[PATCH v2 1/4] nova-core: bitstruct: Move bitfield-specific code from register! into new macro

[Joel Fernandes <joelagnelf@nvidia.com>]

The bitfield-specific into new macro. This will be used to define
structs with bitfields, similar to C language.

Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
---
 drivers/gpu/nova-core/bitstruct.rs   | 271 +++++++++++++++++++++++++++
 drivers/gpu/nova-core/nova_core.rs   |   3 +
 drivers/gpu/nova-core/regs/macros.rs | 247 +-----------------------
 3 files changed, 282 insertions(+), 239 deletions(-)
 create mode 100644 drivers/gpu/nova-core/bitstruct.rs

diff --git a/drivers/gpu/nova-core/bitstruct.rs b/drivers/gpu/nova-core/bitstruct.rs
new file mode 100644
index 000000000000..1dd9edab7d07
--- /dev/null
+++ b/drivers/gpu/nova-core/bitstruct.rs
@@ -0,0 +1,271 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+// bitstruct.rs — Bitfield library for Rust structures
+//
+// A library that provides support for defining bit fields in Rust
+// structures. Also used from things that need bitfields like register macro.
+///
+/// # Syntax
+///
+/// ```rust
+/// bitstruct! {
+///     struct ControlReg {
+///         3:0       mode        as u8 ?=> Mode;
+///         7:4       state       as u8 => State;
+///     }
+/// }
+/// ```
+///
+/// This generates a struct with:
+/// - Field accessors: `mode()`, `state()`, etc.
+/// - Field setters: `set_mode()`, `set_state()`, etc. (supports builder pattern).
+/// - Debug and Default implementations
+///
+/// The field setters can be used with the builder pattern, example:
+/// ControlReg::default().set_mode(mode).set_state(state);
+///
+/// Fields are defined as follows:
+///
+/// - `as <type>` simply returns the field value casted to <type>, typically `u32`, `u16`, `u8` or
+///   `bool`. Note that `bool` fields must have a range of 1 bit.
+/// - `as <type> => <into_type>` calls `<into_type>`'s `From::<<type>>` implementation and returns
+///   the result.
+/// - `as <type> ?=> <try_into_type>` calls `<try_into_type>`'s `TryFrom::<<type>>` implementation
+///   and returns the result. This is useful with fields for which not all values are valid.
+macro_rules! bitstruct {
+    // Main entry point - defines the bitfield struct with fields
+    (struct $name:ident $(, $comment:literal)? { $($fields:tt)* }) => {
+        bitstruct!(@core $name $(, $comment)? { $($fields)* });
+    };
+
+    // All rules below are helpers.
+
+    // Defines the wrapper `$name` type, as well as its relevant implementations (`Debug`,
+    // `Default`, `BitOr`, and conversion to the value type) and field accessor methods.
+    (@core $name:ident $(, $comment:literal)? { $($fields:tt)* }) => {
+        $(
+        #[doc=$comment]
+        )?
+        #[repr(transparent)]
+        #[derive(Clone, Copy)]
+        pub(crate) struct $name(u32);
+
+        impl ::core::ops::BitOr for $name {
+            type Output = Self;
+
+            fn bitor(self, rhs: Self) -> Self::Output {
+                Self(self.0 | rhs.0)
+            }
+        }
+
+        impl ::core::convert::From<$name> for u32 {
+            fn from(val: $name) -> u32 {
+                val.0
+            }
+        }
+
+        bitstruct!(@fields_dispatcher $name { $($fields)* });
+    };
+
+    // Captures the fields and passes them to all the implementers that require field information.
+    //
+    // Used to simplify the matching rules for implementers, so they don't need to match the entire
