style (or
+a similar one) automatically in a stable release without requiring the trailing
+empty comment. Thus, at some point, the goal is to remove those comments.
+
Comments
--------
diff --git a/rust/kernel/alloc/kvec.rs b/rust/kernel/alloc/kvec.rs
index e94aebd084c8..ac8d6f763ae8 100644
--- a/rust/kernel/alloc/kvec.rs
+++ b/rust/kernel/alloc/kvec.rs
@@ -9,7 +9,7 @@ use super::{
};
use crate::{
fmt,
- page::AsPageIter,
+ page::AsPageIter, //
};
use core::{
borrow::{Borrow, BorrowMut},
diff --git a/rust/kernel/bitmap.rs b/rust/kernel/bitmap.rs
index 711b8368b38f..aa8fc7bf06fc 100644
--- a/rust/kernel/bitmap.rs
+++ b/rust/kernel/bitmap.rs
@@ -167,7 +167,9 @@ impl core::ops::Deref for BitmapVec {
let ptr = if self.nbits <= BITS_PER_LONG {
// SAFETY: Bitmap is represented inline.
#[allow(unused_unsafe, reason = "Safe since Rust 1.92.0")]
- unsafe { core::ptr::addr_of!(self.repr.bitmap) }
+ unsafe {
+ core::ptr::addr_of!(self.repr.bitmap)
+ }
} else {
// SAFETY: Bitmap is represented as array of `unsigned long`.
unsafe { self.repr.ptr.as_ptr() }
@@ -184,7 +186,9 @@ impl core::ops::DerefMut for BitmapVec {
let ptr = if self.nbits <= BITS_PER_LONG {
// SAFETY: Bitmap is represented inline.
#[allow(unused_unsafe, reason = "Safe since Rust 1.92.0")]
- unsafe { core::ptr::addr_of_mut!(self.repr.bitmap) }
+ unsafe {
+ core::ptr::addr_of_mut!(self.repr.bitmap)
+ }
} else {
// SAFETY: Bitmap is represented as array of `unsigned long`.
unsafe { self.repr.ptr.as_ptr() }
diff --git a/rust/kernel/cpufreq.rs b/rust/kernel/cpufreq.rs
index 21b5b9b8acc1..1a555fcb120a 100644
--- a/rust/kernel/cpufreq.rs
+++ b/rust/kernel/cpufreq.rs
@@ -38,8 +38,7 @@ use macros::vtable;
const CPUFREQ_NAME_LEN: usize = bindings::CPUFREQ_NAME_LEN as usize;
/// Default transition latency value in nanoseconds.
-pub const DEFAULT_TRANSITION_LATENCY_NS: u32 =
- bindings::CPUFREQ_DEFAULT_TRANSITION_LATENCY_NS;
+pub const DEFAULT_TRANSITION_LATENCY_NS: u32 = bindings::CPUFREQ_DEFAULT_TRANSITION_LATENCY_NS;
/// CPU frequency driver flags.
pub mod flags {