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.

2 files changed, 15 insertions, 32 deletions

diff --git a/esp8266/modpybhspi.c b/esp8266/modpybhspi.c
index c1cd7f662d..10a090269f 100644
--- a/esp8266/modpybhspi.c
+++ b/esp8266/modpybhspi.c
@@ -50,23 +50,23 @@ typedef struct _pyb_hspi_obj_t {
 } pyb_hspi_obj_t;
 
 
-STATIC void hspi_transfer(mp_obj_base_t *self_in, size_t src_len, const uint8_t *src_buf, size_t dest_len, uint8_t *dest_buf) {
+STATIC void hspi_transfer(mp_obj_base_t *self_in, size_t len, const uint8_t *src, uint8_t *dest) {
     (void)self_in;
 
-    if (dest_len == 0) {
+    if (dest == NULL) {
         // fast case when we only need to write data
         size_t chunk_size = 1024;
-        size_t count = src_len / chunk_size;
+        size_t count = len / chunk_size;
         size_t i = 0;
         for (size_t j = 0; j < count; ++j) {
             for (size_t k = 0; k < chunk_size; ++k) {
-                spi_tx8fast(HSPI, src_buf[i]);
+                spi_tx8fast(HSPI, src[i]);
                 ++i;
             }
             ets_loop_iter();
         }
-        while (i < src_len) {
-            spi_tx8fast(HSPI, src_buf[i]);
+        while (i < len) {
+            spi_tx8fast(HSPI, src[i]);
             ++i;
         }
     } else {
@@ -74,29 +74,17 @@ STATIC void hspi_transfer(mp_obj_base_t *self_in, size_t src_len, const uint8_t
 
         // Process data in chunks, let the pending tasks run in between
         size_t chunk_size = 1024; // TODO this should depend on baudrate
-        size_t count = dest_len / chunk_size;
+        size_t count = len / chunk_size;
         size_t i = 0;
         for (size_t j = 0; j < count; ++j) {
             for (size_t k = 0; k < chunk_size; ++k) {
-                uint32_t data_out;
-                if (src_len == 1) {
-                    data_out = src_buf[0];
-                } else {
-                    data_out = src_buf[i];
-                }
-                dest_buf[i] = spi_transaction(HSPI, 0, 0, 0, 0, 8, data_out, 8, 0);
+                dest[i] = spi_transaction(HSPI, 0, 0, 0, 0, 8, src[i], 8, 0);
                 ++i;
             }
             ets_loop_iter();
         }
-        while (i < dest_len) {
-            uint32_t data_out;
-            if (src_len == 1) {
-                data_out = src_buf[0];
-            } else {
-                data_out = src_buf[i];
-            }
-            dest_buf[i] = spi_transaction(HSPI, 0, 0, 0, 0, 8, data_out, 8, 0);
+        while (i < len) {
+            dest[i] = spi_transaction(HSPI, 0, 0, 0, 0, 8, src[i], 8, 0);
             ++i;
         }
     }
diff --git a/esp8266/modpybspi.c b/esp8266/modpybspi.c
index 4c4b843c5d..b9650954f3 100644
--- a/esp8266/modpybspi.c
+++ b/esp8266/modpybspi.c
@@ -47,17 +47,12 @@ typedef struct _pyb_spi_obj_t {
     mp_hal_pin_obj_t miso;
 } pyb_spi_obj_t;
 
-STATIC void mp_hal_spi_transfer(mp_obj_base_t *self_in, size_t src_len, const uint8_t *src_buf, size_t dest_len, uint8_t *dest_buf) {
+STATIC void mp_hal_spi_transfer(mp_obj_base_t *self_in, size_t len, const uint8_t *src, uint8_t *dest) {
     pyb_spi_obj_t *self = (pyb_spi_obj_t*)self_in;
     // only MSB transfer is implemented
     uint32_t delay_half = 500000 / self->baudrate + 1;
-    for (size_t i = 0; i < src_len || i < dest_len; ++i) {
-        uint8_t data_out;
-        if (src_len == 1) {
-            data_out = src_buf[0];
-        } else {
-            data_out = src_buf[i];
-        }
+    for (size_t i = 0; i < len; ++i) {
+        uint8_t data_out = src[i];
         uint8_t data_in = 0;
         for (int j = 0; j < 8; ++j, data_out <<= 1) {
             mp_hal_pin_write(self->mosi, (data_out >> 7) & 1);
@@ -77,8 +72,8 @@ STATIC void mp_hal_spi_transfer(mp_obj_base_t *self_in, size_t src_len, const ui
                 ets_delay_us(delay_half);
             }
         }
-        if (dest_len != 0) {
-            dest_buf[i] = data_in;
+        if (dest != NULL) {
+            dest[i] = data_in;
         }
         // make sure pending tasks have a chance to run
         ets_loop_iter();