[PATCH v2] ALSA: usb-audio: purge needless variable length array

[PATCH v2] ALSA: usb-audio: purge needless variable length array

[Takashi Sakamoto]

Variable length array is used in 'snd_us16x08_meter_get()', while there
is no need. It's better to purge it because variable length array has
overhead for stack handling.

This commit replaces the array with static length. Sparse generated below
warning.

sound/usb/mixer_us16x08.c:714:18: warning: Variable length array is used.

Fixes: d2bb390a2081 ("ALSA: usb-audio: Tascam US-16x08 DSP mixer quirk")
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
---
 sound/usb/mixer_us16x08.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/sound/usb/mixer_us16x08.c b/sound/usb/mixer_us16x08.c
index 7ac45ec..73a0b9a 100644
--- a/sound/usb/mixer_us16x08.c
+++ b/sound/usb/mixer_us16x08.c
@@ -711,7 +711,7 @@ static int snd_us16x08_meter_get(struct snd_kcontrol *kcontrol,
 	struct snd_usb_audio *chip = elem->head.mixer->chip;
 	struct snd_us16x08_meter_store *store = elem->private_data;
 	u8 meter_urb[64];
-	char tmp[max(sizeof(mix_init_msg1), sizeof(mix_init_msg2))];
+	char tmp[sizeof(mix_init_msg2)] = {0};
 
 	if (elem) {
 		store = (struct snd_us16x08_meter_store *) elem->private_data;
@@ -721,8 +721,8 @@ static int snd_us16x08_meter_get(struct snd_kcontrol *kcontrol,
 
 	switch (kcontrol->private_value) {
 	case 0:
-		memcpy(tmp, mix_init_msg1, sizeof(mix_init_msg1));
-		snd_us16x08_send_urb(chip, tmp, 4);
+		snd_us16x08_send_urb(chip, (char *)mix_init_msg1,
+				     sizeof(mix_init_msg1));
 		snd_us16x08_recv_urb(chip, meter_urb,
 			sizeof(meter_urb));
 		kcontrol->private_value++;
@@ -740,7 +740,7 @@ static int snd_us16x08_meter_get(struct snd_kcontrol *kcontrol,
 	case 3:
 		memcpy(tmp, mix_init_msg2, sizeof(mix_init_msg2));
 		tmp[2] = snd_get_meter_comp_index(store);
-		snd_us16x08_send_urb(chip, tmp, 10);
+		snd_us16x08_send_urb(chip, tmp, sizeof(mix_init_msg2));
 		snd_us16x08_recv_urb(chip, meter_urb,
 			sizeof(meter_urb));
 		kcontrol->private_value = 0;
-- 
2.9.3

Re: [PATCH v2] ALSA: usb-audio: purge needless variable length array

[Takashi Iwai]

On Tue, 21 Feb 2017 23:54:47 +0100,
Takashi Sakamoto wrote:
> 
> Variable length array is used in 'snd_us16x08_meter_get()', while there
> is no need. It's better to purge it because variable length array has
> overhead for stack handling.
> 
> This commit replaces the array with static length. Sparse generated below
> warning.
> 
> sound/usb/mixer_us16x08.c:714:18: warning: Variable length array is used.
> 
> Fixes: d2bb390a2081 ("ALSA: usb-audio: Tascam US-16x08 DSP mixer quirk")
> Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>

Applied, thanks.


Takashi