Rework hardware probing and RTL-SDR helper startup

The lazy startup of the separate helper program for the RTL-SDR
backend on playback start was incorrect with respect to the expected
behavior the frequency setting verbs.  This was not visible during
usage by the radio application, but was triggering failures in
several tests in the pyagl binding wrapper test suite.  To facilitate
starting the helper during backend initialization, the probing part
of the backend "init" has been split into a separate "probe" function,
and all backends have been updated to reflect this change.  Logic has
been added to enforce that "init" is only called after "probe" has
succeeded for a backend, and a comment has been added to radio_impl.h
to document this intended behavior.

Bug-AGL: SPEC-3717

Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Change-Id: Ic37331a92bae7cc01ee448e69894fa5f49d08a74

1 files changed, 89 insertions, 72 deletions

diff --git a/binding/radio_impl_rtlsdr.c b/binding/radio_impl_rtlsdr.c
index 62ec623..2087d10 100644
--- a/binding/radio_impl_rtlsdr.c
+++ b/binding/radio_impl_rtlsdr.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2017,2018 Konsulko Group
+ * Copyright (C) 2017,2018,2020 Konsulko Group
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -57,6 +57,7 @@ static int helper_in;
 static int helper_out;
 static pthread_mutex_t helper_mutex = PTHREAD_MUTEX_INITIALIZER;
 static bool present;
+static bool initialized;
 static bool active;
 static bool scanning;
 static uint32_t current_frequency;
@@ -128,16 +129,89 @@ static pid_t popen2(char *command, int *in_fd, int *out_fd)
 	return pid;
 }
 
-static int rtlsdr_init(void)
+static int rtlsdr_probe(void)
 {
-	GKeyFile *conf_file;
-	char *value_str;
 	char *rootdir;
 	char *helper_path;
 
 	if(present)
 		return 0;
 
+	rootdir = getenv("AFM_APP_INSTALL_DIR");
+	if(!rootdir)
+		return -1;
+
+	// Run helper to detect adapter
+	helper_path = malloc(HELPER_MAX);
+	if(!helper_path)
+		return -ENOMEM;
+	if(snprintf(helper_path, HELPER_MAX, "%s/bin/%s --detect", rootdir, HELPER_NAME) == HELPER_MAX) {
+		AFB_API_ERROR(afbBindingV3root, "Could not create command for \"%s --detect\"", HELPER_NAME);
+		return -EINVAL;
+	}
+	if(system(helper_path) != 0) {
+		free(helper_path);
+		return -1;
+	}
+
+	present = true;
+	return 0;
+}
+
+static int rtlsdr_start_helper(void)
+{
+	char *rootdir;
+	char *helper_path;
+	static bool helper_started = false;
+
+	if(!present || initialized)
+		return -1;
+
+	if(helper_started)
+		return 0;
+
+	rootdir = getenv("AFM_APP_INSTALL_DIR");
+	if(!rootdir)
+		return -1;
+
+	if(helper_output) {
+		// Indicate desired output to helper
+		AFB_API_INFO(afbBindingV3root, "Setting RADIO_OUTPUT=%s", helper_output);
+		setenv("RADIO_OUTPUT", helper_output, 1);
+	}
+
+	// Run helper
+	helper_path = malloc(HELPER_MAX);
+	if(!helper_path)
+		return -ENOMEM;
+	if(snprintf(helper_path, PATH_MAX, "%s/bin/%s", rootdir, HELPER_NAME) == PATH_MAX) {
+		AFB_API_ERROR(afbBindingV3root, "Could not create path to %s", HELPER_NAME);
+		return -EINVAL;
+	}
+	helper_pid = popen2(helper_path, &helper_out, &helper_in);
+	if(helper_pid < 0) {
+		AFB_API_ERROR(afbBindingV3root, "Could not run %s!", HELPER_NAME);
+		return -1;
+	}
+	AFB_API_DEBUG(afbBindingV3root, "%s started", HELPER_NAME);
+	helper_started = true;
+	free(helper_path);
+
+	return 0;
+}
+
+static int rtlsdr_init(void)
+{
+	GKeyFile *conf_file;
+	char *value_str;
+	int rc;
+
+	if(!present)
+		return -1;
+
+	if(initialized)
+		return 0;
+
 	// Load settings from configuration file if it exists
 	conf_file = g_key_file_new();
 	if(conf_file &&
@@ -168,25 +242,12 @@ static int rtlsdr_init(void)
 
