linux-kernel - [PATCH wireless-next 2/2] ath: dfs_pattern_detector: Use flex array to simplify code

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Message-Id: <1920cc38db2e570633e13b37d50852f3202a7270.1695538105.git.christophe.jaillet@wanadoo.fr>
Date:   Sun, 24 Sep 2023 08:57:50 +0200
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     Kalle Valo <kvalo@...nel.org>
Cc:     linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        linux-wireless@...r.kernel.org
Subject: [PATCH wireless-next 2/2] ath: dfs_pattern_detector: Use flex array to simplify code

At the time of the writing, the value of 'num_radar_types' is 7 or 9. So
on a 64 bits system, only 56 or 72 bytes are allocated for the
'detectors' array.

Turn it into a flex array, in order to simplify memory management and save
an indirection when the array is used.

Doing so, cd->detectors can't be NULL, and channel_detector_exit() can be
simplified as well.

Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
---
Patch #1/2 is a fix, for for wireless.
Patch #2/2 is for wireless-next I guess, but depnds on #1

Not sure if we can mix different target in the same serie. Let me know.
---
 .../net/wireless/ath/dfs_pattern_detector.c   | 21 +++++++------------
 1 file changed, 8 insertions(+), 13 deletions(-)

diff --git a/drivers/net/wireless/ath/dfs_pattern_detector.c b/drivers/net/wireless/ath/dfs_pattern_detector.c
index 2788a1b06c17..700da9f4531e 100644
--- a/drivers/net/wireless/ath/dfs_pattern_detector.c
+++ b/drivers/net/wireless/ath/dfs_pattern_detector.c
@@ -161,7 +161,7 @@ get_dfs_domain_radar_types(enum nl80211_dfs_regions region)
 struct channel_detector {
 	struct list_head head;
 	u16 freq;
-	struct pri_detector **detectors;
+	struct pri_detector *detectors[];
 };
 
 /* channel_detector_reset() - reset detector lines for a given channel */
@@ -183,14 +183,13 @@ static void channel_detector_exit(struct dfs_pattern_detector *dpd,
 	if (cd == NULL)
 		return;
 	list_del(&cd->head);
-	if (cd->detectors) {
-		for (i = 0; i < dpd->num_radar_types; i++) {
-			struct pri_detector *de = cd->detectors[i];
-			if (de != NULL)
-				de->exit(de);
-		}
+
+	for (i = 0; i < dpd->num_radar_types; i++) {
+		struct pri_detector *de = cd->detectors[i];
+		if (de != NULL)
+			de->exit(de);
 	}
-	kfree(cd->detectors);
+
 	kfree(cd);
 }
 
@@ -200,16 +199,12 @@ channel_detector_create(struct dfs_pattern_detector *dpd, u16 freq)
 	u32 i;
 	struct channel_detector *cd;
 
-	cd = kmalloc(sizeof(*cd), GFP_ATOMIC);
+	cd = kzalloc(struct_size(cd, detectors, dpd->num_radar_types), GFP_ATOMIC);
 	if (cd == NULL)
 		goto fail;
 
 	INIT_LIST_HEAD(&cd->head);
 	cd->freq = freq;
-	cd->detectors = kcalloc(dpd->num_radar_types,
-				      sizeof(*cd->detectors), GFP_ATOMIC);
-	if (cd->detectors == NULL)
-		goto fail;
 
 	for (i = 0; i < dpd->num_radar_types; i++) {
 		const struct radar_detector_specs *rs = &dpd->radar_spec[i];
-- 
2.34.1