linux-kernel - [PATCH v2] ath5k: fix WARNING opportunity for swap.

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Message-Id: <20230815040819.649455-1-mahmoudmatook.mm@gmail.com>
Date:   Tue, 15 Aug 2023 08:08:19 +0400
From:   Mahmoud Maatuq <mahmoudmatook.mm@...il.com>
To:     jirislaby@...nel.org, mickflemm@...il.com, mcgrof@...nel.org,
        kvalo@...nel.org, linux-wireless@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     linux-kernel-mentees@...ts.linuxfoundation.org,
        Mahmoud Maatuq <mahmoudmatook.mm@...il.com>
Subject: [PATCH v2] ath5k: fix WARNING opportunity for swap.

coccinielle reported the following:
./drivers/net/wireless/ath/ath5k/phy.c:1573:25-26: WARNING opportunity for swap()

while trying to fix the above warning, it reveals that ath5k_hw_get_median_noise_floor() 
had open-coded sort() functionality. Since ath5k_hw_get_median_noise_floor() only
executes once every 10 seconds, any extra overhead due to sort() calling
its "compare" and "swap" functions can be ignored, so replace the
existing logic with a call to sort().

Signed-off-by: Mahmoud Maatuq <mahmoudmatook.mm@...il.com>
Suggested-by: Jiri Slaby <jirislaby@...nel.org>
---
changes in v2:
- update the commit message explaining why open-coded sort()
  functionality is replaced with a call to sort().

- this part of updating the commit message is suggested by
   Jeff Johnson <quic_jjohnson@...cinc.com>

changes in v1:
- replace the entire double loop with sort()
  as suggested by Jiri Slaby <jirislaby@...nel.org>
---
 drivers/net/wireless/ath/ath5k/phy.c | 29 +++++++++++++---------------
 1 file changed, 13 insertions(+), 16 deletions(-)

diff --git a/drivers/net/wireless/ath/ath5k/phy.c b/drivers/net/wireless/ath/ath5k/phy.c
index 5797ef9c73d7..7ee4e1616f45 100644
--- a/drivers/net/wireless/ath/ath5k/phy.c
+++ b/drivers/net/wireless/ath/ath5k/phy.c
@@ -26,6 +26,7 @@
 
 #include <linux/delay.h>
 #include <linux/slab.h>
+#include <linux/sort.h>
 #include <asm/unaligned.h>
 
 #include "ath5k.h"
@@ -1554,6 +1555,11 @@ static void ath5k_hw_update_nfcal_hist(struct ath5k_hw *ah, s16 noise_floor)
 	hist->nfval[hist->index] = noise_floor;
 }
 
+static int cmps16(const void *a, const void *b)
+{
+	return *(s16 *)a - *(s16 *)b;
+}
+
 /**
  * ath5k_hw_get_median_noise_floor() - Get median NF from history buffer
  * @ah: The &struct ath5k_hw
@@ -1561,25 +1567,16 @@ static void ath5k_hw_update_nfcal_hist(struct ath5k_hw *ah, s16 noise_floor)
 static s16
 ath5k_hw_get_median_noise_floor(struct ath5k_hw *ah)
 {
-	s16 sort[ATH5K_NF_CAL_HIST_MAX];
-	s16 tmp;
-	int i, j;
-
-	memcpy(sort, ah->ah_nfcal_hist.nfval, sizeof(sort));
-	for (i = 0; i < ATH5K_NF_CAL_HIST_MAX - 1; i++) {
-		for (j = 1; j < ATH5K_NF_CAL_HIST_MAX - i; j++) {
-			if (sort[j] > sort[j - 1]) {
-				tmp = sort[j];
-				sort[j] = sort[j - 1];
-				sort[j - 1] = tmp;
-			}
-		}
-	}
+	s16 sorted_nfval[ATH5K_NF_CAL_HIST_MAX];
+	int i;
+
+	memcpy(sorted_nfval, ah->ah_nfcal_hist.nfval, sizeof(sorted_nfval));
+	sort(sorted_nfval, ATH5K_NF_CAL_HIST_MAX, sizeof(s16), cmps16, NULL);
 	for (i = 0; i < ATH5K_NF_CAL_HIST_MAX; i++) {
 		ATH5K_DBG(ah, ATH5K_DEBUG_CALIBRATE,
-			"cal %d:%d\n", i, sort[i]);
+			"cal %d:%d\n", i, sorted_nfval[i]);
 	}
-	return sort[(ATH5K_NF_CAL_HIST_MAX - 1) / 2];
+	return sorted_nfval[(ATH5K_NF_CAL_HIST_MAX - 1) / 2];
 }
 
 /**
-- 
2.34.1