Support debug prints on `R`

[korken89]

Hi,

For example when I read a register it would be really nice in development to be able to add debug prints of the register. Eg, lets say I have a register with 2 flags:

implement_registers!(
    MyChip.registers<u8> = {
        status(RO, 0, 1) = {
            flag1: u8 as Bit = RO 0..=0,
            flag2: u8 as Bit = RO 1..=1,
        },
        // ...
    }
}

Debug-printing with {:?} I'd expect something like status::R { flag1: Set, flag2: Cleared }, and with {:#?}

status::R { 
    flag1: Set, 
    flag2: Cleared 
}

It would also be preferable if one use custom enums that there are also debug printed with correct variants.

[diondokter]

Right, this is actually more elaborate than I thought because I'd just print the buffer in hex format. But this is clearly better! So we can do both :)

How should we deal with field types that don't implement Debug themselves? Ideally we'd detect that and print the raw numbers, but I don't think we can... Or maybe we should require all fields to implement Debug? But that'd be kinda strict and not always necessary...

[korken89]

Maybe have a flag to request debug that puts a requirement on Debug and else just print it in HEX? Then the user can choose to do it or not :)

[diondokter]

So I imagine we'll like more of these extensions and restrictions the user can opt in to. Could try to emulate (only syntactically) what derive does and maybe call it generate.

implement_registers!(
    MyChip.registers<u8> = {
        #[generate(Debug)]         // <- New!
        status(RO, 0, 1) = {
            flag1: u8 as Bit = RO 0..=0,
            flag2: u8 as Bit = RO 1..=1,
        },
        // ...
    }
}

I try to avoid completely alien syntax in the macro and I think this would feel familiar and also distinct enough.

[korken89]

Looks good to me!

[diondokter]

@korken89 I added support for it! Would you mind trying it out before I merge it?