From 811cead9c66bae6eb1a1a05cd7ca7850a1be6a7e Mon Sep 17 00:00:00 2001
From: Robin Mueller <robin.mueller.m@gmail.com>
Date: Mon, 12 May 2025 10:43:33 +0200
Subject: [PATCH] update for SPI `transfer` impl

---
 CHANGELOG.md    |  4 ++++
 src/gpio/mod.rs |  2 +-
 src/spi/mod.rs  | 19 +++++++++++++------
 3 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 445eb9d..7a6067a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [unreleased]
 
+### Changed
+
+- SPI `transfer` implemenation update to handle size missmatch between read and write.
+
 ## [v0.1.0]
 
 Init commit.
diff --git a/src/gpio/mod.rs b/src/gpio/mod.rs
index 54ae665..3a3c051 100644
--- a/src/gpio/mod.rs
+++ b/src/gpio/mod.rs
@@ -1,7 +1,7 @@
 //! GPIO support module.
 use core::convert::Infallible;
 
-pub use crate::ioconfig::{regs::FunSel, FilterClkSel, FilterType};
+pub use crate::ioconfig::{FilterClkSel, FilterType, regs::FunSel};
 pub use embedded_hal::digital::PinState;
 pub use ll::{InterruptEdge, InterruptLevel, PinId, Port, Pull};
 
diff --git a/src/spi/mod.rs b/src/spi/mod.rs
index e9fcf12..16dc12b 100644
--- a/src/spi/mod.rs
+++ b/src/spi/mod.rs
@@ -860,21 +860,28 @@ where
         self.transfer_preparation(write)?;
         let mut current_read_idx = 0;
         let mut current_write_idx = self.initial_send_fifo_pumping_with_words(write);
+        let max_idx = core::cmp::max(read.len(), write.len());
         while current_read_idx < read.len() || current_write_idx < write.len() {
-            if current_write_idx < write.len() {
+            if current_write_idx < max_idx {
                 if current_write_idx == write.len() - 1 && self.bmstall {
                     nb::block!(
                         self.write_fifo(write[current_write_idx].into() | BMSTART_BMSTOP_MASK)
                     )?;
-                } else {
+                } else if current_write_idx < write.len() {
                     nb::block!(self.write_fifo(write[current_write_idx].into()))?;
+                } else {
+                    nb::block!(self.write_fifo(0))?;
                 }
                 current_write_idx += 1;
             }
-            if current_read_idx < read.len() {
-                read[current_read_idx] = (nb::block!(self.read_fifo())? & Word::MASK)
-                    .try_into()
-                    .unwrap();
+            if current_read_idx < max_idx {
+                if current_read_idx < read.len() {
+                    read[current_read_idx] = (nb::block!(self.read_fifo())? & Word::MASK)
+                        .try_into()
+                        .unwrap();
+                } else {
+                    nb::block!(self.read_fifo()).unwrap();
+                }
                 current_read_idx += 1;
             }
         }
-- 
2.43.0