Provide a simple helper function to check whether given flags do
contain one or multiple other flags.

This is used by a subsequent patch implementing the Cmalloc `Allocator`
to check for __GFP_ZERO.

Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 rust/kernel/alloc.rs | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/rust/kernel/alloc.rs b/rust/kernel/alloc.rs
index 8a1cecc20d09..615afe69d097 100644
--- a/rust/kernel/alloc.rs
+++ b/rust/kernel/alloc.rs
@@ -34,7 +34,7 @@
 /// They can be combined with the operators `|`, `&`, and `!`.
 ///
 /// Values can be used from the [`flags`] module.
-#[derive(Clone, Copy)]
+#[derive(Clone, Copy, PartialEq)]
 pub struct Flags(u32);
 
 impl Flags {
@@ -42,6 +42,11 @@ impl Flags {
     pub(crate) fn as_raw(self) -> u32 {
         self.0
     }
+
+    /// Check whether `flags` is contained in `self`.
+    pub fn contains(&self, flags: Flags) -> bool {
+        (*self & flags) == flags
+    }
 }
 
 impl core::ops::BitOr for Flags {
-- 
2.45.2

On Mon, Aug 5, 2024 at 5:22 PM Danilo Krummrich <dakr@kernel.org> wrote:
>
> Provide a simple helper function to check whether given flags do
> contain one or multiple other flags.
>
> This is used by a subsequent patch implementing the Cmalloc `Allocator`
> to check for __GFP_ZERO.
>
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>

One nit, but:

Reviewed-by: Alice Ryhl <aliceryhl@google.com>

>  rust/kernel/alloc.rs | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/rust/kernel/alloc.rs b/rust/kernel/alloc.rs
> index 8a1cecc20d09..615afe69d097 100644
> --- a/rust/kernel/alloc.rs
> +++ b/rust/kernel/alloc.rs
> @@ -34,7 +34,7 @@
>  /// They can be combined with the operators `|`, `&`, and `!`.
>  ///
>  /// Values can be used from the [`flags`] module.
> -#[derive(Clone, Copy)]
> +#[derive(Clone, Copy, PartialEq)]
>  pub struct Flags(u32);
>
>  impl Flags {
> @@ -42,6 +42,11 @@ impl Flags {
>      pub(crate) fn as_raw(self) -> u32 {
>          self.0
>      }
> +
> +    /// Check whether `flags` is contained in `self`.
> +    pub fn contains(&self, flags: Flags) -> bool {
> +        (*self & flags) == flags
> +    }

Since this type is Copy, you can do this:

pub fn contains(self, flags: Flags) -> bool {
    (self & flags) == flags
}

and avoid the asterisk.

Alice