+    // complex fields rule even though they only make use of part of it.
+    (@fields_dispatcher $name:ident {
+        $($hi:tt:$lo:tt $field:ident as $type:tt
+            $(?=> $try_into_type:ty)?
+            $(=> $into_type:ty)?
+            $(, $comment:literal)?
+        ;
+        )*
+    }
+    ) => {
+        bitstruct!(@field_accessors $name {
+            $(
+                $hi:$lo $field as $type
+                $(?=> $try_into_type)?
+                $(=> $into_type)?
+                $(, $comment)?
+            ;
+            )*
+        });
+        bitstruct!(@debug $name { $($field;)* });
+        bitstruct!(@default $name { $($field;)* });
+    };
+
+    // Defines all the field getter/setter methods for `$name`.
+    (
+        @field_accessors $name:ident {
+        $($hi:tt:$lo:tt $field:ident as $type:tt
+            $(?=> $try_into_type:ty)?
+            $(=> $into_type:ty)?
+            $(, $comment:literal)?
+        ;
+        )*
+        }
+    ) => {
+        $(
+            bitstruct!(@check_field_bounds $hi:$lo $field as $type);
+        )*
+
+        #[allow(dead_code)]
+        impl $name {
+            $(
+            bitstruct!(@field_accessor $name $hi:$lo $field as $type
+                $(?=> $try_into_type)?
+                $(=> $into_type)?
+                $(, $comment)?
+                ;
+            );
+            )*
+        }
+    };
+
+    // Boolean fields must have `$hi == $lo`.
+    (@check_field_bounds $hi:tt:$lo:tt $field:ident as bool) => {
+        #[allow(clippy::eq_op)]
+        const _: () = {
+            ::kernel::build_assert!(
+                $hi == $lo,
+                concat!("boolean field `", stringify!($field), "` covers more than one bit")
+            );
+        };
+    };
+
+    // Non-boolean fields must have `$hi >= $lo`.
+    (@check_field_bounds $hi:tt:$lo:tt $field:ident as $type:tt) => {
+        #[allow(clippy::eq_op)]
+        const _: () = {
+            ::kernel::build_assert!(
+                $hi >= $lo,
+                concat!("field `", stringify!($field), "`'s MSB is smaller than its LSB")
+            );
+        };
+    };
+
+    // Catches fields defined as `bool` and convert them into a boolean value.
+    (
+        @field_accessor $name:ident $hi:tt:$lo:tt $field:ident as bool => $into_type:ty
+            $(, $comment:literal)?;
+    ) => {
+        bitstruct!(
+            @leaf_accessor $name $hi:$lo $field
+            { |f| <$into_type>::from(if f != 0 { true } else { false }) }
+            $into_type => $into_type $(, $comment)?;
+        );
+    };
+
+    // Shortcut for fields defined as `bool` without the `=>` syntax.
+    (
+        @field_accessor $name:ident $hi:tt:$lo:tt $field:ident as bool $(, $comment:literal)?;
+    ) => {
+        bitstruct!(@field_accessor $name $hi:$lo $field as bool => bool $(, $comment)?;);
+    };
+
+    // Catches the `?=>` syntax for non-boolean fields.
+    (
+        @field_accessor $name:ident $hi:tt:$lo:tt $field:ident as $type:tt ?=> $try_into_type:ty
+            $(, $comment:literal)?;
+    ) => {
+        bitstruct!(@leaf_accessor $name $hi:$lo $field
+            { |f| <$try_into_type>::try_from(f as $type) } $try_into_type =>
+            ::core::result::Result<
+                $try_into_type,
+                <$try_into_type as ::core::convert::TryFrom<$type>>::Error
+            >
+            $(, $comment)?;);
+    };
+
+    // Catches the `=>` syntax for non-boolean fields.
+    (
