rust-embedded / rust-embedded/linux-embedded-hal

2 Writes give "Operation not supported on transport endpoint"

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Rust
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Description

I was trying to get the examples in https://github.com/alexeden/adafruit-seesaw to work on linux but i kept getting errors

I managed to track down the problem to this MVP example

use embedded_hal::i2c::{Error, I2c, Operation};
use linux_embedded_hal::{Delay, I2CError, I2cdev, i2cdev::core::I2CDevice};

fn main() {
    let mut i2c = I2cdev::new("/dev/i2c-10").unwrap();

    let regester_num: &[u8] = &[0x00, 0x7F];
    let mut data = [0xFF];
    let mut ops = [Operation::Write(regester_num), Operation::Write(&data)];
    i2c.transaction(0x36_u8, &mut ops).unwrap();
}
thread 'main' panicked at crates/rig/src/bin/gps.rs:10:40:
called `Result::unwrap()` on an `Err` value: I2CError { err: Errno(95) }
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

using https://www.adafruit.com/product/4471 and https://www.adafruit.com/product/5880 but i had the same issue with other i2c peripherals.

95 	EOPNOTSUPP 	Operation not supported on transport endpoint

Please note that a single write of a longer array does not cause the same error.

It should be noted that a single write operation with a longer array does run, let mut ops = [Operation::Write(&[0x00, 0x7F, 0xFF ])]

I cant tell if im doing something wrong or if there is a bug some were.

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the reproduction in crates/rig/src/bin/gps.rs and compare the two-write transaction with the single longer write using the listed Linux I2C devices. Check how I2cdev maps multiple Operation::Write values and verify the behavior against the EOPNOTSUPP result; the issue is done when the supported behavior is established and the implementation or documentation reflects it.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
embedded-iot
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
38/100

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