I2c: simplify, expand docs, document shared bus usage.#440
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Alright, let's get this merged.
Thank you for your work!
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445: bus/i2c: add RefCell, CriticalSection and Mutex shared bus implementations. r=eldruin a=Dirbaio Requires #440 Same as #443 but for I2C. This adds a few bus sharing implementations, with varying tradeoffs: - `RefCellDevice`: single thread only - `CriticalSectionDevice`: thread-safe, coarse locking, nostd. - `MutexDevice`: thread-safe, fine-grained locking, std only. Co-authored-by: Dario Nieuwenhuis <dirbaio@dirbaio.net>
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Matches changes made in rust-embedded/embedded-hal#440
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Matches changes made in rust-embedded/embedded-hal#440
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Depends on #441 -- check that one out first.This does some simplifications to the trait that I think we should do:
transaction. This way HALs have to implement just that.write_iterandwrite_iter_read. The reason is that they're quite inefficient, especially with DMA implementations. We've already removed these on other traits, so I think we should do as well here.transaction_iter. I don't think it's much useful in practice, because the way iterators work all the yieldedOperations must have the same lifetime. This means that, even if the user can generate theOperations on the fly, they can't allocate buffers for these on the fly, all buffers must be pre-allocated. So it's not useful for, say, streaming a large transfer by reusing some small buffer repeatedly. See I2C transaction_iter should take an iterator of mutable references #367readandwrite, I think they're clearer.It also specifies how i2c bus sharing is supposed to work. This is an alternative to #392 . After the discussions there, I don't think we should split I2C into Bus and Device anymore. For SPI it makes sense, because drivers want to enforce that there's a CS pin (
SpiDevice) or not (SpiBus). This is not the case with I2C, the API is exactly the same in the shared and non-shared case. Drivers shouldn't care which case it is.So all we have to do to "support" bus sharing is docs, This PR does: