Alexandre Courbot
2025-Nov-02 03:00 UTC
[PATCH v6 4/5] rust: Move register and bitfield macros out of Nova
On Sun Nov 2, 2025 at 3:51 AM JST, Dirk Behme wrote:> On 09.10.25 13:28, Alexandre Courbot wrote: >> On Thu Oct 9, 2025 at 8:16 PM JST, Danilo Krummrich wrote: >>> On Thu Oct 9, 2025 at 8:59 AM CEST, Dirk Behme wrote: >>>> Assuming that register.rs is supposed to become the "generic" way to >>>> access hardware registers I started to have a look to it. Some weeks >>>> back testing interrupts I used some quite simple timer with 4 registers >>>> [1]. Now, thinking about converting it to register!() I have three >>>> understanding / usage questions: >>>> >>>> * At the moment register!() is for 32-bit registers, only? So it can't >>>> be used for my example having 8-bit and 16-bit registers as well? >>> >>> Yes, currently the register!() macro always generates a 32-bit register type >>> (mainly because nova-core did not need anything else). However, this will of >>> course be generalized (which should be pretty straight forward). >>> >>> Having a brief look at the TMU datasheet it looks like you should be able to >>> treat TSTR and TCR as 32-bit registers without any issues for testing the >>> register!() macro today. I.e. you can just define it as: >>> >>> register!(TSTR @ 0x04, "Timer Start Register" { >>> 2:2 str2 as bool, "Specifies whether TCNT2 is operated or stopped."; >>> 1:1 str1 as bool, "Specifies whether TCNT1 is operated or stopped."; >>> 0:0 str0 as bool, "Specifies whether TCNT0 is operated or stopped."; >>> }); >>> >>> Same for TCR. >> >> Patch 2 of this series actually adds support for 16 and 8 bit register >> storage. > > Hmm, how to use that with the register!() macro? I mean patch 2 adds > support for different storage widths for *bitfields*. But looking at > patch 4 [2] it looks like *register!()* still uses $name(u32)? With > that it looks like that the register!() macro still just supports 32 > bit registers? Or what have I missed? > > What I'm looking for is a way to specify if a register is 8, 16 or 32 > bit. Using the example from above something like > > register!(TSTR<u8> @ ....Errr indeed, you are correct. The `register` macro's syntax has not been updated to take advantage of `bitfield`'s storage types, and `u32` is still hardcoded as of this series. This looks like an oversight - a register is basically a bitfield with some I/O, so making it support storage types should be trivial. I guess this hasn't been done yet because Nova is the only user so far, and we don't need/want to explicitly specify a type for each register since they are invariably `u32`. But it wouldn't look good to change the syntax of `register` after moving it out, so I agree this should take place before the move. The same applies to the visiblity feature. One way to avoid a update all the declarations so far would be to give Nova its own `register` macro that invokes the one in `kernel` with the relevant parameters hardcoded.