Add driver type detection

src/alsa.c

@@ -5,10 +5,15 @@
 #include <alsa/sound/uapi/tlv.h>
 
 #include "alsa.h"
+#include "scarlett2.h"
 #include "scarlett2-firmware.h"
+#include "scarlett2-ioctls.h"
 #include "stringhelper.h"
 #include "window-iface.h"
 
+#define MAJOR_HWDEP_VERSION_SCARLETT2 1
+#define MAJOR_HWDEP_VERSION_FCP 2
+
 #define MAX_TLV_RANGE_SIZE 1024
 
 // TLV type for channel labels
@@ -1067,7 +1072,81 @@ static void alsa_get_serial_number(struct alsa_card *card) {
   card->serial = strdup(serial);
 }
 
+// return true if the Firmware Version control exists and is writable
+// and locked (i.e. the FCP server is running)
+static int check_firmware_version_locked(struct alsa_card *card) {
+  snd_ctl_elem_id_t   *id;
+  snd_ctl_elem_info_t *info;
+
+  snd_ctl_elem_id_alloca(&id);
+  snd_ctl_elem_info_alloca(&info);
+
+  // look for the Firmware Version control
+  snd_ctl_elem_id_set_interface(id, SND_CTL_ELEM_IFACE_CARD);
+  snd_ctl_elem_id_set_name(id, "Firmware Version");
+  snd_ctl_elem_info_set_id(info, id);
+
+  // no Firmware Version control found
+  int err = snd_ctl_elem_info(card->handle, info);
+  if (err < 0)
+    return 0;
+
+  return snd_ctl_elem_info_is_writable(info) &&
+         snd_ctl_elem_info_is_locked(info);
+}
+
+// return the driver type for this card
+// DRIVER_TYPE_NONE: no driver
+// DRIVER_TYPE_HWDEP: Scarlett2 driver
+// DRIVER_TYPE_SOCKET: FCP driver
+// DRIVER_TYPE_SOCKET_UNINIT: FCP driver, but not initialised
+static int get_driver_type(struct alsa_card *card) {
+  snd_hwdep_t *hwdep;
+
+  int err = scarlett2_open_card(card->device, &hwdep);
+
+  // no hwdep for this card - driver type none
+  if (err == -ENOENT)
+    return DRIVER_TYPE_NONE;
+
+  // if we get EPERM, it's FCP but no server running
+  if (err == -EPERM)
+    return DRIVER_TYPE_SOCKET_UNINIT;
+
+  // if we get EBUSY, it's FCP
+  if (err == -EBUSY)
+    // fcp-server locks the Firmware Version control when it has
+    // finished starting up
+    return check_firmware_version_locked(card) ?
+      DRIVER_TYPE_SOCKET : DRIVER_TYPE_SOCKET_UNINIT;
+
+  // failed to open hwdep
+  if (err < 0)
+    return DRIVER_TYPE_NONE;
+
+  // we can open hwdep, so now check the protocol version
+  int ver = scarlett2_get_protocol_version(hwdep);
+  scarlett2_close(hwdep);
+
+  // failed to get protocol version
+  if (ver < 0)
+    return DRIVER_TYPE_NONE;
+
+  // hwdep protocol version 1.x.x is Scarlett2 driver
+  if (SCARLETT2_HWDEP_VERSION_MAJOR(ver) == MAJOR_HWDEP_VERSION_SCARLETT2)
+    return DRIVER_TYPE_HWDEP;
+
+  // hwdep protocol version 2.x.x is FCP driver (but not initialised,
+  // because we were able to open the hwdep)
+  if (SCARLETT2_HWDEP_VERSION_MAJOR(ver) == MAJOR_HWDEP_VERSION_FCP)
+    return DRIVER_TYPE_SOCKET_UNINIT;
+
+  return DRIVER_TYPE_NONE;
+}
+
 static void card_init(struct alsa_card *card) {
+  card->driver_type = get_driver_type(card);
+
   alsa_get_elem_list(card);
   alsa_set_lr_nums(card);
   alsa_get_routing_controls(card);

src/alsa.h

@@ -41,6 +41,19 @@ enum {
   HW_TYPE_COUNT
 };
 
+// driver types
+// NONE is 1st Gen or Scarlett2 before hwdep support was added
+// (no erase config or firmware update support)
+// HWDEP is the Scarlett2 driver after hwdep support was added
+// SOCKET is the FCP driver
+enum {
+  DRIVER_TYPE_NONE,
+  DRIVER_TYPE_HWDEP,
+  DRIVER_TYPE_SOCKET,
+  DRIVER_TYPE_SOCKET_UNINIT,
+  DRIVER_TYPE_COUNT
+};
+
 // names for the hardware types
 extern const char *hw_type_names[HW_TYPE_COUNT];
 
@@ -162,6 +175,7 @@ struct alsa_card {
   uint32_t            pid;
   char               *serial;
   char               *name;
+  int                 driver_type;
   char               *fcp_socket;
   int                 best_firmware_version;
   snd_ctl_t          *handle;