dsprpcd: Add help functionality

Add -h/--help support to display daemon usage, functionality,
DSP-specific shell file naming conventions, and command-line
options with appropriate examples for each DSP subsystem.

Signed-off-by: Vinayak Katoch <vkatoch@qti.qualcomm.com>

Author: quic-vkatoch

src/dsprpcd.c

@@ -34,6 +34,62 @@
 
 typedef int (*dsp_default_listener_start_t)(int argc, char *argv[]);
 
+/**
+ * Prints help information about the daemon.
+ */
+static void print_help(const char *program_name, const char *dsp_name) {
+  printf("Usage: %s [OPTIONS]\n\n", program_name);
+  printf("Description:\n");
+  printf("  %s is a daemon that establishes a connection to the guest PD\n", program_name);
+  printf("  (Process Domain) on the %s, functioning similarly to the root\n", dsp_name);
+  printf("  process in Linux.\n\n");
+  printf("Functionality:\n");
+  printf("  - DSP Process Exception Logs:\n");
+  printf("    Facilitates transfer of %s process exception logs to the HLOS\n", dsp_name);
+  printf("    (High-Level Operating System) logging infrastructure for effective\n");
+  printf("    monitoring and debugging.\n\n");
+  printf("  - Fastrpc Shell File Execution:\n");
+  printf("    Enables execution of fastrpc shell file (executable file that runs\n");
+  printf("    as a process on the %s). When applications offload tasks to the %s\n", dsp_name, dsp_name);
+  printf("    but cannot access shell file directly, the daemon reads the shell\n");
+  printf("    file from the HLOS file system and creates the necessary process on\n");
+  printf("    the %s.\n\n", dsp_name);
+  printf("    Shell file naming format:\n");
+#ifdef USE_ADSP
+  printf("      - Signed: fastrpc_shell_<domain_id> (ADSP supports signed only)\n\n");
+#elif defined(USE_SDSP)
+  printf("      - Signed: fastrpc_shell_<domain_id> (SDSP supports signed only)\n\n");
+#elif defined(USE_CDSP)
+  printf("      - Signed: fastrpc_shell_<domain_id>\n");
+  printf("      - Unsigned: fastrpc_shell_unsigned_<domain_id>\n\n");
+#elif defined(USE_GDSP)
+  printf("      - Signed: fastrpc_shell_<domain_id>\n");
+  printf("      - Unsigned: fastrpc_shell_unsigned_<domain_id>\n\n");
+#endif
+  printf("Options:\n");
+  printf("  -h, --help              Display this help message and exit\n");
+  printf("  <pd_name> <domain>      Start daemon for specific PD and domain\n");
+#ifdef USE_ADSP
+  printf("                          Example: %s audiopd adsp\n", program_name);
+#elif defined(USE_SDSP)
+  printf("                          Example: %s rootpd sdsp\n", program_name);
+#elif defined(USE_CDSP)
+  printf("                          Example: %s rootpd cdsp (or cdsp1)\n", program_name);
+#elif defined(USE_GDSP)
+  printf("                          Example: %s rootpd gdsp0 (or gdsp1)\n", program_name);
+#endif
+  printf("  <pd_name>               Start daemon for specific PD (uses default domain)\n");
+#ifdef USE_ADSP
+  printf("                          Example: %s audiopd\n", program_name);
+#else
+  printf("                          Example: %s rootpd\n", program_name);
+#endif
+  printf("  (no arguments)          Start daemon for root PD (default/guest OS)\n\n");
+  printf("Notes:\n");
+  printf("  - This daemon runs continuously and automatically restarts on errors\n");
+  printf("  - It exits only when the fastRPC device node is not accessible\n\n");
+}
+
 // Result struct for dlopen.
 struct dlopen_result {
   void *handle;
@@ -93,6 +149,15 @@ int main(int argc, char *argv[]) {
   #else
     goto bail;
   #endif
+
+  // Check for help flag
+  if (argc > 1) {
+    if (strcmp(argv[1], "-h") == 0 || strcmp(argv[1], "--help") == 0) {
+      print_help(argv[0], dsp_name);
+      return 0;
+    }
+  }
+
   VERIFY_EPRINTF("%s daemon starting", dsp_name);
 
   while (1) {