[fluksod] implement spi read operation in C

mote/v2/openwrt/package/flukso/luasrc/flukso/spi.lua

@@ -110,21 +110,8 @@ function tx(msg, cdev)
 end
 
 function rx(msg, cdev)
-	local sequence = {}
-
-	for char in function() return cdev:read(1) end do
-		if char ~= '\0' then
-			table.insert(sequence, char)
-		else
-        	        -- one more read to let the AVR send a second 0x00
-			-- after which the AVR's state machine toggles to read mode
-			cdev:read(1)
-			break
-		end
-	end
-
 	msg.received = {}
-	msg.received.raw = table.concat(sequence)
+	msg.received.raw = cdev:spiread()
 	msg.received.l, msg.received.u = msg.received.raw:match('^l(%w*)%.?u(%w*)%.?$')
 
 	if msg.received.l ~= '' and msg.received.l:sub(1, 2) == msg.parsed[1] then

mote/v2/openwrt/package/luci/libs/nixio/src/file.c

@@ -223,6 +223,68 @@ static int nixio_file_read(lua_State *L) {
 	}
 }
 
+static int nixio_file_spi_read(lua_State *L) {
+	int fd = nixio__checkfd(L, 1);
+	char buffer[NIXIO_BUFFERSIZE];
+	int readc;
+	size_t len;
+	char last = 0;
+
+	for (size_t i = 0; i < NIXIO_BUFFERSIZE; i++) {
+		do {
+			readc = read(fd, buffer + i, 1);
+		} while (readc == -1 && errno == EINTR);
+
+		if (readc < 0) {
+			return nixio__perror(L);
+		}
+
+		if (last) {
+			break;
+		}
+
+		if (buffer[i] == 0x00) {
+			len = i;
+			last = 1; /* one last pass through the for loop to sync the state machine */
+
+		}
+	}
+
+/* REVISIT: a read on spidev doens't work for numbytes > 1 */
+
+/*	for (size_t i = 0; i < NIXIO_BUFFERSIZE; i += 2) {
+		do {
+			readc = read(fd, buffer + i, 2);
+		} while (readc == -1 && errno == EINTR);
+
+		if (readc < 0) {
+			return nixio__perror(L);
+		}
+
+		if (buffer[i + 1] == 0x00) {
+			len = i;
+
+			if (buffer[i] != 0x00) {
+				len = i + 1;
+
+				do {
+					readc = read(fd, buffer + i + 2, 1);
+				} while (readc == -1 && errno == EINTR);
+
+				if (readc < 0) {
+					return nixio__perror(L);
+				}
+			}
+
+			break;
+		}
+			
+	}
+*/
+
+	lua_pushlstring(L, buffer, len);
+	return 1;
+}
 
 static int nixio_file_seek(lua_State *L) {
 	int fd = nixio__checkfd(L, 1);
@@ -350,6 +412,7 @@ static int nixio_file__tostring(lua_State *L) {
 static const luaL_reg M[] = {
 	{"write",		nixio_file_write},
 	{"read",		nixio_file_read},
+	{"spiread",		nixio_file_spi_read},
 	{"tell",		nixio_file_tell},
 	{"seek",		nixio_file_seek},
 	{"stat",		nixio_file_stat},