ALSA: 6fire: fix DMA issues with URB transfer_buffer usage

Patch fixes 6fire not to use stack as URB transfer_buffer. URB buffers need to
be DMA-able, which stack is not. Furthermore, transfer_buffer should not be
allocated as part of larger device structure because DMA coherency issues and
patch fixes this issue too.

Cc: [e-mail]
Signed-off-by: Jussi Kivilinna <[e-mail]>
Tested-by: Torsten Schenk <[e-mail]>
Signed-off-by: Takashi Iwai <[e-mail]>

sound/usb/6fire/comm.c

···
 static int usb6fire_comm_write8(struct comm_runtime *rt, u8 request,
 		u8 reg, u8 value)
 {
-	u8 buffer[13]; /* 13: maximum length of message */
+	u8 *buffer;
+	int ret;
+
+	/* 13: maximum length of message */
+	buffer = kmalloc(13, GFP_KERNEL);
+	if (!buffer)
+		return -ENOMEM;
 
 	usb6fire_comm_init_buffer(buffer, 0x00, request, reg, value, 0x00);
-	return usb6fire_comm_send_buffer(buffer, rt->chip->dev);
+	ret = usb6fire_comm_send_buffer(buffer, rt->chip->dev);
+
+	kfree(buffer);
+	return ret;
 }
 
 static int usb6fire_comm_write16(struct comm_runtime *rt, u8 request,
 		u8 reg, u8 vl, u8 vh)
 {
-	u8 buffer[13]; /* 13: maximum length of message */
+	u8 *buffer;
+	int ret;
+
+	/* 13: maximum length of message */
+	buffer = kmalloc(13, GFP_KERNEL);
+	if (!buffer)
+		return -ENOMEM;
 
 	usb6fire_comm_init_buffer(buffer, 0x00, request, reg, vl, vh);
-	return usb6fire_comm_send_buffer(buffer, rt->chip->dev);
+	ret = usb6fire_comm_send_buffer(buffer, rt->chip->dev);
+
+	kfree(buffer);
+	return ret;
 }
 
 int usb6fire_comm_init(struct sfire_chip *chip)
···
 
 	if (!rt)
 		return -ENOMEM;
+
+	rt->receiver_buffer = kzalloc(COMM_RECEIVER_BUFSIZE, GFP_KERNEL);
+	if (!rt->receiver_buffer) {
+		kfree(rt);
+		return -ENOMEM;
+	}
 
 	urb = &rt->receiver;
 	rt->serial = 1;
···
 	urb->interval = 1;
 	ret = usb_submit_urb(urb, GFP_KERNEL);
 	if (ret < 0) {
+		kfree(rt->receiver_buffer);
 		kfree(rt);
 		snd_printk(KERN_ERR PREFIX "cannot create comm data receiver.");
 		return ret;
···
 
 void usb6fire_comm_destroy(struct sfire_chip *chip)
 {
-	kfree(chip->comm);
+	struct comm_runtime *rt = chip->comm;
+
+	kfree(rt->receiver_buffer);
+	kfree(rt);
 	chip->comm = NULL;
 }

sound/usb/6fire/comm.h

···
 	struct sfire_chip *chip;
 
 	struct urb receiver;
-	u8 receiver_buffer[COMM_RECEIVER_BUFSIZE];
+	u8 *receiver_buffer;
 
 	u8 serial; /* urb serial */