Mutex::borrow only gives an immutable reference?
#224
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The reason it is done this way is because the user knows best which cell type to use (eg. |
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You can nest two Basically |
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Related: #208 |
224: Allow general exception / interrupt discovery in cortex-m-rt-macros r=korken89 a=mciantyre We propose changes to the `cortex-m-rt-macros` crate that should help us use the macros independent of the `cortex-m-rt` runtime. The changes in this PR should be backwards compatible for all `cortex-m-rt` users, while expanding the utility of the macros beyond the cortex-m-rt repository. In the [Teensy 4 libraries](https://github.com/mciantyre/teensy4-rs) we're developing, we've opted to create our own runtime crate, `teensy4-rt`. We require more support than what's available in `cortex-m-rt` to boot and take advantage of NXP iMXRT106x variants. Specifically, we have a unique start-up process, and a custom memory layout with tightly-couple memory (TCM) regions. As discussed in #164, the `cortex-m-rt` crate does not support custom memory layouts. To address the limitations and provide a faster proof-of-concept, we forked the `cortex-m-rt` crate, focusing on the runtime needs of our specific system. Despite the fork, we strive for compatibility with the `cortex-m-rt` crate. Our eventual goal is to drop the `teensy4-rt` crate, and rely on a future version of the `cortex-m-rt` crate that supports our use-case. Compatibility means supporting the macros; just as the `cortex-m-rt` crate exports the macros, the `teensy4-rt` crate exports the same macros. By requiring that the macros maintain `extern crate cortex_m_rt` declarations, we assume that the `cortex_m_rt` crate is available. However, we don't believe this is a necessary requirement. To take advantage of the `#[interrupt]` and `#[exception]` macros, a set of crates need to export two identifiers: `interrupt`, an enumeration of valid interrupt handlers; and `exception`, an enumeration of exceptions for the Cortex M variant. We have a precedent for this pattern, in that crates generated by `svd2rust` export the enumeration of valid interrupt handlers (provided the correct features are enabled) for discovery by the `#[interrupt]` macros. The PR proposes a similar strategy: export the `Exceptions` enumeration as `exception` (lower case) from the `cortex-m-rt` crate, so that exception variant discovery occurs the same as it does for interrupts. After the rename, and with the removal of `extern crate cortex_m_rt` in the two macros, it doesn't matter where the `exception` or `interrupt` enums are defined. The changes let us define a similar `exception` enumeration in our `teensy4-rt` crate, which may be picked up by the `#[exception]` macro. We've shown this to be a successful strategy in the Teensy 4 Rust libraries, which are based on our fork of the macros crate. We realize that the macros are a feature of the `cortex-m-rt` crate, not a library that others should directly depend on. Ideally, we rally around the `cortex-m-rt` crate, and keep the macros coupled to that implementation. But until we reach that point, having the macros defined without expectations of the `cortex-m-rt` crate lets us bring up new embedded targets faster while maintaining compatibility with the existing ecosystem. Co-authored-by: Ian McIntyre <[email protected]>
It seems like the
cortex_m::interrupt::Mutextype only gives an immutable reference? What's the point of the mutex then? How can I get a mutable reference to the value?The text was updated successfully, but these errors were encountered: