[RFC][PATCH 3/3] ALSA: control: disable TLV data at initial state of user-defined element set

[Takashi Sakamoto <o-takashi@sakamocchi.jp>]

For user-defined element set, in its initial state, TLV data is not
registered. It's firstly available when any application register it by
an additional operation. However, in current implementation, it's available
in its initial state. As a result, applications get -ENXIO to read it.

This commit controls its readability to manage info flags properly. In an
initial state, elements don't have SND_CTL_ELEM_ACCESS_TLV_READ flag. Once
TLV write operation is executed, they get the flag.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
---
 sound/core/control.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/sound/core/control.c b/sound/core/control.c
index b8d2fa465a9d..f77b8ccbce34 100644
--- a/sound/core/control.c
+++ b/sound/core/control.c
@@ -1118,6 +1118,7 @@ static int replace_user_tlv(struct snd_kcontrol *kctl, unsigned int __user *buf,
 	struct user_element *ue = kctl->private_data;
 	unsigned int *container;
 	struct snd_ctl_elem_id id;
+	unsigned int mask = 0;
 	int i;
 	int change;
 
@@ -1136,13 +1137,21 @@ static int replace_user_tlv(struct snd_kcontrol *kctl, unsigned int __user *buf,
 		return 0;
 	}
 
+	if (ue->tlv_data == NULL) {
+		/* Now TLV data is available. */
+		for (i = 0; i < kctl->count; ++i)
+			kctl->vd[i].access |= SNDRV_CTL_ELEM_ACCESS_TLV_READ;
+		mask = SNDRV_CTL_EVENT_MASK_INFO;
+	}
+
 	kfree(ue->tlv_data);
 	ue->tlv_data = container;
 	ue->tlv_data_size = size;
 
+	mask |= SNDRV_CTL_EVENT_MASK_TLV;
 	for (i = 0; i < kctl->count; ++i) {
 		snd_ctl_build_ioff(&id, kctl, i);
-		snd_ctl_notify(ue->card, SNDRV_CTL_EVENT_MASK_TLV, &id);
+		snd_ctl_notify(ue->card, mask, &id);
 	}
 
 	return change;
@@ -1277,8 +1286,10 @@ static int snd_ctl_elem_add(struct snd_ctl_file *file,
 		access = SNDRV_CTL_ELEM_ACCESS_READWRITE;
 	access &= (SNDRV_CTL_ELEM_ACCESS_READWRITE |
 		   SNDRV_CTL_ELEM_ACCESS_INACTIVE |
-		   SNDRV_CTL_ELEM_ACCESS_TLV_READWRITE);
-	if (access & SNDRV_CTL_ELEM_ACCESS_TLV_READWRITE)
+		   SNDRV_CTL_ELEM_ACCESS_TLV_WRITE);
+
+	/* In initial state, nothing is available as TLV container. */
+	if (access & SNDRV_CTL_ELEM_ACCESS_TLV_WRITE)
 		access |= SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK;
 	access |= SNDRV_CTL_ELEM_ACCESS_USER;
 
@@ -1341,7 +1352,7 @@ static int snd_ctl_elem_add(struct snd_ctl_file *file,
 		kctl->get = snd_ctl_elem_user_get;
 	if (access & SNDRV_CTL_ELEM_ACCESS_WRITE)
 		kctl->put = snd_ctl_elem_user_put;
-	if (access & SNDRV_CTL_ELEM_ACCESS_TLV_READWRITE)
+	if (access & SNDRV_CTL_ELEM_ACCESS_TLV_WRITE)
 		kctl->tlv.c = snd_ctl_elem_user_tlv;
 
 	/* This function manage to free the instance on failure. */
-- 
2.11.0