SpiDevice's interface can't be used for streaming transactions

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#583 8 comments 4 reactions 0 assignees View on GitHub

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
25/100
Issue type
Feature
Clarity
Needs clarification
Activity status
Stale
Tech stack
rust
Domain
embedded-iot

Research direction

Start by reading the stabilized SpiDevice interface and the Operation type mentioned in the issue. Compare the existing transaction model with iterator- or closure-based approaches, focusing on avoiding the per-operation slice overhead for streaming writes. Done would be a settled API direction that supports one transaction without requiring that allocation, with its compatibility and validation requirements established.

Written by the indexing model from the issue text.

Description

There are applications where, when writing data to an SPI device, it is more efficient to write the data in a single transaction rather than multiple transactions (my use case is an SPI screen that can write multiple lines in a single transaction).

However, with the current SpiDevice interface, I would need to create a slice of Operations in order to be able to write all the lines in a single transaction. Because I need a new Operation for each separate line, this requires 128 lines * 8 bytes per slice = 1KiB of additional data just for the pointers (the framebuffer itself is only 2 KiB!). The chip I am targeting only has 40KiB of memory total, so this is a substantial amount of overhead.

The interface is now stabilized because the crate is at 1.0, but is there some change that can be made to improve this situation? (e.g. an interface that takes an iterator of Operations, a closure-based interface, or something similar)

Dominant language
Rust
Stars
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Forks
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PR merge metrics
No merged PRs in 30d

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