ALSA: hda - hdmi: Protect ELD buffer

Because the eld buffer can be simultaneously accessed from both
workqueue context (updating) and process context (kcontrol read),
we need to protect it with a mutex to guarantee consistency.

To avoid holding the mutex while reading the ELD info from the
codec, we introduce a temporary eld buffer.

Signed-off-by: David Henningsson <david.henningsson@canonical.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 7 insertions, 1 deletions

diff --git a/sound/pci/hda/hda_eld.c b/sound/pci/hda/hda_eld.c
index 16066d7763ec..7dd846380a50 100644
--- a/sound/pci/hda/hda_eld.c
+++ b/sound/pci/hda/hda_eld.c
@@ -500,10 +500,13 @@ static void hdmi_print_eld_info(struct snd_info_entry *entry,
 		[4 ... 7] = "reserved"
 	};
 
+	mutex_lock(&eld->lock);
 	snd_iprintf(buffer, "monitor_present\t\t%d\n", eld->monitor_present);
 	snd_iprintf(buffer, "eld_valid\t\t%d\n", eld->eld_valid);
-	if (!eld->eld_valid)
+	if (!eld->eld_valid) {
+		mutex_unlock(&eld->lock);
 		return;
+	}
 	snd_iprintf(buffer, "monitor_name\t\t%s\n", e->monitor_name);
 	snd_iprintf(buffer, "connection_type\t\t%s\n",
 				eld_connection_type_names[e->conn_type]);
@@ -525,6 +528,7 @@ static void hdmi_print_eld_info(struct snd_info_entry *entry,
 
 	for (i = 0; i < e->sad_count; i++)
 		hdmi_print_sad_info(i, e->sad + i, buffer);
+	mutex_unlock(&eld->lock);
 }
 
 static void hdmi_write_eld_info(struct snd_info_entry *entry,
@@ -538,6 +542,7 @@ static void hdmi_write_eld_info(struct snd_info_entry *entry,
 	long long val;
 	unsigned int n;
 
+	mutex_lock(&eld->lock);
 	while (!snd_info_get_line(buffer, line, sizeof(line))) {
 		if (sscanf(line, "%s %llx", name, &val) != 2)
 			continue;
@@ -589,6 +594,7 @@ static void hdmi_write_eld_info(struct snd_info_entry *entry,
 				e->sad_count = n + 1;
 		}
 	}
+	mutex_unlock(&eld->lock);
 }