Update redtty_test as a tool for STM dummy driver

2 files changed, 79 insertions, 2 deletions

diff --git a/README b/README
index 3182df3..9ad3b23 100644
--- a/README
+++ b/README
@@ -30,6 +30,17 @@ How to Build:
 	. to test param_array.c
  - make EXTRA_DEBUG_MSG=yes async_test
 	. to test async_veri.c
+ - make EXTRA_DEBUG_MSG=yes redtty_test
+	. to test redirect_ttyprintk.c
+
+4. redtty_test is a useful tool to assist STM Dummy driver testing. It uses
+   /dev/ttyprintk as the message output channel for STM Dummy device. When
+   enabled (./redtty_test on), all message to STM Dummy driver will be
+   redirect to /dev/ttyprintk, who will then write these message to kernel log.
+   And user can view these messages using kernel log tool, such as dmesg.
+
+Usage: please run ./redtty_test with no args:
+$ ./redtty_test
 
 ################################################################################
 How to use:
diff --git a/redirect_ttyprintk.c b/redirect_ttyprintk.c
index e27554a..2862807 100644
--- a/redirect_ttyprintk.c
+++ b/redirect_ttyprintk.c
@@ -11,10 +11,12 @@
 #include <stdio.h>
 #include <sys/ioctl.h>
 #include <unistd.h>
+#include <string.h>
 
 #include "test_commands.h"
 
 #define N_TRACESINK     23      /* Trace data routing for MIPI P1149.7 */
+#define N_TTY 0
 
 /* Open /dev/ttyprintk, and attach N_TRACESINK line discipline to it.
  * Input:
@@ -31,7 +33,10 @@ int redirect_ttyprintk(void)
 
 	fd = open("/dev/ttyprintk", O_WRONLY | O_NOCTTY);
 	if (fd == -1) {
-		TDBG("Failed to open /dev/ttyprintk.\n");
+		printf("Failed to open /dev/ttyprintk.\n");
+		printf("Please check whether /dev/ttyprink exists.\n");
+		printf("If not, please rebuild kernel with "
+						"CONFIG_TTY_PRINTK=y\n");
 		return -1;
 	}
 
@@ -49,9 +54,70 @@ int redirect_ttyprintk(void)
 	return fd;
 }
 
-/* To check underlining STM device is dummy driver?
+/* Open /dev/ttyprintk, and attach N_TTY line discipline to it.
+ * Input:
+ *   none
+ * Return:
+ *   -1: Failure, otherwise
+ *   fd: file discriptor of /dev/ttyprintk
  */
+int restore_ttyprintk(void)
+{
+	int fd;
+	int ldisc;
+	int ret;
+
+	fd = open("/dev/ttyprintk", O_WRONLY | O_NOCTTY);
+	if (fd == -1) {
+		printf("Failed to open /dev/ttyprintk.\n");
+		printf("Please check whether /dev/ttyprink exists.\n");
+		printf("If not, please rebuild kernel with "
+						"CONFIG_TTY_PRINTK=y\n");
+		return -1;
+	}
+
+	/* N_TTY line discipline will be attached to
+	 * the ttyprintk serial port, /dev/ttyprintk
+	 */
+	ldisc = N_TTY;
+	ret = ioctl(fd, TIOCSETD, &ldisc);
+	if (ret == -1) {
+		TDBG("Failed to attach N_TTY to /dev/ttyprintk.\n");
+		close(fd);
+		return ret;
+	}
+
+	return fd;
+}
 
 #ifdef REDTTY_TEST_STUB
 
+extern FILE *stdin;
+
+/* main(), entry point */
+int main(int argc, char** argv)
+{
+	int fd_ttyprintk = -1;
+	char buf[10];
+
+	/* Attach N_TRACESINK to /dev/ttyprink */
+	fd_ttyprintk = redirect_ttyprintk();
+	if (fd_ttyprintk == -1) {
+		printf("Error: failed to open and redirect "
+							"/dev/ttyprintk\n");
+		return -1;
+	}
+	TDBG("Succeed to attach N_TRACESINK to /dev/ttyprintk.\n");
+
+	/* wait for some user input */
+	printf("You can start to test now. And type in any string to quit.\n");
+	fgets(buf, 10, stdin);
+
+	/* close ttyprintk */
+	if (fd_ttyprintk != -1)
+		close(fd_ttyprintk);
+
+	/* return */
+	return 0;
+}
 #endif