rust: Inline format args

A minor Rust cleanup to inline `format!("{}", foo)` and similar macro calls into `format!("{foo}")`.

While mostly cosmetic, this change makes it a bit easier to read format argument strings, shortens code, and makes it easier to see cases with double-referencing values causing minor performance (apparently `&foo` in a format! causes about 6% perf cost due to Rust compiler being unable to inline it due to dynamic invocation.

Author: nyurik

drivers/gpio/gpio_pl061_rust.rs

@@ -143,8 +143,7 @@ impl irq::Chip for PL061Device {
         {
             dev_err!(
                 data.dev,
-                "trying to configure line {} for both level and edge detection, choose one!\n",
-                offset
+                "trying to configure line {offset} for both level and edge detection, choose one!\n",
             );
             return Err(EINVAL);
         }
@@ -172,8 +171,7 @@ impl irq::Chip for PL061Device {
             irq_data.set_level_handler();
             dev_dbg!(
                 data.dev,
-                "line {}: IRQ on {} level\n",
-                offset,
+                "line {offset}: IRQ on {} level\n",
                 if polarity { "HIGH" } else { "LOW" }
             );
         } else if (trigger & irq::Type::EDGE_BOTH) == irq::Type::EDGE_BOTH {
@@ -182,7 +180,7 @@ impl irq::Chip for PL061Device {
             // Select both edges, settings this makes GPIOEV be ignored.
             gpioibe |= bit;
             irq_data.set_edge_handler();
-            dev_dbg!(data.dev, "line {}: IRQ on both edges\n", offset);
+            dev_dbg!(data.dev, "line {offset}: IRQ on both edges\n");
         } else if trigger & (irq::Type::EDGE_RISING | irq::Type::EDGE_FALLING) != 0 {
             let rising = trigger & irq::Type::EDGE_RISING != 0;
 
@@ -199,8 +197,7 @@ impl irq::Chip for PL061Device {
             irq_data.set_edge_handler();
             dev_dbg!(
                 data.dev,
-                "line {}: IRQ on {} edge\n",
-                offset,
+                "line {offset}: IRQ on {} edge\n",
                 if rising { "RISING" } else { "FALLING}" }
             );
         } else {
@@ -209,7 +206,7 @@ impl irq::Chip for PL061Device {
             gpioibe &= !bit;
             gpioiev &= !bit;
             irq_data.set_bad_handler();
-            dev_warn!(data.dev, "no trigger selected for line {}\n", offset);
+            dev_warn!(data.dev, "no trigger selected for line {offset}\n");
         }
 
         pl061.base.writeb(gpiois, GPIOIS);

rust/build_error.rs

@@ -27,5 +27,7 @@
 #[export_name = "rust_build_error"]
 #[track_caller]
 pub const fn build_error(msg: &'static str) -> ! {
+    // This uses const context expansion panic! special case:
+    // https://github.com/rust-lang/rust/issues/108595
     panic!("{}", msg);
 }

rust/kernel/error.rs

@@ -192,10 +192,7 @@ impl Error {
     pub(crate) fn from_kernel_errno(errno: core::ffi::c_int) -> Error {
         if errno < -(bindings::MAX_ERRNO as i32) || errno >= 0 {
             // TODO: Make it a `WARN_ONCE` once available.
-            crate::pr_warn!(
-                "attempted to create `Error` with out of range `errno`: {}",
-                errno
-            );
+            crate::pr_warn!("attempted to create `Error` with out of range `errno`: {errno}");
             return code::EINVAL;
         }
 

rust/kernel/lib.rs

@@ -254,7 +254,7 @@ macro_rules! container_of {
 #[cfg(not(any(testlib, test)))]
 #[panic_handler]
 fn panic(info: &core::panic::PanicInfo<'_>) -> ! {
-    pr_emerg!("{}\n", info);
+    pr_emerg!("{info}\n");
     // SAFETY: FFI call.
     unsafe { bindings::BUG() };
     // Bindgen currently does not recognize `__noreturn` so `BUG` returns `()`