+        @field_accessor $name:ident $hi:tt:$lo:tt $field:ident as $type:tt => $into_type:ty
+            $(, $comment:literal)?;
+    ) => {
+        bitstruct!(@leaf_accessor $name $hi:$lo $field
+            { |f| <$into_type>::from(f as $type) } $into_type => $into_type $(, $comment)?;);
+    };
+
+    // Shortcut for non-boolean fields defined without the `=>` or `?=>` syntax.
+    (
+        @field_accessor $name:ident $hi:tt:$lo:tt $field:ident as $type:tt
+            $(, $comment:literal)?;
+    ) => {
+        bitstruct!(@field_accessor $name $hi:$lo $field as $type => $type $(, $comment)?;);
+    };
+
+    // Generates the accessor methods for a single field.
+    (
+        @leaf_accessor $name:ident $hi:tt:$lo:tt $field:ident
+            { $process:expr } $to_type:ty => $res_type:ty $(, $comment:literal)?;
+    ) => {
+        ::kernel::macros::paste!(
+        const [<$field:upper _RANGE>]: ::core::ops::RangeInclusive<u8> = $lo..=$hi;
+        const [<$field:upper _MASK>]: u32 = ((((1 << $hi) - 1) << 1) + 1) - ((1 << $lo) - 1);
+        const [<$field:upper _SHIFT>]: u32 = Self::[<$field:upper _MASK>].trailing_zeros();
+        );
+
+        $(
+        #[doc="Returns the value of this field:"]
+        #[doc=$comment]
+        )?
+        #[inline(always)]
+        pub(crate) fn $field(self) -> $res_type {
+            ::kernel::macros::paste!(
+            const MASK: u32 = $name::[<$field:upper _MASK>];
+            const SHIFT: u32 = $name::[<$field:upper _SHIFT>];
+            );
+            let field = ((self.0 & MASK) >> SHIFT);
+
+            $process(field)
+        }
+
+        ::kernel::macros::paste!(
+        $(
+        #[doc="Sets the value of this field:"]
+        #[doc=$comment]
+        )?
+        #[inline(always)]
+        pub(crate) fn [<set_ $field>](mut self, value: $to_type) -> Self {
+            const MASK: u32 = $name::[<$field:upper _MASK>];
+            const SHIFT: u32 = $name::[<$field:upper _SHIFT>];
+            let value = (u32::from(value) << SHIFT) & MASK;
+            self.0 = (self.0 & !MASK) | value;
+
+            self
+        }
+        );
+    };
+
+    // Generates the `Debug` implementation for `$name`.
+    (@debug $name:ident { $($field:ident;)* }) => {
+        impl ::core::fmt::Debug for $name {
+            fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
+                f.debug_struct(stringify!($name))
+                    .field("<raw>", &format_args!("{:#x}", &self.0))
+                $(
+                    .field(stringify!($field), &self.$field())
+                )*
+                    .finish()
+            }
+        }
+    };
+
+    // Generates the `Default` implementation for `$name`.
+    (@default $name:ident { $($field:ident;)* }) => {
+        /// Returns a value for the bitstruct where all fields are set to their default value.
+        impl ::core::default::Default for $name {
+            fn default() -> Self {
+                #[allow(unused_mut)]
+                let mut value = Self(Default::default());
+
+                ::kernel::macros::paste!(
+                $(
+                value.[<set_ $field>](Default::default());
+                )*
+                );
+
+                value
+            }
+        }
+    };
+}
diff --git a/drivers/gpu/nova-core/nova_core.rs b/drivers/gpu/nova-core/nova_core.rs
index cb2bbb30cba1..b218a2d42573 100644
--- a/drivers/gpu/nova-core/nova_core.rs
+++ b/drivers/gpu/nova-core/nova_core.rs
@@ -2,6 +2,9 @@
 
