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Merge pull request #3844 from showier-drastic/main

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SpiDevice cancel safety: always set CS pin to high on drop
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Dario Nieuwenhuis 2025-02-07 13:54:14 +01:00 committed by GitHub
commit f2a6014cd3
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2 changed files with 20 additions and 0 deletions
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1
embassy-embedded-hal/Cargo.toml
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@ -22,6 +22,7 @@ time = ["dep:embassy-time"]
default = ["time"]
[dependencies]
embassy-hal-internal = { version = "0.2.0", path = "../embassy-hal-internal" }
embassy-futures = { version = "0.1.0", path = "../embassy-futures" }
embassy-sync = { version = "0.6.2", path = "../embassy-sync" }
embassy-time = { version = "0.4.0", path = "../embassy-time", optional = true }

19
embassy-embedded-hal/src/shared_bus/asynch/spi.rs
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@ -25,6 +25,7 @@
//! let display2 = ST7735::new(spi_dev2, dc2, rst2, Default::default(), 160, 128);
//! ```
use embassy_hal_internal::drop::OnDrop;
use embassy_sync::blocking_mutex::raw::RawMutex;
use embassy_sync::mutex::Mutex;
use embedded_hal_1::digital::OutputPin;
@ -70,6 +71,14 @@ where
let mut bus = self.bus.lock().await;
self.cs.set_low().map_err(SpiDeviceError::Cs)?;
let cs_drop = OnDrop::new(|| {
// This drop guard deasserts CS pin if the async operation is cancelled.
// Errors are ignored in this drop handler, as there's nothing we can do about them.
// If the async operation is completed without cancellation, this handler will not
// be run, and the CS pin will be deasserted with proper error handling.
let _ = self.cs.set_high();
});
let op_res = 'ops: {
for op in operations {
let res = match op {
@ -97,6 +106,10 @@ where
// On failure, it's important to still flush and deassert CS.
let flush_res = bus.flush().await;
// Now that all the async operations are done, we defuse the CS guard,
// and manually set the CS pin low (to better handle the possible errors).
cs_drop.defuse();
let cs_res = self.cs.set_high();
let op_res = op_res.map_err(SpiDeviceError::Spi)?;
@ -155,6 +168,11 @@ where
bus.set_config(&self.config).map_err(|_| SpiDeviceError::Config)?;
self.cs.set_low().map_err(SpiDeviceError::Cs)?;
let cs_drop = OnDrop::new(|| {
// Please see comment in SpiDevice for an explanation of this drop handler.
let _ = self.cs.set_high();
});
let op_res = 'ops: {
for op in operations {
let res = match op {
@ -182,6 +200,7 @@ where
// On failure, it's important to still flush and deassert CS.
let flush_res = bus.flush().await;
cs_drop.defuse();
let cs_res = self.cs.set_high();
let op_res = op_res.map_err(SpiDeviceError::Spi)?;