rust/kernel/module_param.rs

@@ -399,7 +399,7 @@ impl<T: Copy, const N: usize> ArrayParam<T, { N }> {
 impl<T: core::fmt::Display, const N: usize> core::fmt::Display for ArrayParam<T, { N }> {
     fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
         for val in self.values() {
-            write!(f, "{},", val)?;
+            write!(f, "{val},")?;
         }
         Ok(())
     }
@@ -462,8 +462,8 @@ impl core::fmt::Display for StringParam {
     fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
         let bytes = self.bytes();
         match core::str::from_utf8(bytes) {
-            Ok(utf8) => write!(f, "{}", utf8),
-            Err(_) => write!(f, "{:?}", bytes),
+            Ok(utf8) => write!(f, "{utf8}"),
+            Err(_) => write!(f, "{bytes:?}"),
         }
     }
 }

rust/kernel/str.rs

@@ -209,11 +209,11 @@ impl fmt::Display for CStr {
     /// # use kernel::str::CStr;
     /// # use kernel::str::CString;
     /// let penguin = c_str!("🐧");
-    /// let s = CString::try_from_fmt(fmt!("{}", penguin)).unwrap();
+    /// let s = CString::try_from_fmt(fmt!("{penguin}")).unwrap();
     /// assert_eq!(s.as_bytes_with_nul(), "\\xf0\\x9f\\x90\\xa7\0".as_bytes());
     ///
     /// let ascii = c_str!("so \"cool\"");
-    /// let s = CString::try_from_fmt(fmt!("{}", ascii)).unwrap();
+    /// let s = CString::try_from_fmt(fmt!("{ascii}")).unwrap();
     /// assert_eq!(s.as_bytes_with_nul(), "so \"cool\"\0".as_bytes());
     /// ```
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
@@ -222,7 +222,7 @@ impl fmt::Display for CStr {
                 // Printable character.
                 f.write_char(c as char)?;
             } else {
-                write!(f, "\\x{:02x}", c)?;
+                write!(f, "\\x{c:02x}")?;
             }
         }
         Ok(())
@@ -237,12 +237,12 @@ impl fmt::Debug for CStr {
     /// # use kernel::str::CStr;
     /// # use kernel::str::CString;
     /// let penguin = c_str!("🐧");
-    /// let s = CString::try_from_fmt(fmt!("{:?}", penguin)).unwrap();
+    /// let s = CString::try_from_fmt(fmt!("{penguin:?}")).unwrap();
     /// assert_eq!(s.as_bytes_with_nul(), "\"\\xf0\\x9f\\x90\\xa7\"\0".as_bytes());
     ///
     /// // Embedded double quotes are escaped.
     /// let ascii = c_str!("so \"cool\"");
-    /// let s = CString::try_from_fmt(fmt!("{:?}", ascii)).unwrap();
+    /// let s = CString::try_from_fmt(fmt!("{ascii:?}")).unwrap();
     /// assert_eq!(s.as_bytes_with_nul(), "\"so \\\"cool\\\"\"\0".as_bytes());
     /// ```
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
@@ -252,7 +252,7 @@ impl fmt::Debug for CStr {
                 // Printable characters.
                 b'\"' => f.write_str("\\\"")?,
                 0x20..=0x7e => f.write_char(c as char)?,
-                _ => write!(f, "\\x{:02x}", c)?,
+                _ => write!(f, "\\x{c:02x}")?,
             }
         }
         f.write_str("\"")

rust/kernel/types.rs

@@ -450,7 +450,7 @@ define_unsigned_number_traits!(usize);
 ///
 /// fn print_bits(x: usize) {
 ///     for bit in bits_iter(x) {
-///         pr_info!("{}\n", bit);
+///         pr_info!("{bit}\n");
 ///     }
 /// }
 ///

rust/kernel/workqueue.rs

@@ -140,7 +140,7 @@ macro_rules! init_work_item_adapter {
 ///
 /// kernel::impl_self_work_adapter!(Example, work, |w| {
 ///     let count = w.count.fetch_add(1, Ordering::Relaxed);
-///     pr_info!("Called with count={}\n", count);
+///     pr_info!("Called with count={count}\n");
 ///
 ///     // Queue again if the count is less than 10.
 ///     if count < 10 {

rust/macros/module.rs

@@ -139,7 +139,7 @@ fn param_ops_path(param_type: &str) -> &'static str {
         "isize" => "kernel::module_param::PARAM_OPS_ISIZE",
         "usize" => "kernel::module_param::PARAM_OPS_USIZE",
         "str" => "kernel::module_param::PARAM_OPS_STR",
-        t => panic!("Unrecognized type {}", t),
+        t => panic!("Unrecognized type {t}"),
     }
 }
 
