From a7d2718aa4a887025e5134d55882d0c5cc4b6d5c Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Tue, 29 Nov 2022 17:34:45 +0100
Subject: [PATCH] ALSA: use dedicated device reservation for probing

It can happen that the main AlsaAudioBackend::_device_reservation
is still busy while I/O devices are set. In this case a
dedicated AlsaDeviceReservation needs to be used which can fail
silently.

A common example is disconnecting a USB device while it is in
use. The Halted signal can show the session dialog, which calls
set_input_device_name before the device reservation of the
unplugged device terminated.
---
 libs/backends/alsa/alsa_audiobackend.cc | 16 ++++++++++------
 libs/backends/alsa/alsa_audiobackend.h  |  2 +-
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/libs/backends/alsa/alsa_audiobackend.cc b/libs/backends/alsa/alsa_audiobackend.cc
index 5fbfd9204c..9855f953ce 100644
--- a/libs/backends/alsa/alsa_audiobackend.cc
+++ b/libs/backends/alsa/alsa_audiobackend.cc
@@ -346,10 +346,9 @@ AlsaAudioBackend::set_input_device_name (const std::string& d)
 		_input_audio_device_info.valid = false;
 		return 1;
 	}
-	_device_reservation.acquire_device (alsa_device.c_str ());
+	AlsaDeviceReservation adr (alsa_device.c_str ());
 	/* device will be busy once used, hence cache the parameters */
 	/* return */ get_alsa_device_parameters (alsa_device.c_str (), false, &_input_audio_device_info);
-	_device_reservation.release_device ();
 	return 0;
 }
 
@@ -380,6 +379,7 @@ AlsaAudioBackend::set_output_device_name (const std::string& d)
 		_output_audio_device_info.valid = false;
 		return 1;
 	}
+	AlsaDeviceReservation adr (alsa_device.c_str ());
 	/* return */ get_alsa_device_parameters (alsa_device.c_str (), true, &_output_audio_device_info);
 	return 0;
 }
@@ -2427,7 +2427,7 @@ AlsaDeviceReservation::AlsaDeviceReservation ()
 AlsaDeviceReservation::AlsaDeviceReservation (const char* device_name)
 	: _device_reservation (0)
 {
-	acquire_device (device_name);
+	acquire_device (device_name, true);
 }
 
 AlsaDeviceReservation::~AlsaDeviceReservation ()
@@ -2436,7 +2436,7 @@ AlsaDeviceReservation::~AlsaDeviceReservation ()
 }
 
 bool
-AlsaDeviceReservation::acquire_device (const char* device_name)
+AlsaDeviceReservation::acquire_device (const char* device_name, bool silent)
 {
 	int device_number = card_to_num (device_name);
 	if (device_number < 0) {
@@ -2470,7 +2470,9 @@ AlsaDeviceReservation::acquire_device (const char* device_name)
 	_device_reservation->Terminated.connect_same_thread (_reservation_connection, boost::bind (&AlsaDeviceReservation::release_device, this));
 
 	if (_device_reservation->start (SystemExec::ShareWithParent)) {
-		PBD::warning << _("AlsaAudioBackend: Device Request failed.") << endmsg;
+		if (!silent) {
+			PBD::warning << _("AlsaAudioBackend: Device Request failed.") << endmsg;
+		}
 		release_device ();
 		return false;
 	}
@@ -2482,7 +2484,9 @@ AlsaDeviceReservation::acquire_device (const char* device_name)
 	}
 
 	if (timeout == 0 || !_reservation_succeeded) {
-		PBD::warning << _("AlsaAudioBackend: Device Reservation failed.") << endmsg;
+		if (!silent) {
+			PBD::warning << _("AlsaAudioBackend: Device Reservation failed.") << endmsg;
+		}
 		release_device ();
 		return false;
 	}
diff --git a/libs/backends/alsa/alsa_audiobackend.h b/libs/backends/alsa/alsa_audiobackend.h
index dbec753dd3..7385d19071 100644
--- a/libs/backends/alsa/alsa_audiobackend.h
+++ b/libs/backends/alsa/alsa_audiobackend.h
@@ -106,7 +106,7 @@ class AlsaDeviceReservation
 		AlsaDeviceReservation (const char* device_name);
 		~AlsaDeviceReservation ();
 
-		bool acquire_device (const char* device_name);
+		bool acquire_device (const char* device_name, bool silent = false);
 		void release_device ();
 
 	private: