spi_slave: add a flag SPI_SLAVE_NO_RETURN_RESULT to bypass return descriptor from ISR

if using this flag, driver willn't return the trans-done descriptor from ISR, so
`spi_slave_get_trans_result()` shouldn't be called.
besides, callback is the only way to know transaction status in that case, so a
`post_trans_cb` will be checked mandatory.

components/driver/include/driver/spi_master.h

@@ -224,6 +224,7 @@ esp_err_t spi_device_queue_trans(spi_device_handle_t handle, spi_transaction_t *
                         out.
  * @return
  *         - ESP_ERR_INVALID_ARG   if parameter is invalid
+ *         - ESP_ERR_NOT_SUPPORTED if flag `SPI_DEVICE_NO_RETURN_RESULT` is set
  *         - ESP_ERR_TIMEOUT       if there was no completed transaction before ticks_to_wait expired
  *         - ESP_OK                on success
  */

components/driver/include/driver/spi_slave.h

@@ -23,7 +23,7 @@ extern "C"
 #define SPI_SLAVE_TXBIT_LSBFIRST          (1<<0)  ///< Transmit command/address/data LSB first instead of the default MSB first
 #define SPI_SLAVE_RXBIT_LSBFIRST          (1<<1)  ///< Receive data LSB first instead of the default MSB first
 #define SPI_SLAVE_BIT_LSBFIRST            (SPI_SLAVE_TXBIT_LSBFIRST|SPI_SLAVE_RXBIT_LSBFIRST) ///< Transmit and receive LSB first
-
+#define SPI_SLAVE_NO_RETURN_RESULT        (1<<2)  ///< Don't return the descriptor to the host on completion (use `post_trans_cb` to notify instead)
 
 typedef struct spi_slave_transaction_t spi_slave_transaction_t;
 typedef void(*slave_transaction_cb_t)(spi_slave_transaction_t *trans);
@@ -158,6 +158,7 @@ esp_err_t spi_slave_queue_trans(spi_host_device_t host, const spi_slave_transact
  *                      out.
  * @return
  *         - ESP_ERR_INVALID_ARG   if parameter is invalid
+ *         - ESP_ERR_NOT_SUPPORTED if flag `SPI_SLAVE_NO_RETURN_RESULT` is set
  *         - ESP_OK                on success
  */
 esp_err_t spi_slave_get_trans_result(spi_host_device_t host, spi_slave_transaction_t **trans_desc, TickType_t ticks_to_wait);

components/driver/spi_master.c

@@ -381,10 +381,16 @@ esp_err_t spi_bus_add_device(spi_host_device_t host_id, const spi_device_interfa
 
     //Allocate queues, set defaults
     dev->trans_queue = xQueueCreate(dev_config->queue_size, sizeof(spi_trans_priv_t));
-    dev->ret_queue = xQueueCreate(dev_config->queue_size, sizeof(spi_trans_priv_t));
-    if (!dev->trans_queue || !dev->ret_queue) {
+    if (!dev->trans_queue) {
         goto nomem;
     }
+    //ret_queue nolonger needed if use flag SPI_DEVICE_NO_RETURN_RESULT
+    if (!(dev_config->flags & SPI_DEVICE_NO_RETURN_RESULT)) {
+        dev->ret_queue = xQueueCreate(dev_config->queue_size, sizeof(spi_trans_priv_t));
+        if (!dev->ret_queue) {
+            goto nomem;
+        }
+    }
 
     //We want to save a copy of the dev config in the dev struct.
     memcpy(&dev->cfg, dev_config, sizeof(spi_device_interface_config_t));
@@ -445,15 +451,17 @@ esp_err_t spi_bus_remove_device(spi_device_handle_t handle)
     //catch design errors and aren't meant to be triggered during normal operation.
     SPI_CHECK(uxQueueMessagesWaiting(handle->trans_queue)==0, "Have unfinished transactions", ESP_ERR_INVALID_STATE);
     SPI_CHECK(handle->host->cur_cs == DEV_NUM_MAX || handle->host->device[handle->host->cur_cs] != handle, "Have unfinished transactions", ESP_ERR_INVALID_STATE);
-    SPI_CHECK(uxQueueMessagesWaiting(handle->ret_queue)==0, "Have unfinished transactions", ESP_ERR_INVALID_STATE);
+    if (handle->ret_queue) {
+        SPI_CHECK(uxQueueMessagesWaiting(handle->ret_queue)==0, "Have unfinished transactions", ESP_ERR_INVALID_STATE);
+    }
 
     //return
     int spics_io_num = handle->cfg.spics_io_num;
     if (spics_io_num >= 0) spicommon_cs_free_io(spics_io_num);
 
