extmod/machine_i2c: Add init protocol method for generic I2C bindings.

Hardware I2C implementations must provide a .init() protocol method if they
want to support reconfiguration.  Otherwise the default is that i2c.init()
raises an OSError (currently the case for all ports).

mp_machine_soft_i2c_locals_dict is renamed to mp_machine_i2c_locals_dict to
match the generic SPI bindings.

Fixes issue #6623 (where calling .init() on a HW I2C would crash).

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

extmod/machine_i2c.c

@@ -300,45 +300,18 @@ STATIC int mp_machine_i2c_writeto(mp_obj_base_t *self, uint16_t addr, const uint
 }
 
 /******************************************************************************/
-// MicroPython bindings for I2C
+// MicroPython bindings for generic machine.I2C
 
-STATIC void mp_machine_soft_i2c_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kind_t kind) {
-    mp_machine_soft_i2c_obj_t *self = MP_OBJ_TO_PTR(self_in);
-    mp_printf(print, "SoftI2C(scl=" MP_HAL_PIN_FMT ", sda=" MP_HAL_PIN_FMT ", freq=%u)",
-        mp_hal_pin_name(self->scl), mp_hal_pin_name(self->sda), 500000 / self->us_delay);
-}
-
-STATIC void machine_i2c_obj_init_helper(machine_i2c_obj_t *self, size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
-    enum { ARG_scl, ARG_sda, ARG_freq, ARG_timeout };
-    static const mp_arg_t allowed_args[] = {
-        { MP_QSTR_scl, MP_ARG_REQUIRED | MP_ARG_OBJ, {.u_obj = MP_OBJ_NULL} },
-        { MP_QSTR_sda, MP_ARG_REQUIRED | MP_ARG_OBJ, {.u_obj = MP_OBJ_NULL} },
-        { MP_QSTR_freq, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 400000} },
-        { MP_QSTR_timeout, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 255} },
-    };
-    mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
-    mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
-    self->scl = mp_hal_get_pin_obj(args[ARG_scl].u_obj);
-    self->sda = mp_hal_get_pin_obj(args[ARG_sda].u_obj);
-    self->us_timeout = args[ARG_timeout].u_int;
-    mp_hal_i2c_init(self, args[ARG_freq].u_int);
-}
-
-STATIC mp_obj_t mp_machine_soft_i2c_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *args) {
-    // create new soft I2C object
-    machine_i2c_obj_t *self = m_new_obj(machine_i2c_obj_t);
-    self->base.type = &mp_machine_soft_i2c_type;
-    mp_map_t kw_args;
-    mp_map_init_fixed_table(&kw_args, n_kw, args + n_args);
-    machine_i2c_obj_init_helper(self, n_args, args, &kw_args);
-    return MP_OBJ_FROM_PTR(self);
-}
-
-STATIC mp_obj_t machine_i2c_obj_init(size_t n_args, const mp_obj_t *args, mp_map_t *kw_args) {
-    machine_i2c_obj_init_helper(MP_OBJ_TO_PTR(args[0]), n_args - 1, args + 1, kw_args);
+STATIC mp_obj_t machine_i2c_init(size_t n_args, const mp_obj_t *args, mp_map_t *kw_args) {
+    mp_obj_base_t *self = (mp_obj_base_t *)MP_OBJ_TO_PTR(args[0]);
+    mp_machine_i2c_p_t *i2c_p = (mp_machine_i2c_p_t *)self->type->protocol;
+    if (i2c_p->init == NULL) {
+        mp_raise_msg(&mp_type_OSError, MP_ERROR_TEXT("I2C operation not supported"));
+    }
+    i2c_p->init(self, n_args - 1, args + 1, kw_args);
     return mp_const_none;
 }
-MP_DEFINE_CONST_FUN_OBJ_KW(machine_i2c_init_obj, 1, machine_i2c_obj_init);
+MP_DEFINE_CONST_FUN_OBJ_KW(machine_i2c_init_obj, 1, machine_i2c_init);
 