 //! Nova Core GPU Driver
 
+#[macro_use]
+mod bitstruct;
+
 mod dma;
 mod driver;
 mod falcon;
diff --git a/drivers/gpu/nova-core/regs/macros.rs b/drivers/gpu/nova-core/regs/macros.rs
index 754c14ee7f40..3fb6852dff04 100644
--- a/drivers/gpu/nova-core/regs/macros.rs
+++ b/drivers/gpu/nova-core/regs/macros.rs
@@ -284,25 +284,25 @@ pub(crate) trait RegisterBase<T> {
 macro_rules! register {
     // Creates a register at a fixed offset of the MMIO space.
     ($name:ident @ $offset:literal $(, $comment:literal)? { $($fields:tt)* } ) => {
-        register!(@core $name $(, $comment)? { $($fields)* } );
+        bitstruct!(struct $name $(, $comment)? { $($fields)* } );
         register!(@io_fixed $name @ $offset);
     };
 
     // Creates an alias register of fixed offset register `alias` with its own fields.
     ($name:ident => $alias:ident $(, $comment:literal)? { $($fields:tt)* } ) => {
-        register!(@core $name $(, $comment)? { $($fields)* } );
+        bitstruct!(struct $name $(, $comment)? { $($fields)* } );
         register!(@io_fixed $name @ $alias::OFFSET);
     };
 
     // Creates a register at a relative offset from a base address provider.
     ($name:ident @ $base:ty [ $offset:literal ] $(, $comment:literal)? { $($fields:tt)* } ) => {
-        register!(@core $name $(, $comment)? { $($fields)* } );
+        bitstruct!(struct $name $(, $comment)? { $($fields)* } );
         register!(@io_relative $name @ $base [ $offset ]);
     };
 
     // Creates an alias register of relative offset register `alias` with its own fields.
     ($name:ident => $base:ty [ $alias:ident ] $(, $comment:literal)? { $($fields:tt)* }) => {
-        register!(@core $name $(, $comment)? { $($fields)* } );
+        bitstruct!(struct $name $(, $comment)? { $($fields)* } );
         register!(@io_relative $name @ $base [ $alias::OFFSET ]);
     };
 
@@ -313,7 +313,7 @@ macro_rules! register {
         }
     ) => {
         static_assert!(::core::mem::size_of::<u32>() <= $stride);
-        register!(@core $name $(, $comment)? { $($fields)* } );
+        bitstruct!(struct $name $(, $comment)? { $($fields)* } );
         register!(@io_array $name @ $offset [ $size ; $stride ]);
     };
 
@@ -334,7 +334,7 @@ macro_rules! register {
             $(, $comment:literal)? { $($fields:tt)* }
     ) => {
         static_assert!(::core::mem::size_of::<u32>() <= $stride);
-        register!(@core $name $(, $comment)? { $($fields)* } );
+        bitstruct!(struct $name $(, $comment)? { $($fields)* } );
         register!(@io_relative_array $name @ $base [ $offset [ $size ; $stride ] ]);
     };
 
@@ -356,7 +356,7 @@ macro_rules! register {
         }
     ) => {
         static_assert!($idx < $alias::SIZE);
-        register!(@core $name $(, $comment)? { $($fields)* } );
+        bitstruct!(struct $name $(, $comment)? { $($fields)* } );
         register!(@io_relative $name @ $base [ $alias::OFFSET + $idx * $alias::STRIDE ] );
     };
 
@@ -365,241 +365,10 @@ macro_rules! register {
     // to avoid it being interpreted in place of the relative register array alias rule.
     ($name:ident => $alias:ident [ $idx:expr ] $(, $comment:literal)? { $($fields:tt)* }) => {
         static_assert!($idx < $alias::SIZE);
-        register!(@core $name $(, $comment)? { $($fields)* } );
+        bitstruct!(struct $name $(, $comment)? { $($fields)* } );
         register!(@io_fixed $name @ $alias::OFFSET + $idx * $alias::STRIDE );
     };
 