 	// Start off with minimum bandplan frequency
 	current_frequency = rtlsdr_get_min_frequency(BAND_FM);
-
-	rootdir = getenv("AFM_APP_INSTALL_DIR");
-	if(!rootdir)
-		return -1;
-
-	// Run helper to detect adapter
-	helper_path = malloc(HELPER_MAX);
-	if(!helper_path)
-		return -ENOMEM;
-	if(snprintf(helper_path, HELPER_MAX, "%s/bin/%s --detect", rootdir, HELPER_NAME) == HELPER_MAX) {
-		AFB_API_ERROR(afbBindingV3root, "Could not create command for \"%s --detect\"", HELPER_NAME);
-		return -EINVAL;
-	}
-	if(system(helper_path) != 0) {
-		free(helper_path);
-		return -1;
+	rc = rtlsdr_start_helper();
+	if(rc != 0) {
+		return rc;
 	}
 
-	present = true;
+	initialized = true;
 	rtlsdr_set_frequency(current_frequency);
 
 	return 0;
@@ -212,7 +273,7 @@ static void rtlsdr_set_frequency(uint32_t frequency)
 	ssize_t rc;
 	uint32_t n;
 
-	if(!present)
+	if(!initialized)
 		return;
 
 	if(frequency < known_fm_band_plans[bandplan].min ||
@@ -298,62 +359,17 @@ static uint32_t rtlsdr_get_frequency_step(radio_band_t band)
 	return ret;
 }
 
-static int rtlsdr_start_helper(void)
-{
-	char *rootdir;
-	char *helper_path;
-	static bool helper_started = false;
-
-	if(!present)
-		return -1;
-
-	if(helper_started)
-		return 0;
-
-	rootdir = getenv("AFM_APP_INSTALL_DIR");
-	if(!rootdir)
-		return -1;
-
-	if(helper_output) {
-		// Indicate desired output to helper
-		AFB_API_INFO(afbBindingV3root, "Setting RADIO_OUTPUT=%s", helper_output);
-		setenv("RADIO_OUTPUT", helper_output, 1);
-	}
-
-	// Run helper
-	helper_path = malloc(HELPER_MAX);
-	if(!helper_path)
-		return -ENOMEM;
-	if(snprintf(helper_path, PATH_MAX, "%s/bin/%s", rootdir, HELPER_NAME) == PATH_MAX) {
-		AFB_API_ERROR(afbBindingV3root, "Could not create path to %s", HELPER_NAME);
-		return -EINVAL;
-	}
-	helper_pid = popen2(helper_path, &helper_out, &helper_in);
-	if(helper_pid < 0) {
-		AFB_API_ERROR(afbBindingV3root, "Could not run %s!", HELPER_NAME);
-		return -1;
-	}
-	AFB_API_DEBUG(afbBindingV3root, "%s started", HELPER_NAME);
-	helper_started = true;
-	free(helper_path);
-
-	return 0;
-}
-
 static void rtlsdr_start(void)
 {
-	if(!present)
-		return;
+	ssize_t rc;
+	char cmd[HELPER_CMD_MAXLEN];
 
-	if(active)
+	if(!initialized)
 		return;
 
-	if(rtlsdr_start_helper() < 0)
+	if(active)
 		return;
 
-	ssize_t rc;
-	char cmd[HELPER_CMD_MAXLEN];
-
 	snprintf(cmd, sizeof(cmd), "START\n");
 	pthread_mutex_lock(&helper_mutex);
 	rc = write(helper_in, cmd, strlen(cmd));
@@ -368,7 +384,7 @@ static void rtlsdr_start(void)
 static void rtlsdr_stop(void)
 {
 	ssize_t rc;
-	if(!present)
+	if(!initialized)
 		return;
 
 	if (!active)
@@ -470,6 +486,7 @@ static void rtlsdr_set_stereo_mode(radio_stereo_mode_t mode)
 
 radio_impl_ops_t rtlsdr_impl_ops = {
 	.name = "RTL-SDR USB adapter",
+	.probe = rtlsdr_probe,
 	.init = rtlsdr_init,
 	.set_output = rtlsdr_set_output,
 	.get_frequency = rtlsdr_get_frequency,