ALSA: fireworks: use managed-resource to maintain response buffer

ALSA fireworks driver allocates memory object to handle response from
target unit. The object is used to initiate transaction unique to
Fireworks board module. This can be released as managed-resource
of 'struct snd_card.card_dev'.

This commit uses managed-resource of the sound card device for this
purpose.
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/firewire/fireworks/fireworks.c

@@ -189,8 +189,6 @@ static void efw_free(struct snd_efw *efw)
 	snd_efw_stream_destroy_duplex(efw);
 	snd_efw_transaction_remove_instance(efw);
 
-	kfree(efw->resp_buf);
-
 	mutex_destroy(&efw->mutex);
 	fw_unit_put(efw->unit);
 }
@@ -247,8 +245,9 @@ do_registration(struct work_struct *work)
 	/* prepare response buffer */
 	snd_efw_resp_buf_size = clamp(snd_efw_resp_buf_size,
 				      SND_EFW_RESPONSE_MAXIMUM_BYTES, 4096U);
-	efw->resp_buf = kzalloc(snd_efw_resp_buf_size, GFP_KERNEL);
-	if (efw->resp_buf == NULL) {
+	efw->resp_buf = devm_kzalloc(&efw->card->card_dev,
+				     snd_efw_resp_buf_size, GFP_KERNEL);
+	if (!efw->resp_buf) {
 		err = -ENOMEM;
 		goto error;
 	}
@@ -300,8 +299,6 @@ do_registration(struct work_struct *work)
 	snd_efw_transaction_remove_instance(efw);
 	snd_efw_stream_destroy_duplex(efw);
 	snd_card_free(efw->card);
-	kfree(efw->resp_buf);
-	efw->resp_buf = NULL;
 	dev_info(&efw->unit->device,
 		 "Sound card registration failed: %d\n", err);
 }