stm32: Add support for a board to reserve certain peripherals.

Allows reserving CAN, I2C, SPI, Timer and UART peripherals.  If reserved
the peripheral cannot be accessed from Python.

Signed-off-by: Damien George <damien@micropython.org>

ports/stm32/i2c.c

@@ -534,6 +534,12 @@ int i2c_find_peripheral(mp_obj_t id) {
             mp_raise_msg_varg(&mp_type_ValueError, MP_ERROR_TEXT("I2C(%d) doesn't exist"), i2c_id);
         }
     }
+
+    // check if the I2C is reserved for system use or not
+    if (MICROPY_HW_I2C_IS_RESERVED(i2c_id)) {
+        mp_raise_msg_varg(&mp_type_ValueError, MP_ERROR_TEXT("I2C(%d) is reserved"), i2c_id);
+    }
+
     return i2c_id;
 }
 

ports/stm32/machine_uart.c

@@ -345,6 +345,11 @@ STATIC mp_obj_t pyb_uart_make_new(const mp_obj_type_t *type, size_t n_args, size
         }
     }
 
+    // check if the UART is reserved for system use or not
+    if (MICROPY_HW_UART_IS_RESERVED(uart_id)) {
+        mp_raise_msg_varg(&mp_type_ValueError, MP_ERROR_TEXT("UART(%d) is reserved"), uart_id);
+    }
+
     pyb_uart_obj_t *self;
     if (MP_STATE_PORT(pyb_uart_obj_all)[uart_id - 1] == NULL) {
         // create new UART object

ports/stm32/mpconfigboard_common.h

@@ -127,6 +127,31 @@
 #define MICROPY_HW_FLASH_FS_LABEL "pybflash"
 #endif
 
+// Function to determine if the given can_id is reserved for system use or not.
+#ifndef MICROPY_HW_CAN_IS_RESERVED
+#define MICROPY_HW_CAN_IS_RESERVED(can_id) (false)
+#endif
+
+// Function to determine if the given i2c_id is reserved for system use or not.
+#ifndef MICROPY_HW_I2C_IS_RESERVED
+#define MICROPY_HW_I2C_IS_RESERVED(i2c_id) (false)
+#endif
+
+// Function to determine if the given spi_id is reserved for system use or not.
+#ifndef MICROPY_HW_SPI_IS_RESERVED
+#define MICROPY_HW_SPI_IS_RESERVED(spi_id) (false)
+#endif
+
+// Function to determine if the given tim_id is reserved for system use or not.
+#ifndef MICROPY_HW_TIM_IS_RESERVED
+#define MICROPY_HW_TIM_IS_RESERVED(tim_id) (false)
+#endif
+
+// Function to determine if the given uart_id is reserved for system use or not.
+#ifndef MICROPY_HW_UART_IS_RESERVED
+#define MICROPY_HW_UART_IS_RESERVED(uart_id) (false)
+#endif
+
 /*****************************************************************************/
 // General configuration
 

ports/stm32/pyb_can.c

@@ -203,6 +203,11 @@ STATIC mp_obj_t pyb_can_make_new(const mp_obj_type_t *type, size_t n_args, size_
         mp_raise_msg_varg(&mp_type_ValueError, MP_ERROR_TEXT("CAN(%d) doesn't exist"), can_idx);
     }
 
+    // check if the CAN is reserved for system use or not
+    if (MICROPY_HW_CAN_IS_RESERVED(can_idx)) {
+        mp_raise_msg_varg(&mp_type_ValueError, MP_ERROR_TEXT("CAN(%d) is reserved"), can_idx);
+    }
+
     pyb_can_obj_t *self;
     if (MP_STATE_PORT(pyb_can_obj_all)[can_idx - 1] == NULL) {
         self = m_new_obj(pyb_can_obj_t);

ports/stm32/spi.c

@@ -167,45 +167,52 @@ void spi_init0(void) {
 }
 
 int spi_find_index(mp_obj_t id) {
+    int spi_id;
     if (mp_obj_is_str(id)) {
         // given a string id
         const char *port = mp_obj_str_get_str(id);
         if (0) {
         #ifdef MICROPY_HW_SPI1_NAME
         } else if (strcmp(port, MICROPY_HW_SPI1_NAME) == 0) {
-            return 1;
+            spi_id = 1;
         #endif
         #ifdef MICROPY_HW_SPI2_NAME
         } else if (strcmp(port, MICROPY_HW_SPI2_NAME) == 0) {
-            return 2;
+            spi_id = 2;
         #endif
         #ifdef MICROPY_HW_SPI3_NAME
         } else if (strcmp(port, MICROPY_HW_SPI3_NAME) == 0) {
-            return 3;
+            spi_id = 3;
         #endif
         #ifdef MICROPY_HW_SPI4_NAME
         } else if (strcmp(port, MICROPY_HW_SPI4_NAME) == 0) {
-            return 4;
+            spi_id = 4;
         #endif
         #ifdef MICROPY_HW_SPI5_NAME
         } else if (strcmp(port, MICROPY_HW_SPI5_NAME) == 0) {
-            return 5;
+            spi_id = 5;
         #endif
         #ifdef MICROPY_HW_SPI6_NAME
         } else if (strcmp(port, MICROPY_HW_SPI6_NAME) == 0) {
-            return 6;
+            spi_id = 6;
         #endif
+        } else {
+            mp_raise_msg_varg(&mp_type_ValueError, MP_ERROR_TEXT("SPI(%s) doesn't exist"), port);
         }
-        mp_raise_msg_varg(&mp_type_ValueError, MP_ERROR_TEXT("SPI(%s) doesn't exist"), port);
     } else {
         // given an integer id
-        int spi_id = mp_obj_get_int(id);
-        if (spi_id >= 1 && spi_id <= MP_ARRAY_SIZE(spi_obj)
-            && spi_obj[spi_id - 1].spi != NULL) {
-            return spi_id;
+        spi_id = mp_obj_get_int(id);
+        if (spi_id < 1 || spi_id > MP_ARRAY_SIZE(spi_obj) || spi_obj[spi_id - 1].spi == NULL) {
+            mp_raise_msg_varg(&mp_type_ValueError, MP_ERROR_TEXT("SPI(%d) doesn't exist"), spi_id);
         }
-        mp_raise_msg_varg(&mp_type_ValueError, MP_ERROR_TEXT("SPI(%d) doesn't exist"), spi_id);
     }
+
+    // check if the SPI is reserved for system use or not
+    if (MICROPY_HW_SPI_IS_RESERVED(spi_id)) {
+        mp_raise_msg_varg(&mp_type_ValueError, MP_ERROR_TEXT("SPI(%d) is reserved"), spi_id);
+    }
+
+    return spi_id;
 }
 
 STATIC uint32_t spi_get_source_freq(SPI_HandleTypeDef *spi) {

ports/stm32/timer.c

@@ -896,6 +896,11 @@ STATIC mp_obj_t pyb_timer_make_new(const mp_obj_type_t *type, size_t n_args, siz
         mp_raise_msg_varg(&mp_type_ValueError, MP_ERROR_TEXT("Timer(%d) doesn't exist"), tim_id);
     }
 
+    // check if the timer is reserved for system use or not
+    if (MICROPY_HW_TIM_IS_RESERVED(tim_id)) {
+        mp_raise_msg_varg(&mp_type_ValueError, MP_ERROR_TEXT("Timer(%d) is reserved"), tim_id);
+    }
+
     pyb_timer_obj_t *tim;
     if (MP_STATE_PORT(pyb_timer_obj_all)[tim_id - 1] == NULL) {
         // create new Timer object