scpi_serial: Reimplement to allow scpi_read_complete() to work correctly.

hardware/common/scpi_serial.c

@@ -26,12 +26,13 @@
 
 #define LOG_PREFIX "scpi_serial"
 
-#define SCPI_READ_RETRIES 100
-#define SCPI_READ_RETRY_TIMEOUT 10000
+#define BUFFER_SIZE 1024
 
 struct scpi_serial {
 	struct sr_serial_dev_inst *serial;
-	char last_character;
+	char buffer[BUFFER_SIZE];
+	size_t count;
+	size_t read;
 };
 
 static int scpi_serial_dev_inst_new(void *priv, const char *resource,
@@ -58,6 +59,9 @@ static int scpi_serial_open(void *priv)
 	if (serial_flush(serial) != SR_OK)
 		return SR_ERR;
 
+	sscpi->count = 0;
+	sscpi->read = 0;
+
 	return SR_OK;
 }
 
@@ -107,9 +111,7 @@ static int scpi_serial_send(void *priv, const char *command)
 
 static int scpi_serial_read_begin(void *priv)
 {
-	struct scpi_serial *sscpi = priv;
-
-	sscpi->last_character = '\0';
+	(void) priv;
 
 	return SR_OK;
 }
@@ -117,27 +119,56 @@ static int scpi_serial_read_begin(void *priv)
 static int scpi_serial_read_data(void *priv, char *buf, int maxlen)
 {
 	struct scpi_serial *sscpi = priv;
-	int ret;
+	int len, ret;
 
-	ret = serial_read(sscpi->serial, buf, maxlen);
+	len = BUFFER_SIZE - sscpi->count;
 
-	if (ret < 0)
-		return ret;
+	/* Try to read new data into the buffer if there is space. */
+	if (len > 0) {
+		ret = serial_read(sscpi->serial, sscpi->buffer + sscpi->read,
+				BUFFER_SIZE - sscpi->count);
 
-	if (ret > 0) {
-		sscpi->last_character = buf[ret - 1];
-		if (sscpi->last_character == '\n')
-			ret--;
+		if (ret < 0)
+			return ret;
+
+		sscpi->count += ret;
+
+		if (ret > 0)
+			sr_spew("Read %d bytes into buffer.", ret);
 	}
 
-	return ret;
+	/* Return as many bytes as possible from buffer, excluding any trailing newline. */
+	if (sscpi->read < sscpi->count) {
+		len = sscpi->count - sscpi->read;
+		if (len > maxlen)
+			len = maxlen;
+		if (sscpi->buffer[sscpi->read + len - 1] == '\n')
+			len--;
+		sr_spew("Returning %d bytes from buffer.", len);
+		memcpy(buf, sscpi->buffer + sscpi->read, len);
+		sscpi->read += len;
+		if (sscpi->read == BUFFER_SIZE) {
+			sr_spew("Resetting buffer.");
+			sscpi->count = 0;
+			sscpi->read = 0;
+		}
+		return len;
+	}
+
+	return 0;
 }
 
 static int scpi_serial_read_complete(void *priv)
 {
 	struct scpi_serial *sscpi = priv;
 
-	return (sscpi->last_character == '\n');
+	/* If the next character is a newline, discard it and report complete. */
+	if (sscpi->read < sscpi->count && sscpi->buffer[sscpi->read] == '\n') {
+		sscpi->read++;
+		return 1;
+	} else {
+		return 0;
+	}
 }
 
 static int scpi_serial_close(void *priv)