Alexandre Courbot
2025-Sep-09 02:37 UTC
[PATCH v2 1/4] nova-core: bitstruct: Move bitfield-specific code from register! into new macro
On Tue Sep 9, 2025 at 2:16 AM JST, Joel Fernandes wrote:> Hi Alex, > > On 9/7/2025 11:12 PM, Alexandre Courbot wrote: >> On Thu Sep 4, 2025 at 6:54 AM JST, Joel Fernandes wrote: >>> 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 at 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 { >> >> The `struct` naming here looks a bit confusing to me - as of this patch, >> this is a u32, right? And eventually these types will be limited to primitive types, >> so why not just `ControlReg: u32 {` ? > > This is done in a later patch. This patch is only code movement, in later patch > we add precisely the syntax you're describing when we add storage types, and > update the register! macro. In this patch bitstruct is only u32.My point was, is the `struct` keyword needed at all? Isn't it a bit confusing since these types are technically not Rust structs? I agree the `: u32` can be introduced later, the original `register!` macro did not specify any type information so there is indeed no reason to add it in this patch.> >> >>> +/// 3:0 mode as u8 ?=> Mode; >>> +/// 7:4 state as u8 => State; >>> +/// } >>> +/// } >>> +/// ``` >> >> As this will move to the kernel crate, it is particularly important to >> make sure that this example can compile and run - so please provide >> simple definitions for `Mode` and `State` to make sure the kunit tests >> will pass after patch 4 (in the current state I'm pretty sure they won't). > > Good catch. This will blow up the example though. I will change it to no_run > like the register! macro did if that's Ok.If you reduce `State` to 1 bit and change its type to `bool`, and limit `Mode` to two or three variants, the example should remain short. I think it is valuable to provide a complete working example here as the syntax is not obvious at first sight.