extmod: Add machine_spi with generic SPI C-protocol and helper methods.

The idea is that all ports can use these helper methods and only need to
provide initialisation of the SPI bus, as well as a single transfer
function.  The coding pattern follows the stream protocol and helper
methods.

extmod/machine_spi.c

@@ -0,0 +1,85 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2016 Damien P. George
+ *
+ * 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 <stdio.h>
+
+#include "py/runtime.h"
+#include "extmod/machine_spi.h"
+
+#if MICROPY_PY_MACHINE_SPI
+
+STATIC void mp_machine_spi_transfer(mp_obj_t self, size_t slen, const uint8_t *src, size_t dlen, uint8_t *dest) {
+    mp_obj_base_t *s = (mp_obj_base_t*)MP_OBJ_TO_PTR(self);
+    mp_machine_spi_p_t *spi_p = (mp_machine_spi_p_t*)s->type->protocol;
+    spi_p->transfer(s, slen, src, dlen, dest);
+}
+
+STATIC mp_obj_t mp_machine_spi_read(size_t n_args, const mp_obj_t *args) {
+    uint8_t write_byte = 0;
+    if (n_args == 3) {
+        write_byte = mp_obj_get_int(args[2]);
+    }
+    vstr_t vstr;
+    vstr_init_len(&vstr, mp_obj_get_int(args[1]));
+    mp_machine_spi_transfer(args[0], 1, &write_byte, vstr.len, (uint8_t*)vstr.buf);
+    return mp_obj_new_str_from_vstr(&mp_type_bytes, &vstr);
+}
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_machine_spi_read_obj, 2, 3, mp_machine_spi_read);
+
+STATIC mp_obj_t mp_machine_spi_readinto(size_t n_args, const mp_obj_t *args) {
+    mp_buffer_info_t bufinfo;
+    mp_get_buffer_raise(args[1], &bufinfo, MP_BUFFER_WRITE);
+    uint8_t write_byte = 0;
+    if (n_args == 3) {
+        write_byte = mp_obj_get_int(args[2]);
+    }
+    mp_machine_spi_transfer(args[0], 1, &write_byte, bufinfo.len, (uint8_t*)bufinfo.buf);
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_machine_spi_readinto_obj, 2, 3, mp_machine_spi_readinto);
+
+STATIC mp_obj_t mp_machine_spi_write(mp_obj_t self, mp_obj_t wr_buf) {
+    mp_buffer_info_t src;
+    mp_get_buffer_raise(wr_buf, &src, MP_BUFFER_READ);
+    mp_machine_spi_transfer(self, src.len, (const uint8_t*)src.buf, 0, NULL);
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_2(mp_machine_spi_write_obj, mp_machine_spi_write);
+
+STATIC mp_obj_t mp_machine_spi_write_readinto(mp_obj_t self, mp_obj_t wr_buf, mp_obj_t rd_buf) {
+    mp_buffer_info_t src;
+    mp_get_buffer_raise(wr_buf, &src, MP_BUFFER_READ);
+    mp_buffer_info_t dest;
+    mp_get_buffer_raise(rd_buf, &dest, MP_BUFFER_WRITE);
+    if (src.len != dest.len) {
+        nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError, "buffers must be the same length"));
+    }
+    mp_machine_spi_transfer(self, src.len, (const uint8_t*)src.buf, dest.len, (uint8_t*)dest.buf);
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_3(mp_machine_spi_write_readinto_obj, mp_machine_spi_write_readinto);
+
+#endif // MICROPY_PY_MACHINE_SPI

extmod/machine_spi.h

@@ -0,0 +1,42 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2016 Damien P. George
+ *
+ * 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.
+ */
+
+#ifndef MICROPY_INCLUDED_EXTMOD_MACHINE_SPI_H
+#define MICROPY_INCLUDED_EXTMOD_MACHINE_SPI_H
+
+#include "py/obj.h"
+
+// SPI protocol
+typedef struct _mp_machine_spi_p_t {
+    void (*transfer)(mp_obj_base_t *obj, size_t slen, const uint8_t *src, size_t dlen, uint8_t *dest);
+} mp_machine_spi_p_t;
+
+MP_DECLARE_CONST_FUN_OBJ(mp_machine_spi_read_obj);
+MP_DECLARE_CONST_FUN_OBJ(mp_machine_spi_readinto_obj);
+MP_DECLARE_CONST_FUN_OBJ(mp_machine_spi_write_obj);
+MP_DECLARE_CONST_FUN_OBJ(mp_machine_spi_write_readinto_obj);
+
+#endif // MICROPY_INCLUDED_EXTMOD_MACHINE_SPI_H

py/mpconfig.h

@@ -923,6 +923,10 @@ typedef double mp_float_t;
 #define MICROPY_PY_MACHINE_I2C (0)
 #endif
 
+#ifndef MICROPY_PY_MACHINE_SPI
+#define MICROPY_PY_MACHINE_SPI (0)
+#endif
+
 #ifndef MICROPY_PY_USSL
 #define MICROPY_PY_USSL (0)
 #endif

py/py.mk

@@ -208,6 +208,7 @@ PY_O_BASENAME = \
 	../extmod/machine_pinbase.o \
 	../extmod/machine_pulse.o \
 	../extmod/machine_i2c.o \
+	../extmod/machine_spi.o \
 	../extmod/modussl_axtls.o \
 	../extmod/modurandom.o \
 	../extmod/modwebsocket.o \