Extend SPI capabilities

Add setting if block transfer allows different sizes of rx/tx buffers.

Author: mprse

hal/mbed_compat.c

@@ -55,6 +55,7 @@ MBED_WEAK void spi_get_capabilities(PinName ssel, bool slave, spi_capabilities_t
         cap->hw_cs_handle = false;                  // irrelevant in slave mode
         cap->slave_delay_between_symbols_ns = 2500; // 2.5 us
         cap->clk_modes = 0x0f;                      // all clock modes
+        cap->tx_rx_buffers_equal_length = true;     // rx buffer size must be equal tx buffer size
 #if DEVICE_SPI_ASYNCH
         cap->async_mode = true;
 #else
@@ -68,6 +69,7 @@ MBED_WEAK void spi_get_capabilities(PinName ssel, bool slave, spi_capabilities_t
         cap->hw_cs_handle = false;                // to be determined later based on ssel
         cap->slave_delay_between_symbols_ns = 0;  // irrelevant in master mode
         cap->clk_modes = 0x0f;                    // all clock modes
+        cap->tx_rx_buffers_equal_length = true;   // rx buffer size must be equal tx buffer size
 #if DEVICE_SPI_ASYNCH
         cap->async_mode = true;
 #else

hal/spi_api.h

@@ -84,7 +84,7 @@ typedef struct {
     bool        support_slave_mode; /**< If true, the device can handle SPI slave mode using hardware management on the specified ssel pin. */
     bool        hw_cs_handle; /**< If true, in SPI master mode Chip Select can be handled by hardware. */
     bool        async_mode; /**< If true, in async mode is supported. */
-
+    bool        tx_rx_buffers_equal_length; /**< If true, rx and tx buffers must have the same length. */
 } spi_capabilities_t;
 
 #ifdef __cplusplus
@@ -96,11 +96,11 @@ extern "C" {
  *
  * # Defined behavior
  * * ::spi_init initializes the spi_t control structure
- * * ::spi_init configures the pins used by SPI
+ * * ::spi_init configures the pins used by SPI - Verified by ::fpga_spi_test_init_free, ::fpga_spi_test_common_no_ss and ::fpga_spi_test_common
  * * ::spi_get_capabilities() fills the given `spi_capabilities_t` instance
  * * ::spi_get_capabilities() should consider the `ssel` pin when evaluation the `support_slave_mode` and `hw_cs_handle` capability
  * * ::spi_get_capabilities(): if the given `ssel` pin cannot be managed by hardware, `support_slave_mode` and `hw_cs_handle` should be false
- * * At least a symbol width of 8bit must be supported
+ * * At least a symbol width of 8bit must be supported - Verified by ::fpga_spi_test_common_no_ss and ::fpga_spi_test_common
  * * The supported frequency range must include the range [0.2..2] MHz
  * * ::spi_free returns the pins owned by the SPI object to their reset state
  * * ::spi_format sets the number of bits per frame