extmod/virtpin: Initial implementation of open-ended C-level Pin interface.

Using usual method of virtual method tables. Single virtual method,
ioctl, is defined currently for all operations. This universal and
extensible vtable-based method is also defined as a default MPHAL
GPIO implementation, but a specific port may override it with its
own implementation (e.g. close-ended, but very efficient, e.g. avoiding
virtual method dispatch).

extmod/virtpin.c

+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2016 Paul Sokolovsky
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "extmod/virtpin.h"
+
+int mp_virtual_pin_read(mp_obj_t pin) {
+    mp_obj_base_t* s = (mp_obj_base_t*)MP_OBJ_TO_PTR(pin);
+    mp_pin_p_t *pin_p = (mp_pin_p_t*)s->type->stream_p;
+    return pin_p->ioctl(pin, MP_PIN_READ, 0, NULL);
+}
+
+void mp_virtual_pin_write(mp_obj_t pin, int value) {
+    mp_obj_base_t* s = (mp_obj_base_t*)MP_OBJ_TO_PTR(pin);
+    mp_pin_p_t *pin_p = (mp_pin_p_t*)s->type->stream_p;
+    pin_p->ioctl(pin, MP_PIN_WRITE, value, NULL);
+}

extmod/virtpin.h

+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2016 Paul Sokolovsky
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "py/obj.h"
+
+#define MP_PIN_READ   (1)
+#define MP_PIN_WRITE  (2)
+#define MP_PIN_INPUT  (3)
+#define MP_PIN_OUTPUT (4)
+
+// Pin protocol
+typedef struct _mp_pin_p_t {
+    mp_uint_t (*ioctl)(mp_obj_t obj, mp_uint_t request, uintptr_t arg, int *errcode);
+} mp_pin_p_t;
+
+int mp_virtual_pin_read(mp_obj_t pin);
+void mp_virtual_pin_write(mp_obj_t pin, int value);

py/mphal.h

@@ -66,4 +66,13 @@ mp_uint_t mp_hal_ticks_ms(void);
 mp_uint_t mp_hal_ticks_us(void);
 #endif
 
+// If port HAL didn't define its own pin API, use generic
+// "virtual pin" API from the core.
+#ifndef mp_hal_pin_obj_t
+#define mp_hal_pin_obj_t mp_obj_t
+#define mp_hal_get_pin_obj(pin) (pin)
+#define mp_hal_pin_read(pin) mp_virtual_pin_read(pin)
+#define mp_hal_pin_write(pin, v) mp_virtual_pin_write(pin, v)
+#endif
+
 #endif // __MICROPY_INCLUDED_PY_MPHAL_H__

py/py.mk

@@ -174,6 +174,7 @@ PY_O_BASENAME = \
 	../extmod/moduheapq.o \
 	../extmod/moduhashlib.o \
 	../extmod/modubinascii.o \
+	../extmod/virtpin.o \
 	../extmod/machine_mem.o \
 	../extmod/machine_i2c.o \
 	../extmod/modussl.o \