@@ -151,7 +151,7 @@ fn try_simple_param_val(
         "bool" => Box::new(try_ident),
         "str" => Box::new(|param_it| {
             try_byte_string(param_it)
-                .map(|s| format!("kernel::module_param::StringParam::Ref(b\"{}\")", s))
+                .map(|s| format!("kernel::module_param::StringParam::Ref(b\"{s}\")"))
         }),
         _ => Box::new(try_literal),
     }
@@ -247,10 +247,7 @@ impl ModuleInfo {
             };
 
             if seen_keys.contains(&key) {
-                panic!(
-                    "Duplicated key \"{}\". Keys can only be specified once.",
-                    key
-                );
+                panic!("Duplicated key \"{key}\". Keys can only be specified once.");
             }
 
             assert_eq!(expect_punct(it), ':');
@@ -266,10 +263,7 @@ impl ModuleInfo {
                     info.alias = Some(format!("rtnl-link-{}", expect_string_ascii(it)))
                 }
                 "params" => info.params = Some(expect_group(it)),
-                _ => panic!(
-                    "Unknown key \"{}\". Valid keys are: {:?}.",
-                    key, EXPECTED_KEYS
-                ),
+                _ => panic!("Unknown key \"{key}\". Valid keys are: {EXPECTED_KEYS:?}."),
             }
 
             assert_eq!(expect_punct(it), ',');
@@ -281,7 +275,7 @@ impl ModuleInfo {
 
         for key in REQUIRED_KEYS {
             if !seen_keys.iter().any(|e| e == key) {
-                panic!("Missing required key \"{}\".", key);
+                panic!("Missing required key \"{key}\".");
             }
         }
 
@@ -293,10 +287,7 @@ impl ModuleInfo {
         }
 
         if seen_keys != ordered_keys {
-            panic!(
-                "Keys are not ordered as expected. Order them like: {:?}.",
-                ordered_keys
-            );
+            panic!("Keys are not ordered as expected. Order them like: {ordered_keys:?}.");
         }
 
         info
@@ -364,7 +355,7 @@ pub(crate) fn module(ts: TokenStream) -> TokenStream {
                 } => {
                     array_types_to_generate.push((vals.clone(), max_length));
                     (
-                        format!("__rust_array_param_{}_{}", vals, max_length),
+                        format!("__rust_array_param_{vals}_{max_length}"),
                         generated_array_ops_name(vals, max_length),
                     )
                 }

samples/rust/hostprogs/a.rs

@@ -3,5 +3,5 @@
 //! Rust single host program sample: module `a`.
 
 pub(crate) fn f(x: i32) {
-    println!("The number is {}.", x);
+    println!("The number is {x}.");
 }

scripts/generate_rust_target.rs

@@ -30,14 +30,14 @@ type Object = Vec<(String, Value)>;
 impl Display for Value {
     fn fmt(&self, formatter: &mut Formatter<'_>) -> Result {
         match self {
-            Value::Boolean(boolean) => write!(formatter, "{}", boolean),
-            Value::Number(number) => write!(formatter, "{}", number),
-            Value::String(string) => write!(formatter, "\"{}\"", string),
+            Value::Boolean(boolean) => write!(formatter, "{boolean}"),
+            Value::Number(number) => write!(formatter, "{number}"),
+            Value::String(string) => write!(formatter, "\"{string}\""),
             Value::Object(object) => {
                 formatter.write_str("{")?;
                 if let [ref rest @ .., ref last] = object[..] {
                     for (key, value) in rest {
-                        write!(formatter, "\"{}\": {},", key, value)?;
+                        write!(formatter, "\"{key}\": {value},")?;
                     }
                     write!(formatter, "\"{}\": {}", last.0, last.1)?;
                 }
@@ -95,7 +95,7 @@ impl Display for TargetSpec {
         formatter.write_str("{\n")?;
         if let [ref rest @ .., ref last] = self.0[..] {
             for (key, value) in rest {
-                write!(formatter, "    \"{}\": {},\n", key, value)?;
+                write!(formatter, "    \"{key}\": {value},\n")?;
             }
             write!(formatter, "    \"{}\": {}\n", last.0, last.1)?;
         }
@@ -228,5 +228,5 @@ fn main() {
         ts.push("target-endian", "big");
     }
 
-    println!("{}", ts);
+    println!("{ts}");
 }