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authorDaniel Thompson <daniel.thompson@linaro.org>2019-10-25 08:33:25 +0100
committerDaniel Thompson <daniel.thompson@linaro.org>2019-10-28 12:02:21 +0000
commitd04213af90935d8b247c1327c9ea142fc037165f (patch)
treeacb625f166ec6fdffb70bda937c4bf9fc8305c85 /kernel
parent53b63136e81220cb2f8b541c03a1df9199896821 (diff)
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kdb: Simplify code to fetch characters from console
Currently kdb_read_get_key() contains complex control flow that, on close inspection, turns out to be unnecessary. In particular: 1. It is impossible to enter the branch conditioned on (escape_delay == 1) except when the loop enters with (escape_delay == 2) allowing us to combine the branches. 2. Most of the code conditioned on (escape_delay == 2) simply modifies local data and then breaks out of the loop causing the function to return escape_data[0]. 3. Based on #2 there is not actually any need to ever explicitly set escape_delay to 2 because we it is much simpler to directly return escape_data[0] instead. 4. escape_data[0] is, for all but one exit path, known to be '\e'. Simplify the code based on these observations. There is a subtle (and harmless) change of behaviour resulting from this simplification: instead of letting the escape timeout after ~1998 milliseconds we now timeout after ~2000 milliseconds Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org> Reviewed-by: Douglas Anderson <dianders@chromium.org> Link: https://lore.kernel.org/r/20191025073328.643-3-daniel.thompson@linaro.org
Diffstat (limited to 'kernel')
-rw-r--r--kernel/debug/kdb/kdb_io.c38
1 files changed, 14 insertions, 24 deletions
diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c
index cfc054fd8097..a92ceca29637 100644
--- a/kernel/debug/kdb/kdb_io.c
+++ b/kernel/debug/kdb/kdb_io.c
@@ -124,25 +124,18 @@ static int kdb_read_get_key(char *buffer, size_t bufsize)
touch_nmi_watchdog();
f = &kdb_poll_funcs[0];
}
- if (escape_delay == 2) {
- *ped = '\0';
- ped = escape_data;
- --escape_delay;
- }
- if (escape_delay == 1) {
- key = *ped++;
- if (!*ped)
- --escape_delay;
- break;
- }
+
key = (*f)();
+
if (key == -1) {
if (escape_delay) {
udelay(ESCAPE_UDELAY);
- --escape_delay;
+ if (--escape_delay == 0)
+ return '\e';
}
continue;
}
+
if (bufsize <= 2) {
if (key == '\r')
key = '\n';
@@ -150,27 +143,24 @@ static int kdb_read_get_key(char *buffer, size_t bufsize)
*buffer = '\0';
return -1;
}
+
if (escape_delay == 0 && key == '\e') {
escape_delay = ESCAPE_DELAY;
ped = escape_data;
f_escape = f;
}
if (escape_delay) {
- *ped++ = key;
- if (f_escape != f) {
- escape_delay = 2;
- continue;
- }
+ if (f_escape != f)
+ return '\e';
+ *ped++ = key;
key = kdb_handle_escape(escape_data, ped - escape_data);
- if (key > 0) {
- escape_data[0] = key;
- escape_data[1] = '\0';
- }
- if (key)
- escape_delay = 2;
- continue;
+ if (key < 0)
+ return '\e';
+ if (key == 0)
+ continue;
}
+
break; /* A key to process */
}
return key;