tools: kwboot: Add support for backspace key in mini terminal

Marvell BootROM recognize only '\b' byte as backspace. Use terminfo
for retrieving current backspace sequence and replace any occurrence of
backspace sequence by the '\b' byte.

Reading terminfo database is possible via tigetstr() function from system
library libtinfo.so.*. So link kwboot with -ltinfo.

Normally terminfo functions are in <term.h> system header file. But this
header file conflicts with U-Boot "termios_linux.h" header file. So declare
terminfo functions manually.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Stefan Roese <sr@denx.de>
Tested-by: Stefan Roese <sr@denx.de>

tools/Makefile

@@ -197,7 +197,7 @@ hostprogs-$(CONFIG_EXYNOS5420) += mkexynosspl
 HOSTCFLAGS_mkexynosspl.o := -pedantic
 
 HOSTCFLAGS_kwboot.o += -pthread
-HOSTLDLIBS_kwboot += -pthread
+HOSTLDLIBS_kwboot += -pthread -ltinfo
 
 ifdtool-objs := $(LIBFDT_OBJS) ifdtool.o
 hostprogs-$(CONFIG_X86) += ifdtool

tools/kwboot.c

@@ -36,6 +36,13 @@
 #include <termios.h>
 #endif
 
+/*
+ * These functions are in <term.h> header file, but this header file conflicts
+ * with "termios_linux.h" header file. So declare these functions manually.
+ */
+extern int setupterm(const char *, int, int *);
+extern char *tigetstr(const char *);
+
 /*
  * Marvell BootROM UART Sensing
  */
@@ -1376,37 +1383,84 @@ kwboot_xmodem(int tty, const void *_img, size_t size, int baudrate)
 }
 
 static int
-kwboot_term_pipe(int in, int out, const char *quit, int *s)
+kwboot_term_pipe(int in, int out, const char *quit, int *s, const char *kbs, int *k)
 {
 	char buf[128];
-	ssize_t nin;
+	ssize_t nin, noff;
 
 	nin = read(in, buf, sizeof(buf));
 	if (nin <= 0)
 		return -1;
 
-	if (quit) {
+	noff = 0;
+
+	if (quit || kbs) {
 		int i;
 
 		for (i = 0; i < nin; i++) {
-			if (buf[i] == quit[*s]) {
+			if ((quit || kbs) &&
+			    (!quit || buf[i] != quit[*s]) &&
+			    (!kbs || buf[i] != kbs[*k])) {
+				const char *prefix;
+				int plen;
+
+				if (quit && kbs) {
+					prefix = (*s >= *k) ? quit : kbs;
+					plen = (*s >= *k) ? *s : *k;
+				} else if (quit) {
+					prefix = quit;
+					plen = *s;
+				} else {
+					prefix = kbs;
+					plen = *k;
+				}
+
+				if (plen > i && kwboot_write(out, prefix, plen - i) < 0)
+					return -1;
+			}
+
+			if (quit && buf[i] == quit[*s]) {
 				(*s)++;
 				if (!quit[*s]) {
 					nin = (i > *s) ? (i - *s) : 0;
 					break;
 				}
-			} else {
-				if (*s > i && kwboot_write(out, quit, *s - i) < 0)
-					return -1;
+			} else if (quit) {
 				*s = 0;
 			}
+
+			if (kbs && buf[i] == kbs[*k]) {
+				(*k)++;
+				if (!kbs[*k]) {
+					if (i > *k + noff &&
+					    kwboot_write(out, buf + noff, i - *k - noff) < 0)
+						return -1;
+					/*
+					 * Replace backspace key by '\b' (0x08)
+					 * byte which is the only recognized
+					 * backspace byte by Marvell BootROM.
+					 */
+					if (write(out, "\x08", 1) < 0)
+						return -1;
+					noff = i + 1;
+					*k = 0;
+				}
+			} else if (kbs) {
+				*k = 0;
+			}
 		}
 
-		if (i == nin)
-			nin -= (nin > *s) ? *s : nin;
+		if (i == nin) {
+			i = 0;
+			if (quit && i < *s)
+				i = *s;
+			if (kbs && i < *k)
+				i = *k;
+			nin -= (nin > i) ? i : nin;
+		}
 	}
 
-	if (kwboot_write(out, buf, nin) < 0)
+	if (nin > noff && kwboot_write(out, buf + noff, nin - noff) < 0)
 		return -1;
 
 	return 0;
@@ -1415,7 +1469,8 @@ kwboot_term_pipe(int in, int out, const char *quit, int *s)
 static int
 kwboot_terminal(int tty)
 {
-	int rc, in, s;
+	int rc, in, s, k;
+	const char *kbs = NULL;
 	const char *quit = "\34c";
 	struct termios otio, tio;
 
@@ -1434,6 +1489,33 @@ kwboot_terminal(int tty)
 			goto out;
 		}
 
+		/*
+		 * Get sequence for backspace key used by the current
+		 * terminal. Every occurrence of this sequence will be
+		 * replaced by '\b' byte which is the only recognized
+		 * backspace byte by Marvell BootROM.
+		 *
+		 * Note that we cannot read this sequence from termios
+		 * c_cc[VERASE] as VERASE is valid only when ICANON is
+		 * set in termios c_lflag, which is not case for us.
+		 *
+		 * Also most terminals do not set termios c_cc[VERASE]
+		 * as c_cc[VERASE] can specify only one-byte sequence
+		 * and instead let applications to read (possible
+		 * multi-byte) sequence for backspace key from "kbs"
+		 * terminfo database based on $TERM env variable.
+		 *
+		 * So read "kbs" from terminfo database via tigetstr()
+		 * call after successful setupterm(). Most terminals
+		 * use byte 0x7F for backspace key, so replacement with
+		 * '\b' is required.
+		 */
+		if (setupterm(NULL, STDOUT_FILENO, &rc) == 0) {
+			kbs = tigetstr("kbs");
+			if (kbs == (char *)-1)
+				kbs = NULL;
+		}
+
 		kwboot_printv("[Type Ctrl-%c + %c to quit]\r\n",
 			      quit[0] | 0100, quit[1]);
 	} else
@@ -1441,6 +1523,7 @@ kwboot_terminal(int tty)
 
 	rc = 0;
 	s = 0;
+	k = 0;
 
 	do {
 		fd_set rfds;
@@ -1460,13 +1543,13 @@ kwboot_terminal(int tty)
 			break;
 
 		if (FD_ISSET(tty, &rfds)) {
-			rc = kwboot_term_pipe(tty, STDOUT_FILENO, NULL, NULL);
+			rc = kwboot_term_pipe(tty, STDOUT_FILENO, NULL, NULL, NULL, NULL);
 			if (rc)
 				break;
 		}
 
 		if (in >= 0 && FD_ISSET(in, &rfds)) {
-			rc = kwboot_term_pipe(in, tty, quit, &s);
+			rc = kwboot_term_pipe(in, tty, quit, &s, kbs, &k);
 			if (rc)
 				break;
 		}