First pass at implementing derivedFrom.

[nsabovic]

Trying to fix #181, this is the first pass at implementing derivedFrom. These also the very first lines I've ever written in Rust, so be gentle.

This patch requires rust-embedded/svd#49.

With this patch, I get a bit further in generating the peripherals for SAM D10.

[jamesmunns]

Hey @nsabovic, sorry there hasn't been any response yet. I'll try to review and test this over the next few days, and also follow rust-embedded/svd#49 to see if anything happens there.

Thanks for contributing!

[wez]

This seems to do the job, except for the (totally forgivable) rust newbie mistake with the semicolons I mentioned inline.

With that fixed, its generating code like this for me with the atsamd21 svd:

impl Deref for SERCOM4 {
    type Target = sercom0::RegisterBlock;
    fn deref(&self) -> &sercom0::RegisterBlock {
        unsafe { &*SERCOM4::ptr() }
    }
}

[wez]

Need to remove the ; from the end of the line here and in the else branch below because they're causing base to have the type () rather than the Ident type that you're constructing here, and that causes things to explode because the generated code comes out like this:

impl Deref for SERCOM4 {
    type Target = ( ) :: RegisterBlock ;
...
``

[wez]

@nsabovic are you planning to do something similar for registers?

[wez]

FWIW, I'd vote for inlining the helper from rust-embedded/svd#49 into this PR and it will be easier to land and integrate just a single PR; PR dependencies are a PITA :)

fn derive_peripheral(p: &Peripheral, other: &Peripheral) -> Peripheral {
    let mut derived = p.clone();
    if derived.group_name.is_none() && other.group_name.is_some() {
        derived.group_name = other.group_name.clone();
    }
    if derived.description.is_none() && other.description.is_some() {
        derived.description = other.description.clone();
    }
    if derived.registers.is_none() && other.registers.is_some() {
        derived.registers = other.registers.clone();
    }
    if derived.interrupt.is_empty() {
        derived.interrupt = other.interrupt.clone();
    }
    derived
}

[wez]

Over in rust-embedded/svd#50 I've added parsing out the <register derivedFrom= attribute, and together with this PR, I have some code on top that expands derived registers: https://github.com/wez/svd2rust/tree/derivedFrom.

That resolves the bad sizing issue that @kevinmehall mentioned in #181 (comment). Actually, I think all three of those points have now been addressed and we just need to review, clean things up and land them.

[nsabovic]

@wez thanks for catching that 👍

Registers, clusters and fields can all derive from others, would be nice to make a more general solution. My chip's SVD (SAM D10) doesn't have <register derivedFrom=""> in the SVD, so I spaced out on that part of the spec completely...

...but it does have alternateCluster and alternateRegister, so I'd love to have those—the API with unions, does it require using unsafe all over the place? I was thinking, since my chip has an alternate register for, say PER register in dither5 mode, to have in the impl of PER register a function called as_dither5(), which would give you a dither5 view of the same register, while also taking a reference so you can't access it in both modes at the same time. Seems rustier, and also capitalizes on the fact that there is a default register, and the alternate register. What do you think?

[mathk]

Ping from triage: This need to be review. Also merge/rebase is needed.

[Disasm]

Ping from triage: @nsabovic could you rebase your changes?

[ryankurte]

bors try

[bors]

try

Build failed

• continuous-integration/travis-ci/push

[ryankurte]

looks like a few things need to be fixed after rebase (sorry @nsabovic!)

@@ -76,10 +76,10 @@ pub fn render(
     }
 
     // erc: *E*ither *R*egister or *C*luster
-    let ercs = p.registers.as_ref().map(|x| x.as_ref()).unwrap_or(&[][..]);
+    let ercs: Vec<Either<Register, Cluster>> = p.registers.as_ref().map(|x| x.as_ref()).unwrap_or(&[][..]);
 
     let registers: &[&Register] = &util::only_registers(&ercs)[..];
-    let clusters = util::only_clusters(ercs);
+    let clusters = util::only_clusters(&ercs);
 
     // No `struct RegisterBlock` can be generated
     if registers.is_empty() && clusters.is_empty() {
@@ -90,7 +90,7 @@ pub fn render(
 
     // Push any register or cluster blocks into the output
     let mut mod_items = vec![];
-    mod_items.push(register_or_cluster_block(ercs, defaults, None, nightly)?);
+    mod_items.push(register_or_cluster_block(&ercs, defaults, None, nightly)?);
 
     // Push all cluster related information into the peripheral module
     for c in &clusters {

[ryankurte]

where does the Peripheral::derive_from(&mut self, p: Peripheral) method come from? (this might have got disappeared during rebase..?)

[michalfita]

Does anyone has working branch with stuff for supporting derivedFrom? I tried @wez's and @nsabovic's and both fail to build.

[therealprof]

@nsabovic Sorry for the long delay. Are you still interested in working on this? If so would you mind bringing the PR into a working state?

[wez]

#256 is the successor to this PR

[nsabovic]

I am not really set up to look at this right now. If you need it urgently, I'm not the best bet.

[adamgreig]

Closing in preference of now merged #319 which is built on this and #256.