rust: spi: add spi_sync

Signed-off-by: Ryo Munakata <ryomnktml@gmail.com>

Author: pfpacket

rust/helpers.c

@@ -698,6 +698,18 @@ int rust_helper_spi_read(struct spi_device *spi, void *buf, size_t len)
 	return spi_read(spi, buf, len);
 }
 EXPORT_SYMBOL_GPL(rust_helper_spi_read);
+
+void rust_helper_spi_message_init(struct spi_message *m)
+{
+	spi_message_init(m);
+}
+EXPORT_SYMBOL_GPL(rust_helper_spi_message_init);
+
+void rust_helper_spi_message_add_tail(struct spi_transfer *t, struct spi_message *m)
+{
+	spi_message_add_tail(t, m);
+}
+EXPORT_SYMBOL_GPL(rust_helper_spi_message_add_tail);
 #endif
 
 /*

rust/kernel/spi.rs

@@ -326,6 +326,37 @@ impl Device {
         })
     }
 
+    /// Blocking/synchronous SPI data transfers
+    ///
+    /// This call may only be used from a context that may sleep.  The sleep
+    /// is non-interruptible, and has no timeout.  Low-overhead controller
+    /// drivers may DMA directly into and out of the message buffers.
+    ///
+    /// # Safety
+    /// `tx_buf` and `rx_buf` must be DMA-safe otherwise UB.
+    pub unsafe fn sync(&self, tx_buf: &[u8], rx_buf: &mut [u8]) -> Result {
+        let mut tx_transfer = bindings::spi_transfer {
+            tx_buf: tx_buf.as_ptr() as _,
+            len: tx_buf.len() as _,
+            ..Default::default()
+        };
+        let mut rx_transfer = bindings::spi_transfer {
+            rx_buf: rx_buf.as_mut_ptr() as _,
+            len: rx_buf.len() as _,
+            ..Default::default()
+        };
+
+        let mut message: bindings::spi_message = Default::default();
+        unsafe {
+            bindings::spi_message_init(&mut message as _);
+            bindings::spi_message_add_tail(&mut tx_transfer as _, &mut message as _);
+            bindings::spi_message_add_tail(&mut rx_transfer as _, &mut message as _);
+
+            // SAFETY: `Device` is alive until it gets dropped
+            to_result(bindings::spi_sync(self.0, &mut message as _))
+        }
+    }
+
     /// SPI synchronous write
     pub fn write(&self, tx_buf: &[u8]) -> Result {
         to_result(unsafe {