extmod/machine_spi: Simplify SPI xfer function to only take one buf len.

There is no need to take src_len and dest_len arguments.  The case of
reading-only with a single output byte (originally src_len=1, dest_len>1)
is now handled by using the output buffer as the input buffer, and using
memset to fill the output byte into this buffer.  This simplifies the
implementations of the spi_transfer protocol function.

1 files changed, 1 insertions, 1 deletions

diff --git a/extmod/machine_spi.h b/extmod/machine_spi.h
index 26d716fc1..35a911d91 100644
--- a/extmod/machine_spi.h
+++ b/extmod/machine_spi.h
@@ -31,7 +31,7 @@
 
 // SPI protocol
 typedef struct _mp_machine_spi_p_t {
-    void (*transfer)(mp_obj_base_t *obj, size_t slen, const uint8_t *src, size_t dlen, uint8_t *dest);
+    void (*transfer)(mp_obj_base_t *obj, size_t len, const uint8_t *src, uint8_t *dest);
 } mp_machine_spi_p_t;
 
 MP_DECLARE_CONST_FUN_OBJ(mp_machine_spi_read_obj);