[kvm-unit-tests PATCH v2 3/6] s390x: Add linemode buffer to fix newline on every print

[Janosch Frank <frankja@linux.ibm.com>]

Linemode seems to add a newline for each sent message which makes
reading rather hard. Hence we add a small buffer and only print if
it's full or a newline is encountered. Except for when the string is
longer than the buffer, then we flush the buffer and print directly.

Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
---
 lib/s390x/sclp-console.c | 70 +++++++++++++++++++++++++++++++++++++---
 1 file changed, 66 insertions(+), 4 deletions(-)

diff --git a/lib/s390x/sclp-console.c b/lib/s390x/sclp-console.c
index 19416b5..7397dc1 100644
--- a/lib/s390x/sclp-console.c
+++ b/lib/s390x/sclp-console.c
@@ -13,6 +13,7 @@
 #include <asm/page.h>
 #include <asm/arch_def.h>
 #include <asm/io.h>
+#include <asm/spinlock.h>
 #include "sclp.h"
 
 /*
@@ -87,6 +88,10 @@ static uint8_t _ascebc[256] = {
      0x90, 0x3F, 0x3F, 0x3F, 0x3F, 0xEA, 0x3F, 0xFF
 };
 
+static char lm_buff[120];
+static unsigned char lm_buff_off;
+static struct spinlock lm_buff_lock;
+
 static void sclp_print_ascii(const char *str)
 {
 	int len = strlen(str);
@@ -103,10 +108,10 @@ static void sclp_print_ascii(const char *str)
 	sclp_service_call(SCLP_CMD_WRITE_EVENT_DATA, sccb);
 }
 
-static void sclp_print_lm(const char *str)
+static void lm_print(const char *buff, int len)
 {
 	unsigned char *ptr, *end, ch;
-	unsigned int count, offset, len;
+	unsigned int count, offset;
 	struct WriteEventData *sccb;
 	struct mdb *mdb;
 	struct mto *mto;
@@ -117,11 +122,10 @@ static void sclp_print_lm(const char *str)
 	end = (unsigned char *) sccb + 4096 - 1;
 	memset(sccb, 0, sizeof(*sccb));
 	ptr = (unsigned char *) &sccb->msg.mdb.mto;
-	len = strlen(str);
 	offset = 0;
 	do {
 		for (count = sizeof(*mto); offset < len; count++) {
-			ch = str[offset++];
+			ch = buff[offset++];
 			if (ch == 0x0a || ptr + count > end)
 				break;
 			ptr[count] = _ascebc[ch];
@@ -148,6 +152,64 @@ static void sclp_print_lm(const char *str)
 	sclp_service_call(SCLP_CMD_WRITE_EVENT_DATA, sccb);
 }
 
+
+/*
+ * In contrast to the ascii console, linemode produces a new
+ * line with every write of data. The report() function uses
+ * several printf() calls to generate a line of data which
+ * would all end up on different lines.
+ *
+ * Hence we buffer here until we encounter a \n or the buffer
+ * is full. That means that linemode output can look a bit
+ * different from ascii and that it takes a bit longer for
+ * lines to appear.
+ */
+static void sclp_print_lm(const char *str)
+{
+	int len;
+	char *nl;
+
+	spin_lock(&lm_buff_lock);
+
+	len = strlen(str);
+	/*
+	 * No use in copying into lm_buff, its time to flush the
+	 * buffer and print str until finished.
+	 */
+	if (len > sizeof(lm_buff)) {
+		if (lm_buff_off)
+			lm_print(lm_buff, lm_buff_off);
+		lm_print(str, len);
+		memset(lm_buff, 0 , sizeof(lm_buff));
+		lm_buff_off = 0;
+		goto out;
+	}
+
+fill:
+	len = len < (sizeof(lm_buff) - lm_buff_off) ? len : (sizeof(lm_buff) - lm_buff_off);
+	if ((lm_buff_off < sizeof(lm_buff) - 1)) {
+		memcpy(&lm_buff[lm_buff_off], str, len);
+		lm_buff_off += len;
+	}
+	/* Buffer not full and no newline */
+	nl = strchr(lm_buff, '\n');
+	if (lm_buff_off != sizeof(lm_buff) - 1 && !nl)
+		goto out;
+
+	lm_print(lm_buff, lm_buff_off);
+	memset(lm_buff, 0 , sizeof(lm_buff));
+	lm_buff_off = 0;
+
+	if (len < strlen(str)) {
+		str = &str[len];
+		len = strlen(str);
+		goto fill;
+	}
+
+out:
+	spin_unlock(&lm_buff_lock);
+}
+
 /*
  * SCLP needs to be initialized by setting a send and receive mask,
  * indicating which messages the control program (we) want(s) to
-- 
2.17.0