test: serial: Add test for putc/puts

This adds a test to ensure that puts is equivalent to putc called in a
loop. We don't verify the contents of the message to avoid having to
record console output a second time (though that could be added in the
future). The globals are initialized to non-zero values to avoid a
warning; in particular, the character count is off-by-one (but we always
make relative measurements).

Signed-off-by: Sean Anderson <sean.anderson@seco.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

arch/sandbox/include/asm/serial.h

@@ -16,6 +16,28 @@ struct sandbox_serial_plat {
 	int colour;	/* Text colour to use for output, -1 for none */
 };
 
+/**
+ * sandbox_serial_written() - Get the total number of characters written
+ *
+ * This returns the number of characters written by the sandbox serial
+ * device. It is intended for performing tests of the serial subsystem
+ * where a console buffer cannot be used. The absolute number should not be
+ * relied upon; call this function twice and compare the difference.
+ *
+ * Return: The number of characters written
+ */
+size_t sandbox_serial_written(void);
+
+/**
+ * sandbox_serial_endisable() - Enable or disable serial output
+ * @enabled: Whether serial output should be enabled or not
+ *
+ * This allows tests to enable or disable the sandbox serial output. All
+ * processes relating to writing output (except the actual writing) will be
+ * performed.
+ */
+void sandbox_serial_endisable(bool enabled);
+
 /**
  * struct sandbox_serial_priv - Private data for this driver
  *

drivers/serial/sandbox.c

@@ -23,6 +23,19 @@
 
 DECLARE_GLOBAL_DATA_PTR;
 
+static size_t _sandbox_serial_written = 1;
+static bool sandbox_serial_enabled = true;
+
+size_t sandbox_serial_written(void)
+{
+	return _sandbox_serial_written;
+}
+
+void sandbox_serial_endisable(bool enabled)
+{
+	sandbox_serial_enabled = enabled;
+}
+
 /**
  * output_ansi_colour() - Output an ANSI colour code
  *
@@ -84,11 +97,14 @@ static int sandbox_serial_putc(struct udevice *dev, const char ch)
 {
 	struct sandbox_serial_priv *priv = dev_get_priv(dev);
 
-	sandbox_print_color(dev);
-	os_write(1, &ch, 1);
 	if (ch == '\n')
 		priv->start_of_line = true;
 
+	if (sandbox_serial_enabled) {
+		sandbox_print_color(dev);
+		os_write(1, &ch, 1);
+	}
+	_sandbox_serial_written += 1;
 	return 0;
 }
 
@@ -96,12 +112,21 @@ static ssize_t sandbox_serial_puts(struct udevice *dev, const char *s,
 				   size_t len)
 {
 	struct sandbox_serial_priv *priv = dev_get_priv(dev);
+	ssize_t ret;
 
-	sandbox_print_color(dev);
 	if (s[len - 1] == '\n')
 		priv->start_of_line = true;
 
-	return os_write(1, s, len);
+	if (sandbox_serial_enabled) {
+		sandbox_print_color(dev);
+		ret = os_write(1, s, len);
+		if (ret < 0)
+			return ret;
+	} else {
+		ret = len;
+	}
+	_sandbox_serial_written += ret;
+	return ret;
 }
 
 static int sandbox_serial_pending(struct udevice *dev, bool input)

test/dm/serial.c

@@ -7,14 +7,22 @@
 #include <log.h>
 #include <serial.h>
 #include <dm.h>
+#include <asm/serial.h>
 #include <dm/test.h>
 #include <test/test.h>
 #include <test/ut.h>
 
+static const char test_message[] =
+	"This is a test message\n"
+	"consisting of multiple lines\n";
+
 static int dm_test_serial(struct unit_test_state *uts)
 {
+	int i;
 	struct serial_device_info info_serial = {0};
 	struct udevice *dev_serial;
+	size_t start, putc_written;
+
 	uint value_serial;
 
 	ut_assertok(uclass_get_device_by_name(UCLASS_SERIAL, "serial",
@@ -66,6 +74,17 @@ static int dm_test_serial(struct unit_test_state *uts)
 						   SERIAL_8_BITS,
 						   SERIAL_TWO_STOP)));
 
+	/* Verify that putc and puts print the same number of characters */
+	sandbox_serial_endisable(false);
+	start = sandbox_serial_written();
+	for (i = 0; i < sizeof(test_message) - 1; i++)
+		serial_putc(test_message[i]);
+	putc_written = sandbox_serial_written();
+	serial_puts(test_message);
+	sandbox_serial_endisable(true);
+	ut_asserteq(putc_written - start,
+		    sandbox_serial_written() - putc_written);
+
 	return 0;
 }