-    // All rules below are helpers.
-
-    // Defines the wrapper `$name` type, as well as its relevant implementations (`Debug`,
-    // `Default`, `BitOr`, and conversion to the value type) and field accessor methods.
-    (@core $name:ident $(, $comment:literal)? { $($fields:tt)* }) => {
-        $(
-        #[doc=$comment]
-        )?
-        #[repr(transparent)]
-        #[derive(Clone, Copy)]
-        pub(crate) struct $name(u32);
-
-        impl ::core::ops::BitOr for $name {
-            type Output = Self;
-
-            fn bitor(self, rhs: Self) -> Self::Output {
-                Self(self.0 | rhs.0)
-            }
-        }
-
-        impl ::core::convert::From<$name> for u32 {
-            fn from(reg: $name) -> u32 {
-                reg.0
-            }
-        }
-
-        register!(@fields_dispatcher $name { $($fields)* });
-    };
-
-    // Captures the fields and passes them to all the implementers that require field information.
-    //
-    // Used to simplify the matching rules for implementers, so they don't need to match the entire
-    // complex fields rule even though they only make use of part of it.
-    (@fields_dispatcher $name:ident {
-        $($hi:tt:$lo:tt $field:ident as $type:tt
-            $(?=> $try_into_type:ty)?
-            $(=> $into_type:ty)?
-            $(, $comment:literal)?
-        ;
-        )*
-    }
-    ) => {
-        register!(@field_accessors $name {
-            $(
-                $hi:$lo $field as $type
-                $(?=> $try_into_type)?
-                $(=> $into_type)?
-                $(, $comment)?
-            ;
-            )*
-        });
-        register!(@debug $name { $($field;)* });
-        register!(@default $name { $($field;)* });
-    };
-
-    // Defines all the field getter/methods methods for `$name`.
-    (
-        @field_accessors $name:ident {
-        $($hi:tt:$lo:tt $field:ident as $type:tt
-            $(?=> $try_into_type:ty)?
-            $(=> $into_type:ty)?
-            $(, $comment:literal)?
-        ;
-        )*
-        }
-    ) => {
-        $(
-            register!(@check_field_bounds $hi:$lo $field as $type);
-        )*
-
-        #[allow(dead_code)]
-        impl $name {
-            $(
-            register!(@field_accessor $name $hi:$lo $field as $type
-                $(?=> $try_into_type)?
-                $(=> $into_type)?
-                $(, $comment)?
-                ;
-            );
-            )*
-        }
-    };
-
-    // Boolean fields must have `$hi == $lo`.
-    (@check_field_bounds $hi:tt:$lo:tt $field:ident as bool) => {
-        #[allow(clippy::eq_op)]
-        const _: () = {
-            ::kernel::build_assert!(
-                $hi == $lo,
-                concat!("boolean field `", stringify!($field), "` covers more than one bit")
-            );
-        };
-    };
-
-    // Non-boolean fields must have `$hi >= $lo`.
-    (@check_field_bounds $hi:tt:$lo:tt $field:ident as $type:tt) => {
-        #[allow(clippy::eq_op)]
-        const _: () = {
-            ::kernel::build_assert!(
-                $hi >= $lo,
-                concat!("field `", stringify!($field), "`'s MSB is smaller than its LSB")
-            );
-        };
-    };
-
-    // Catches fields defined as `bool` and convert them into a boolean value.
-    (
-        @field_accessor $name:ident $hi:tt:$lo:tt $field:ident as bool => $into_type:ty
-            $(, $comment:literal)?;
-    ) => {
-        register!(
-            @leaf_accessor $name $hi:$lo $field
-            { |f| <$into_type>::from(if f != 0 { true } else { false }) }
-            $into_type => $into_type $(, $comment)?;
-        );
-    };
-
-    // Shortcut for fields defined as `bool` without the `=>` syntax.
-    (
-        @field_accessor $name:ident $hi:tt:$lo:tt $field:ident as bool $(, $comment:literal)?;
-    ) => {
-        register!(@field_accessor $name $hi:$lo $field as bool => bool $(, $comment)?;);
-    };
-
-    // Catches the `?=>` syntax for non-boolean fields.
