[PATCH] ALSA: control_led: fix stack frame usage over 1024 bytes in snd_ctl_led_get()

[Takashi Sakamoto]

GCC warns that snd_ctl_led_get() uses stack frame over 1024 bytes.

control_led.c: In function ‘snd_ctl_led_get’:
control_led.c:128:1: warning: the frame size of 1504 bytes is larger than 1024 bytes [-Wframe-larger-than=]

When taking care of convension in Linux kernel development. it's preferable
to suppress too large usage of kernel stack, when the function call is not
in critical part.

This commit fixes the bug, including some minor code refactoring relevant
to variable names.

Fixes: 22d8de62f11b ("ALSA: control - add generic LED trigger module as the new control layer")
Signed-off-by: Takashi Sakamoto <o-takashi at sakamocchi.jp>
---
 sound/core/control_led.c | 68 ++++++++++++++++++++++++++--------------
 1 file changed, 44 insertions(+), 24 deletions(-)

diff --git a/sound/core/control_led.c b/sound/core/control_led.c
index b97f118cd54e..1be854a861f0 100644
--- a/sound/core/control_led.c
+++ b/sound/core/control_led.c
@@ -94,34 +94,35 @@ static struct snd_ctl_led *snd_ctl_led_get_by_access(unsigned int access)
 	return &snd_ctl_leds[group];
 }
 
-static int snd_ctl_led_get(struct snd_ctl_led_ctl *lctl)
+static int snd_ctl_led_get(struct snd_ctl_led_ctl *lctl, struct snd_ctl_elem_info *elem_info,
+			   struct snd_ctl_elem_value *elem_value)
 {
 	struct snd_kcontrol *kctl = lctl->kctl;
-	struct snd_ctl_elem_info info;
-	struct snd_ctl_elem_value value;
 	unsigned int i;
-	int result;
-
-	memset(&info, 0, sizeof(info));
-	info.id = kctl->id;
-	info.id.index += lctl->index_offset;
-	info.id.numid += lctl->index_offset;
-	result = kctl->info(kctl, &info);
-	if (result < 0)
+	int err;
+
+	memset(elem_info, 0, sizeof(*elem_info));
+	elem_info->id = kctl->id;
+	elem_info->id.index += lctl->index_offset;
+	elem_info->id.numid += lctl->index_offset;
+	err = kctl->info(kctl, elem_info);
+	if (err < 0)
 		return -1;
-	memset(&value, 0, sizeof(value));
-	value.id = info.id;
-	result = kctl->get(kctl, &value);
-	if (result < 0)
+
+	memset(elem_value, 0, sizeof(*elem_value));
+	elem_value->id = elem_info->id;
+	err = kctl->get(kctl, elem_value);
+	if (err < 0)
 		return -1;
-	if (info.type == SNDRV_CTL_ELEM_TYPE_BOOLEAN ||
-	    info.type == SNDRV_CTL_ELEM_TYPE_INTEGER) {
-		for (i = 0; i < info.count; i++)
-			if (value.value.integer.value[i] != info.value.integer.min)
+
+	if (elem_info->type == SNDRV_CTL_ELEM_TYPE_BOOLEAN ||
+	    elem_info->type == SNDRV_CTL_ELEM_TYPE_INTEGER) {
+		for (i = 0; i < elem_info->count; i++)
+			if (elem_value->value.integer.value[i] != elem_info->value.integer.min)
 				return 1;
-	} else if (info.type == SNDRV_CTL_ELEM_TYPE_INTEGER64) {
-		for (i = 0; i < info.count; i++)
-			if (value.value.integer64.value[i] != info.value.integer64.min)
+	} else if (elem_info->type == SNDRV_CTL_ELEM_TYPE_INTEGER64) {
+		for (i = 0; i < elem_info->count; i++)
+			if (elem_value->value.integer64.value[i] != elem_info->value.integer64.min)
 				return 1;
 	}
 	return 0;
@@ -132,6 +133,8 @@ static void snd_ctl_led_set_state(struct snd_card *card, unsigned int access,
 {
 	struct snd_ctl_led *led;
 	struct snd_ctl_led_ctl *lctl;
+	struct snd_ctl_elem_info *elem_info;
+	struct snd_ctl_elem_value *elem_value;
 	int route;
 	bool found;
 
@@ -146,10 +149,24 @@ static void snd_ctl_led_set_state(struct snd_card *card, unsigned int access,
 		mutex_unlock(&snd_ctl_led_mutex);
 		return;
 	}
+
+	elem_info = kmalloc(sizeof(*elem_info), GFP_KERNEL);
+	if (!elem_info) {
+		mutex_unlock(&snd_ctl_led_mutex);
+		return;
+	}
+
+	elem_value = kmalloc(sizeof(*elem_value), GFP_KERNEL);
+	if (!elem_value) {
+		kfree(elem_info);
+		mutex_unlock(&snd_ctl_led_mutex);
+		return;
+	}
+
 	list_for_each_entry(lctl, &led->controls, list) {
 		if (lctl->kctl == kctl && lctl->index_offset == ioff)
 			found = true;
-		UPDATE_ROUTE(route, snd_ctl_led_get(lctl));
+		UPDATE_ROUTE(route, snd_ctl_led_get(lctl, elem_info, elem_value));
 	}
 	if (!found && kctl && card) {
 		lctl = kzalloc(sizeof(*lctl), GFP_KERNEL);
@@ -159,10 +176,13 @@ static void snd_ctl_led_set_state(struct snd_card *card, unsigned int access,
 			lctl->kctl = kctl;
 			lctl->index_offset = ioff;
 			list_add(&lctl->list, &led->controls);
-			UPDATE_ROUTE(route, snd_ctl_led_get(lctl));
+			UPDATE_ROUTE(route, snd_ctl_led_get(lctl, elem_info, elem_value));
 		}
 		kfree(lctl);
 	}
+
+	kfree(elem_value);
+	kfree(elem_info);
 	mutex_unlock(&snd_ctl_led_mutex);
 	switch (led->mode) {
 	case MODE_OFF:		route = 1; break;
-- 
2.27.0