     //Kill queues
-    vQueueDelete(handle->trans_queue);
-    vQueueDelete(handle->ret_queue);
+    if (handle->trans_queue) vQueueDelete(handle->trans_queue);
+    if (handle->ret_queue) vQueueDelete(handle->ret_queue);
     spi_bus_lock_unregister_dev(handle->dev_lock);
 
     assert(handle->host->device[handle->id] == handle);
@@ -852,6 +860,9 @@ esp_err_t SPI_MASTER_ATTR spi_device_get_trans_result(spi_device_handle_t handle
     spi_trans_priv_t trans_buf;
     SPI_CHECK(handle!=NULL, "invalid dev handle", ESP_ERR_INVALID_ARG);
 
+    //if SPI_DEVICE_NO_RETURN_RESULT is set, ret_queue will always be empty
+    SPI_CHECK(!(handle->cfg.flags & SPI_DEVICE_NO_RETURN_RESULT), "API not Supported!", ESP_ERR_NOT_SUPPORTED);
+
     //use the interrupt, block until return
     r=xQueueReceive(handle->ret_queue, (void*)&trans_buf, ticks_to_wait);
     if (!r) {

components/driver/spi_slave.c

@@ -125,6 +125,11 @@ esp_err_t spi_slave_initialize(spi_host_device_t host, const spi_bus_config_t *b
 #endif
     SPI_CHECK(slave_config->spics_io_num < 0 || GPIO_IS_VALID_GPIO(slave_config->spics_io_num), "spics pin invalid", ESP_ERR_INVALID_ARG);
 
+    //Check post_trans_cb status when `SPI_SLAVE_NO_RETURN_RESULT` flag is set.
+    if(slave_config->flags & SPI_SLAVE_NO_RETURN_RESULT) {
+        SPI_CHECK(slave_config->post_trans_cb != NULL, "use feature flag 'SPI_SLAVE_NO_RETURN_RESULT' but no post_trans_cb function sets", ESP_ERR_INVALID_ARG);
+    }
+
     spi_chan_claimed=spicommon_periph_claim(host, "spi slave");
     SPI_CHECK(spi_chan_claimed, "host already in use", ESP_ERR_INVALID_STATE);
 
@@ -183,11 +188,17 @@ esp_err_t spi_slave_initialize(spi_host_device_t host, const spi_bus_config_t *b
 
     //Create queues
     spihost[host]->trans_queue = xQueueCreate(slave_config->queue_size, sizeof(spi_slave_transaction_t *));
-    spihost[host]->ret_queue = xQueueCreate(slave_config->queue_size, sizeof(spi_slave_transaction_t *));
-    if (!spihost[host]->trans_queue || !spihost[host]->ret_queue) {
+    if (!spihost[host]->trans_queue) {
         ret = ESP_ERR_NO_MEM;
         goto cleanup;
     }
+    if(!(slave_config->flags & SPI_SLAVE_NO_RETURN_RESULT)) {
+        spihost[host]->ret_queue = xQueueCreate(slave_config->queue_size, sizeof(spi_slave_transaction_t *));
+        if (!spihost[host]->ret_queue) {
+            ret = ESP_ERR_NO_MEM;
+            goto cleanup;
+        }
+    }
 
     int flags = bus_config->intr_flags | ESP_INTR_FLAG_INTRDISABLED;
     err = esp_intr_alloc(spicommon_irqsource_for_host(host), flags, spi_intr, (void *)spihost[host], &spihost[host]->intr);
@@ -298,6 +309,9 @@ esp_err_t SPI_SLAVE_ATTR spi_slave_get_trans_result(spi_host_device_t host, spi_
     BaseType_t r;
     SPI_CHECK(is_valid_host(host), "invalid host", ESP_ERR_INVALID_ARG);
     SPI_CHECK(spihost[host], "host not slave", ESP_ERR_INVALID_ARG);
+    //if SPI_SLAVE_NO_RETURN_RESULT is set, ret_queue will always be empty
+    SPI_CHECK(!(spihost[host]->cfg.flags & SPI_SLAVE_NO_RETURN_RESULT), "API not Supported!", ESP_ERR_NOT_SUPPORTED);
+
     r = xQueueReceive(spihost[host]->ret_queue, (void *)trans_desc, ticks_to_wait);
     if (!r) return ESP_ERR_TIMEOUT;
     return ESP_OK;
@@ -349,9 +363,10 @@ static void SPI_SLAVE_ISR_ATTR spi_intr(void *arg)
             spicommon_dmaworkaround_req_reset(host->tx_dma_chan, spi_slave_restart_after_dmareset, host);
         }
         if (host->cfg.post_trans_cb) host->cfg.post_trans_cb(host->cur_trans);
-        //Okay, transaction is done.
-        //Return transaction descriptor.
-        xQueueSendFromISR(host->ret_queue, &host->cur_trans, &do_yield);
+
+        if(!(host->cfg.flags & SPI_SLAVE_NO_RETURN_RESULT)) {
+            xQueueSendFromISR(host->ret_queue, &host->cur_trans, &do_yield);
+        }
         host->cur_trans = NULL;
     }
     if (use_dma) {