-    (
-        @field_accessor $name:ident $hi:tt:$lo:tt $field:ident as $type:tt ?=> $try_into_type:ty
-            $(, $comment:literal)?;
-    ) => {
-        register!(@leaf_accessor $name $hi:$lo $field
-            { |f| <$try_into_type>::try_from(f as $type) } $try_into_type =>
-            ::core::result::Result<
-                $try_into_type,
-                <$try_into_type as ::core::convert::TryFrom<$type>>::Error
-            >
-            $(, $comment)?;);
-    };
-
-    // Catches the `=>` syntax for non-boolean fields.
-    (
-        @field_accessor $name:ident $hi:tt:$lo:tt $field:ident as $type:tt => $into_type:ty
-            $(, $comment:literal)?;
-    ) => {
-        register!(@leaf_accessor $name $hi:$lo $field
-            { |f| <$into_type>::from(f as $type) } $into_type => $into_type $(, $comment)?;);
-    };
-
-    // Shortcut for non-boolean fields defined without the `=>` or `?=>` syntax.
-    (
-        @field_accessor $name:ident $hi:tt:$lo:tt $field:ident as $type:tt
-            $(, $comment:literal)?;
-    ) => {
-        register!(@field_accessor $name $hi:$lo $field as $type => $type $(, $comment)?;);
-    };
-
-    // Generates the accessor methods for a single field.
-    (
-        @leaf_accessor $name:ident $hi:tt:$lo:tt $field:ident
-            { $process:expr } $to_type:ty => $res_type:ty $(, $comment:literal)?;
-    ) => {
-        ::kernel::macros::paste!(
-        const [<$field:upper _RANGE>]: ::core::ops::RangeInclusive<u8> = $lo..=$hi;
-        const [<$field:upper _MASK>]: u32 = ((((1 << $hi) - 1) << 1) + 1) - ((1 << $lo) - 1);
-        const [<$field:upper _SHIFT>]: u32 = Self::[<$field:upper _MASK>].trailing_zeros();
-        );
-
-        $(
-        #[doc="Returns the value of this field:"]
-        #[doc=$comment]
-        )?
-        #[inline(always)]
-        pub(crate) fn $field(self) -> $res_type {
-            ::kernel::macros::paste!(
-            const MASK: u32 = $name::[<$field:upper _MASK>];
-            const SHIFT: u32 = $name::[<$field:upper _SHIFT>];
-            );
-            let field = ((self.0 & MASK) >> SHIFT);
-
-            $process(field)
-        }
-
-        ::kernel::macros::paste!(
-        $(
-        #[doc="Sets the value of this field:"]
-        #[doc=$comment]
-        )?
-        #[inline(always)]
-        pub(crate) fn [<set_ $field>](mut self, value: $to_type) -> Self {
-            const MASK: u32 = $name::[<$field:upper _MASK>];
-            const SHIFT: u32 = $name::[<$field:upper _SHIFT>];
-            let value = (u32::from(value) << SHIFT) & MASK;
-            self.0 = (self.0 & !MASK) | value;
-
-            self
-        }
-        );
-    };
-
-    // Generates the `Debug` implementation for `$name`.
-    (@debug $name:ident { $($field:ident;)* }) => {
-        impl ::core::fmt::Debug for $name {
-            fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
-                f.debug_struct(stringify!($name))
-                    .field("<raw>", &format_args!("{:#x}", &self.0))
-                $(
-                    .field(stringify!($field), &self.$field())
-                )*
-                    .finish()
-            }
-        }
-    };
-
-    // Generates the `Default` implementation for `$name`.
-    (@default $name:ident { $($field:ident;)* }) => {
-        /// Returns a value for the register where all fields are set to their default value.
-        impl ::core::default::Default for $name {
-            fn default() -> Self {
-                #[allow(unused_mut)]
-                let mut value = Self(Default::default());
-
-                ::kernel::macros::paste!(
-                $(
-                value.[<set_ $field>](Default::default());
-                )*
-                );
-
-                value
-            }
-        }
-    };
-
     // Generates the IO accessors for a fixed offset register.
     (@io_fixed $name:ident @ $offset:expr) => {
         #[allow(dead_code)]
-- 
2.34.1