linux-kernel - [PATCH v2 5/5] kdb: Tweak escape handling for vi users

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Message-Id: <20191008132043.7966-6-daniel.thompson@linaro.org>
Date:   Tue,  8 Oct 2019 14:20:43 +0100
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Jason Wessel <jason.wessel@...driver.com>,
        Douglas Anderson <dianders@...omium.org>
Cc:     Daniel Thompson <daniel.thompson@...aro.org>,
        kgdb-bugreport@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
        patches@...aro.org
Subject: [PATCH v2 5/5] kdb: Tweak escape handling for vi users

Currently if sequences such as "\ehelp\r" are delivered to the console then
the h gets eaten by the escape handling code. Since pressing escape
becomes something of a nervous twitch for vi users (and that escape doesn't
have much effect at a shell prompt) it is more helpful to emit the 'h' than
the '\e'.

We don't simply choose to emit the final character for all escape sequences
since that will do odd things for unsupported escape sequences (in
other words we retain the existing behaviour once we see '\e[').

Signed-off-by: Daniel Thompson <daniel.thompson@...aro.org>
---
 kernel/debug/kdb/kdb_io.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c
index 288dd1babf90..b3fb88b1ee34 100644
--- a/kernel/debug/kdb/kdb_io.c
+++ b/kernel/debug/kdb/kdb_io.c
@@ -158,8 +158,8 @@ static int kdb_getchar(void)

 		*pbuf++ = key;
 		key = kdb_read_handle_escape(buf, pbuf - buf);
-		if (key < 0) /* no escape sequence; return first character */
-			return buf[0];
+		if (key < 0) /* no escape sequence; return best character */
+			return buf[pbuf - buf != 2 ? 0 : 1];
 		if (key > 0)
 			return key;
 	}
-- 
2.21.0