spi_master: add check for trans len

The driver decide whether use MOSI/MISO phases according to the buffer
address together with the SPI_TRANS_USE_*DATA. However someone may assue
that these phases will be skipped when the ``length``/``rxlength`` is
set to 0. In fact it is a feature that ``rxlength`` is allowed to be
set to 0 when tx and rx have the same length, and the driver fill the
``rxlength`` to ``length``.

An error check is added when the rxlength is 0 but there is data to be
sent.

components/driver/spi_master.c

@@ -1103,6 +1103,14 @@ static SPI_MASTER_ISR_ATTR esp_err_t check_trans_valid(spi_device_handle_t handl
     SPI_CHECK(!((trans_desc->flags & (SPI_TRANS_MODE_DIO|SPI_TRANS_MODE_QIO)) && (!(handle->cfg.flags & SPI_DEVICE_HALFDUPLEX))), "incompatible iface params", ESP_ERR_INVALID_ARG);
     SPI_CHECK( !(handle->cfg.flags & SPI_DEVICE_HALFDUPLEX) || host->dma_chan == 0 || !(trans_desc->flags & SPI_TRANS_USE_RXDATA || trans_desc->rx_buffer != NULL)
         || !(trans_desc->flags & SPI_TRANS_USE_TXDATA || trans_desc->tx_buffer!=NULL), "SPI half duplex mode does not support using DMA with both MOSI and MISO phases.", ESP_ERR_INVALID_ARG );
+    //MOSI phase is skipped only when both tx_buffer and SPI_TRANS_USE_TXDATA are not set.
+    SPI_CHECK(trans_desc->length != 0 || (trans_desc->tx_buffer == NULL && !(trans_desc->flags & SPI_TRANS_USE_TXDATA)),
+        "trans tx_buffer should be NULL and SPI_TRANS_USE_TXDATA should be cleared to skip MOSI phase.", ESP_ERR_INVALID_ARG);
+    //MISO phase is skipped only when both rx_buffer and SPI_TRANS_USE_RXDATA are not set.
+    //If set rxlength=0 in full_duplex mode, it will be automatically set to length
+    SPI_CHECK(!(handle->cfg.flags & SPI_DEVICE_HALFDUPLEX) || trans_desc->rxlength != 0 ||
+        (trans_desc->rx_buffer == NULL && ((trans_desc->flags & SPI_TRANS_USE_RXDATA)==0)),
+        "trans rx_buffer should be NULL and SPI_TRANS_USE_RXDATA should be cleared to skip MISO phase.", ESP_ERR_INVALID_ARG);
     //In Full duplex mode, default rxlength to be the same as length, if not filled in.
     // set rxlength to length is ok, even when rx buffer=NULL
     if (trans_desc->rxlength==0 && !(handle->cfg.flags & SPI_DEVICE_HALFDUPLEX)) {