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From:   Yue Hu <zbestahu@gmail.com>
To:     gregkh@linuxfoundation.org, jslaby@suse.com
Cc:     linux-kernel@vger.kernel.org, huyue2@yulong.com, zbestahu@163.com
Subject: [PATCH] sysrq: use only one slot for loglevels in key table
Date:   Wed, 22 Jul 2020 17:26:09 +0800
Message-Id: <20200722092610.11504-1-zbestahu@gmail.com>
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From: Yue Hu <huyue2@yulong.com>

Currently, sysrq_key_table[] has 10 slots for same interface to change
console loglevel. No specific purpose to do that. Let's use only one slot
to save memory space. Also, update the key2index calculation. And remove
needless code in help message print path to make the logic simpler.

Signed-off-by: Yue Hu <huyue2@yulong.com>
---
 drivers/tty/sysrq.c | 27 +++++----------------------
 1 file changed, 5 insertions(+), 22 deletions(-)

diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
index 7c95afa9..3f12910 100644
--- a/drivers/tty/sysrq.c
+++ b/drivers/tty/sysrq.c
@@ -442,17 +442,8 @@ static void sysrq_handle_unrt(int key)
 /* Key Operations table and lock */
 static DEFINE_SPINLOCK(sysrq_key_table_lock);
 
-static const struct sysrq_key_op *sysrq_key_table[36] = {
-	&sysrq_loglevel_op,		/* 0 */
-	&sysrq_loglevel_op,		/* 1 */
-	&sysrq_loglevel_op,		/* 2 */
-	&sysrq_loglevel_op,		/* 3 */
-	&sysrq_loglevel_op,		/* 4 */
-	&sysrq_loglevel_op,		/* 5 */
-	&sysrq_loglevel_op,		/* 6 */
-	&sysrq_loglevel_op,		/* 7 */
-	&sysrq_loglevel_op,		/* 8 */
-	&sysrq_loglevel_op,		/* 9 */
+static const struct sysrq_key_op *sysrq_key_table[27] = {
+	&sysrq_loglevel_op,		/* 0 - 9 */
 
 	/*
 	 * a: Don't use for system provided sysrqs, it is handled specially on
@@ -507,9 +498,9 @@ static int sysrq_key_table_key2index(int key)
 	int retval;
 
 	if ((key >= '0') && (key <= '9'))
-		retval = key - '0';
+		retval = 0;
 	else if ((key >= 'a') && (key <= 'z'))
-		retval = key + 10 - 'a';
+		retval = key + 1 - 'a';
 	else
 		retval = -1;
 	return retval;
@@ -577,16 +568,8 @@ void __handle_sysrq(int key, bool check_mask)
 		pr_info("HELP : ");
 		/* Only print the help msg once per handler */
 		for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
-			if (sysrq_key_table[i]) {
-				int j;
-
-				for (j = 0; sysrq_key_table[i] !=
-						sysrq_key_table[j]; j++)
-					;
-				if (j != i)
-					continue;
+			if (sysrq_key_table[i])
 				pr_cont("%s ", sysrq_key_table[i]->help_msg);
-			}
 		}
 		pr_cont("\n");
 		console_loglevel = orig_log_level;
-- 
1.9.1