Add spi_get_capabilities() function to HAL API

Add also default weak version of spi_get_capabilities() which provides default/most common SPI parameters.
This function can be replaced if a specific target has different capabilities.

hal/mbed_compat.c

@@ -17,6 +17,7 @@
 
 #include "analogin_api.h"
 #include "i2c_api.h"
+#include "spi_api.h"
 #include "gpio_api.h"
 #include "mbed_toolchain.h"
 
@@ -40,4 +41,53 @@ MBED_WEAK void analogin_free(analogin_t *obj)
 {
     // Do nothing
 }
+#endif
+
+#if DEVICE_SPI
+// Default SPI capabilities. If specific target has different capabilities this function needs to be re-implemented.
+MBED_WEAK void spi_get_capabilities(PinName ssel, bool slave, spi_capabilities_t *cap)
+{
+    if (slave) {
+        cap->minimum_frequency = 200000;            // 200 kHz
+        cap->maximum_frequency = 2000000;           // 2 MHz
+        cap->word_length = 0x00008080;              // 8 and 16 bit symbols
+        cap->support_slave_mode = false;            // to be determined later based on ssel
+        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
+#if DEVICE_SPI_ASYNCH
+        cap->async_mode = true;
+#else
+        cap->async_mode = false;
+#endif
+    } else {
+        cap->minimum_frequency = 200000;          // 200 kHz
+        cap->maximum_frequency = 2000000;         // 2 MHz
+        cap->word_length = 0x00008080;            // 8 and 16 bit symbols
+        cap->support_slave_mode = false;          // to be determined later based on ssel
+        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
+#if DEVICE_SPI_ASYNCH
+        cap->async_mode = true;
+#else
+        cap->async_mode = false;
+#endif
+    }
+
+    // check if given ssel pin is in the cs pinmap
+    const PinMap *cs_pins = spi_master_cs_pinmap();
+    PinName pin = NC;
+    while (cs_pins->pin != NC) {
+        if (cs_pins->pin == ssel) {
+#if DEVICE_SPISLAVE
+            cap->support_slave_mode = true;
+#endif
+            cap->hw_cs_handle = true;
+            break;
+        }
+        cs_pins++;
+    }
+}
+
 #endif

hal/spi_api.h

@@ -53,6 +53,28 @@ typedef struct spi_s spi_t;
 
 #endif
 
+/**
+ * Describes the capabilities of a SPI peripherals
+ */
+typedef struct {
+    /** Minimum frequency supported must be set by target device and it will be assessed during
+     *  testing.
+     */
+    uint32_t    minimum_frequency;
+    /** Maximum frequency supported must be set by target device and it will be assessed during
+     *  testing.
+     */
+    uint32_t    maximum_frequency;
+    /** Each bit represents the corresponding word length. lsb => 1bit, msb => 32bit. */
+    uint32_t    word_length;
+    uint16_t    slave_delay_between_symbols_ns; /**< specifies required number of ns between transmission of successive symbols in slave mode. */
+    uint8_t     clk_modes; /**< specifies supported modes from spi_mode_t. Each bit represents the corresponding mode. */
+    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. */
+
+} spi_capabilities_t;
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -63,6 +85,11 @@ extern "C" {
  * # Defined behavior
  * * ::spi_init initializes the spi_t control structure
  * * ::spi_init configures the pins used by SPI
+ * * ::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
+ * * 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
  * * ::spi_format configures clock polarity and phase
@@ -125,6 +152,11 @@ extern "C" {
 SPIName spi_get_peripheral_name(PinName mosi, PinName miso, PinName mclk);
 #endif
 
+/**
+ * Fills the given spi_capabilities_t structure with the capabilities of the given peripheral.
+ */
+void spi_get_capabilities(PinName ssel, bool slave, spi_capabilities_t *cap);
+
 /** Initialize the SPI peripheral
  *
  * Configures the pins used by SPI, sets a default format and frequency, and enables the peripheral