From 809f515013da012b5a370095cbbf7cd0d2b89f4a Mon Sep 17 00:00:00 2001
From: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Date: Sun, 21 Jun 2020 21:19:36 +0900
Subject: [PATCH] ctl: add an API to retrieve current version of protocol in
 control interface

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
---
 src/ctl/alsactl.map |  1 +
 src/ctl/card.c      | 43 +++++++++++++++++++++++++++++++++++++++++++
 src/ctl/card.h      |  4 ++++
 tests/alsactl-card  |  1 +
 4 files changed, 49 insertions(+)

diff --git a/src/ctl/alsactl.map b/src/ctl/alsactl.map
index 396eafd..e5989f5 100644
--- a/src/ctl/alsactl.map
+++ b/src/ctl/alsactl.map
@@ -14,6 +14,7 @@ ALSA_GOBJECT_0_0_0 {
     "alsactl_card_get_type";
     "alsactl_card_new";
     "alsactl_card_open";
+    "alsactl_card_get_protocol_version";
     "alsactl_card_get_info";
     "alsactl_card_get_elem_id_list";
     "alsactl_card_lock_elem";
diff --git a/src/ctl/card.c b/src/ctl/card.c
index 5324da1..0a49fbb 100644
--- a/src/ctl/card.c
+++ b/src/ctl/card.c
@@ -26,6 +26,7 @@ struct _ALSACtlCardPrivate {
     int fd;
     char *devnode;
     gint subscribers;
+    guint16 proto_ver_triplet[3];
 };
 G_DEFINE_TYPE_WITH_PRIVATE(ALSACtlCard, alsactl_card, G_TYPE_OBJECT)
 
@@ -179,6 +180,7 @@ void alsactl_card_open(ALSACtlCard *self, guint card_id, gint open_flag,
 {
     ALSACtlCardPrivate *priv;
     char *devnode;
+    int proto_ver;
 
     g_return_if_fail(ALSACTL_IS_CARD(self));
     priv = alsactl_card_get_instance_private(self);
@@ -195,7 +197,48 @@ void alsactl_card_open(ALSACtlCard *self, guint card_id, gint open_flag,
         return;
     }
 
+    // Remember the version of protocol currently used.
+    if (ioctl(priv->fd, SNDRV_CTL_IOCTL_PVERSION, &proto_ver) < 0) {
+        generate_error(error, errno);
+        close(priv->fd);
+        priv->fd = -1;
+        g_free(devnode);
+        return;
+    }
+
     priv->devnode = devnode;
+    priv->proto_ver_triplet[0] = SNDRV_PROTOCOL_MAJOR(proto_ver);
+    priv->proto_ver_triplet[1] = SNDRV_PROTOCOL_MINOR(proto_ver);
+    priv->proto_ver_triplet[2] = SNDRV_PROTOCOL_MICRO(proto_ver);
+}
+
+/**
+ * alsactl_card_get_protocol_version:
+ * @self: A #ALSACtlCard.
+ * @proto_ver_triplet: (array fixed-size=3)(out)(transfer none): The version of
+ *                     protocol currently used.
+ * @error: A #GError.
+ *
+ * Get the version of control protocol currently used. The version is
+ * represented as the array with three elements; major, minor, and micro version
+ * in the order. The length of major version is 16 bit, the length of minor
+ * and micro version is 8 bit each.
+ */
+void alsactl_card_get_protocol_version(ALSACtlCard *self,
+                                       const guint16 *proto_ver_triplet[3],
+                                       GError **error)
+{
+    ALSACtlCardPrivate *priv;
+
+    g_return_if_fail(ALSACTL_IS_CARD(self));
+    priv = alsactl_card_get_instance_private(self);
+
+    if (priv->fd < 0) {
+        generate_error(error, ENXIO);
+        return;
+    }
+
+    *proto_ver_triplet = (const guint16 *)priv->proto_ver_triplet;
 }
 
 /**
diff --git a/src/ctl/card.h b/src/ctl/card.h
index 08694d3..d26b464 100644
--- a/src/ctl/card.h
+++ b/src/ctl/card.h
@@ -79,6 +79,10 @@ ALSACtlCard *alsactl_card_new();
 void alsactl_card_open(ALSACtlCard *self, guint card_id, gint open_flag,
                        GError **error);
 
+void alsactl_card_get_protocol_version(ALSACtlCard *self,
+                                       const guint16 *proto_ver_triplet[3],
+                                       GError **error);
+
 void alsactl_card_get_info(ALSACtlCard *self, ALSACtlCardInfo **card_info,
                            GError **error);
 
diff --git a/tests/alsactl-card b/tests/alsactl-card
index e1e089c..e9d7702 100644
--- a/tests/alsactl-card
+++ b/tests/alsactl-card
@@ -17,6 +17,7 @@ props = (
 methods = (
     'new',
     'open',
+    'get_protocol_version',
     'get_info',
     'get_elem_id_list',
     'lock_elem',
-- 
2.47.3