 STATIC mp_obj_t machine_i2c_scan(mp_obj_t self_in) {
     mp_obj_base_t *self = MP_OBJ_TO_PTR(self_in);
@@ -653,8 +626,45 @@ STATIC const mp_rom_map_elem_t machine_i2c_locals_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_readfrom_mem_into), MP_ROM_PTR(&machine_i2c_readfrom_mem_into_obj) },
     { MP_ROM_QSTR(MP_QSTR_writeto_mem), MP_ROM_PTR(&machine_i2c_writeto_mem_obj) },
 };
+MP_DEFINE_CONST_DICT(mp_machine_i2c_locals_dict, machine_i2c_locals_dict_table);
 
-MP_DEFINE_CONST_DICT(mp_machine_soft_i2c_locals_dict, machine_i2c_locals_dict_table);
+/******************************************************************************/
+// Implementation of soft I2C
+
+STATIC void mp_machine_soft_i2c_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kind_t kind) {
+    mp_machine_soft_i2c_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    mp_printf(print, "SoftI2C(scl=" MP_HAL_PIN_FMT ", sda=" MP_HAL_PIN_FMT ", freq=%u)",
+        mp_hal_pin_name(self->scl), mp_hal_pin_name(self->sda), 500000 / self->us_delay);
+}
+
+STATIC void mp_machine_soft_i2c_init(mp_obj_base_t *self_in, size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
+    enum { ARG_scl, ARG_sda, ARG_freq, ARG_timeout };
+    static const mp_arg_t allowed_args[] = {
+        { MP_QSTR_scl, MP_ARG_REQUIRED | MP_ARG_OBJ, {.u_obj = MP_OBJ_NULL} },
+        { MP_QSTR_sda, MP_ARG_REQUIRED | MP_ARG_OBJ, {.u_obj = MP_OBJ_NULL} },
+        { MP_QSTR_freq, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 400000} },
+        { MP_QSTR_timeout, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 255} },
+    };
+
+    mp_machine_soft_i2c_obj_t *self = (mp_machine_soft_i2c_obj_t *)self_in;
+    mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
+    mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
+
+    self->scl = mp_hal_get_pin_obj(args[ARG_scl].u_obj);
+    self->sda = mp_hal_get_pin_obj(args[ARG_sda].u_obj);
+    self->us_timeout = args[ARG_timeout].u_int;
+    mp_hal_i2c_init(self, args[ARG_freq].u_int);
+}
+
+STATIC mp_obj_t mp_machine_soft_i2c_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *args) {
+    // create new soft I2C object
+    machine_i2c_obj_t *self = m_new_obj(machine_i2c_obj_t);
+    self->base.type = &mp_machine_soft_i2c_type;
+    mp_map_t kw_args;
+    mp_map_init_fixed_table(&kw_args, n_kw, args + n_args);
+    mp_machine_soft_i2c_init(&self->base, n_args, args, &kw_args);
+    return MP_OBJ_FROM_PTR(self);
+}
 
 int mp_machine_soft_i2c_read(mp_obj_base_t *self_in, uint8_t *dest, size_t len, bool nack) {
     machine_i2c_obj_t *self = (machine_i2c_obj_t *)self_in;
@@ -684,6 +694,7 @@ int mp_machine_soft_i2c_write(mp_obj_base_t *self_in, const uint8_t *src, size_t
 }
 
 STATIC const mp_machine_i2c_p_t mp_machine_soft_i2c_p = {
+    .init = mp_machine_soft_i2c_init,
     .start = (int (*)(mp_obj_base_t *))mp_hal_i2c_start,
     .stop = (int (*)(mp_obj_base_t *))mp_hal_i2c_stop,
     .read = mp_machine_soft_i2c_read,
@@ -697,7 +708,7 @@ const mp_obj_type_t mp_machine_soft_i2c_type = {
     .print = mp_machine_soft_i2c_print,
     .make_new = mp_machine_soft_i2c_make_new,
     .protocol = &mp_machine_soft_i2c_p,
-    .locals_dict = (mp_obj_dict_t *)&mp_machine_soft_i2c_locals_dict,
+    .locals_dict = (mp_obj_dict_t *)&mp_machine_i2c_locals_dict,
 };
 
