From bffa5be2f49fdd5e223df8dae7df88f52bde83e8 Mon Sep 17 00:00:00 2001
From: Dario Nieuwenhuis <dirbaio@dirbaio.net>
Date: Thu, 15 Dec 2022 19:43:36 +0100
Subject: [PATCH] nrf/uart: do not error on zero length transfers.

It's a perfectly fine thing to do, should be just a noop. Erroring is
really annoying when you're writing a payload to uart that might
be zero-length or not.
---
 embassy-nrf/src/uarte.rs | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/embassy-nrf/src/uarte.rs b/embassy-nrf/src/uarte.rs
index 63df1b68..4703c1a5 100644
--- a/embassy-nrf/src/uarte.rs
+++ b/embassy-nrf/src/uarte.rs
@@ -53,7 +53,6 @@ impl Default for Config {
 #[non_exhaustive]
 pub enum Error {
     BufferTooLong,
-    BufferZeroLength,
     DMABufferNotInDataMemory,
     // TODO: add other error variants.
 }
@@ -370,10 +369,11 @@ impl<'d, T: Instance> UarteTx<'d, T> {
     }
 
     pub async fn write_from_ram(&mut self, buffer: &[u8]) -> Result<(), Error> {
-        slice_in_ram_or(buffer, Error::DMABufferNotInDataMemory)?;
         if buffer.len() == 0 {
-            return Err(Error::BufferZeroLength);
+            return Ok(());
         }
+
+        slice_in_ram_or(buffer, Error::DMABufferNotInDataMemory)?;
         if buffer.len() > EASY_DMA_SIZE {
             return Err(Error::BufferTooLong);
         }
@@ -437,10 +437,11 @@ impl<'d, T: Instance> UarteTx<'d, T> {
     }
 
     pub fn blocking_write_from_ram(&mut self, buffer: &[u8]) -> Result<(), Error> {
-        slice_in_ram_or(buffer, Error::DMABufferNotInDataMemory)?;
         if buffer.len() == 0 {
-            return Err(Error::BufferZeroLength);
+            return Ok(());
         }
+
+        slice_in_ram_or(buffer, Error::DMABufferNotInDataMemory)?;
         if buffer.len() > EASY_DMA_SIZE {
             return Err(Error::BufferTooLong);
         }
@@ -550,7 +551,7 @@ impl<'d, T: Instance> UarteRx<'d, T> {
 
     pub async fn read(&mut self, buffer: &mut [u8]) -> Result<(), Error> {
         if buffer.len() == 0 {
-            return Err(Error::BufferZeroLength);
+            return Ok(());
         }
         if buffer.len() > EASY_DMA_SIZE {
             return Err(Error::BufferTooLong);
@@ -603,7 +604,7 @@ impl<'d, T: Instance> UarteRx<'d, T> {
 
     pub fn blocking_read(&mut self, buffer: &mut [u8]) -> Result<(), Error> {
         if buffer.len() == 0 {
-            return Err(Error::BufferZeroLength);
+            return Ok(());
         }
         if buffer.len() > EASY_DMA_SIZE {
             return Err(Error::BufferTooLong);
@@ -672,7 +673,7 @@ impl<'d, T: Instance, U: TimerInstance> UarteRxWithIdle<'d, T, U> {
 
     pub async fn read_until_idle(&mut self, buffer: &mut [u8]) -> Result<usize, Error> {
         if buffer.len() == 0 {
-            return Err(Error::BufferZeroLength);
+            return Ok(0);
         }
         if buffer.len() > EASY_DMA_SIZE {
             return Err(Error::BufferTooLong);
@@ -728,7 +729,7 @@ impl<'d, T: Instance, U: TimerInstance> UarteRxWithIdle<'d, T, U> {
 
     pub fn blocking_read_until_idle(&mut self, buffer: &mut [u8]) -> Result<usize, Error> {
         if buffer.len() == 0 {
-            return Err(Error::BufferZeroLength);
+            return Ok(0);
         }
         if buffer.len() > EASY_DMA_SIZE {
             return Err(Error::BufferTooLong);
@@ -918,7 +919,6 @@ mod eh1 {
         fn kind(&self) -> embedded_hal_1::serial::ErrorKind {
             match *self {
                 Self::BufferTooLong => embedded_hal_1::serial::ErrorKind::Other,
-                Self::BufferZeroLength => embedded_hal_1::serial::ErrorKind::Other,
                 Self::DMABufferNotInDataMemory => embedded_hal_1::serial::ErrorKind::Other,
             }
         }