 #endif // MICROPY_PY_MACHINE_I2C

extmod/machine_i2c.h

@@ -51,9 +51,12 @@ typedef struct _mp_machine_i2c_buf_t {
 } mp_machine_i2c_buf_t;
 
 // I2C protocol
-// the first 4 methods can be NULL, meaning operation is not supported
-// transfer_single only needs to be set if transfer=mp_machine_i2c_transfer_adaptor
+// - init must be non-NULL
+// - start/stop/read/write can be NULL, meaning operation is not supported
+// - transfer must be non-NULL
+// - transfer_single only needs to be set if transfer=mp_machine_i2c_transfer_adaptor
 typedef struct _mp_machine_i2c_p_t {
+    void (*init)(mp_obj_base_t *obj, size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args);
     int (*start)(mp_obj_base_t *obj);
     int (*stop)(mp_obj_base_t *obj);
     int (*read)(mp_obj_base_t *obj, uint8_t *dest, size_t len, bool nack);
@@ -71,7 +74,7 @@ typedef struct _mp_machine_soft_i2c_obj_t {
 } mp_machine_soft_i2c_obj_t;
 
 extern const mp_obj_type_t mp_machine_soft_i2c_type;
-extern const mp_obj_dict_t mp_machine_soft_i2c_locals_dict;
+extern const mp_obj_dict_t mp_machine_i2c_locals_dict;
 
 int mp_machine_i2c_transfer_adaptor(mp_obj_base_t *self, uint16_t addr, size_t n, mp_machine_i2c_buf_t *bufs, unsigned int flags);
 int mp_machine_soft_i2c_transfer(mp_obj_base_t *self, uint16_t addr, size_t n, mp_machine_i2c_buf_t *bufs, unsigned int flags);

ports/esp32/machine_i2c.c

@@ -177,5 +177,5 @@ const mp_obj_type_t machine_hw_i2c_type = {
     .print = machine_hw_i2c_print,
     .make_new = machine_hw_i2c_make_new,
     .protocol = &machine_hw_i2c_p,
-    .locals_dict = (mp_obj_dict_t *)&mp_machine_soft_i2c_locals_dict,
+    .locals_dict = (mp_obj_dict_t *)&mp_machine_i2c_locals_dict,
 };

ports/nrf/modules/machine/i2c.c

@@ -167,7 +167,7 @@ const mp_obj_type_t machine_hard_i2c_type = {
     .print = machine_hard_i2c_print,
     .make_new = machine_hard_i2c_make_new,
     .protocol = &machine_hard_i2c_p,
-    .locals_dict = (mp_obj_dict_t*)&mp_machine_soft_i2c_locals_dict,
+    .locals_dict = (mp_obj_dict_t*)&mp_machine_i2c_locals_dict,
 };
 
 #endif // MICROPY_PY_MACHINE_I2C

ports/stm32/machine_i2c.c

@@ -273,7 +273,7 @@ const mp_obj_type_t machine_hard_i2c_type = {
     .print = machine_hard_i2c_print,
     .make_new = machine_hard_i2c_make_new,
     .protocol = &machine_hard_i2c_p,
-    .locals_dict = (mp_obj_dict_t *)&mp_machine_soft_i2c_locals_dict,
+    .locals_dict = (mp_obj_dict_t *)&mp_machine_i2c_locals_dict,
 };
 
 #endif // MICROPY_HW_ENABLE_HW_I2C

ports/zephyr/machine_i2c.c

@@ -134,5 +134,5 @@ const mp_obj_type_t machine_hard_i2c_type = {
     .print = machine_hard_i2c_print,
     .make_new = machine_hard_i2c_make_new,
     .protocol = &machine_hard_i2c_p,
-    .locals_dict = (mp_obj_dict_t *)&mp_machine_soft_i2c_locals_dict,
+    .locals_dict = (mp_obj_dict_t *)&mp_machine_i2c_locals_dict,
 };