Re: [MOD] STR #4128: libusb-based USB backend: Further fixes

--- backend/usb-libusb.c	2012-06-22 11:53:36.103353715 +0200
+++ backend/usb-libusb.c	2012-06-22 11:52:50.723163432 +0200
@@ -22,6 +22,8 @@
  *   make_device_uri()	  - Create a device URI for a USB printer.
  *   open_device()	  - Open a connection to the USB printer.
  *   print_cb() 	  - Find a USB printer for printing.
+ *   printer_class_soft_reset()' - Do the soft reset request specific to
+ *                          printers
  *   read_thread()	  - Thread to read the backchannel data on.
  *   sidechannel_thread() - Handle side-channel requests.
  *   soft_reset()	  - Send a soft reset to the device.
@@ -60,12 +62,13 @@
 {
   struct libusb_device	*device;	/* Device info */
   int			conf,		/* Configuration */
+			origconf,	/* Original configuration */
 			iface,		/* Interface */
 			altset,		/* Alternate setting */
 			write_endp,	/* Write endpoint */
-                        read_endp,	/* Read endpoint */
+			read_endp,	/* Read endpoint */
 			protocol,	/* Protocol: 1 = Uni-di, 2 = Bi-di. */
-                        usblp_attached; /* Is the "usblp" kernel module
+			usblp_attached;	/* Is the "usblp" kernel module
 					   attached? */
   struct libusb_device_handle *handle;	/* Open handle to device */
 } usb_printer_t;
@@ -124,6 +127,7 @@
 static int		open_device(usb_printer_t *printer, int verbose);
 static int		print_cb(usb_printer_t *printer, const char *device_uri,
 			         const char *device_id, const void *data);
+static int		printer_class_soft_reset(usb_printer_t *printer);
 static void		*read_thread(void *reference);
 static void		*sidechannel_thread(void *reference);
 static void		soft_reset(void);
@@ -163,7 +167,8 @@
 		iostatus;		/* Current IO status */
   pthread_t	read_thread_id,		/* Read thread */
 		sidechannel_thread_id;	/* Side-channel thread */
-  int		have_sidechannel = 0;	/* Was the side-channel thread started? */
+  int		have_sidechannel = 0,	/* Was the side-channel thread started? */
+		have_backchannel = 0;   /* Do we have a back channel? */
   struct stat   sidechannel_info;	/* Side-channel file descriptor info */
   unsigned char	print_buffer[8192],	/* Print data buffer */
 		*print_ptr;		/* Pointer into print data buffer */
@@ -172,6 +177,9 @@
   struct timeval *timeout,		/* Timeout pointer */
 		tv;			/* Time value */
   struct timespec cond_timeout;		/* pthread condition timeout */
+  int		num_opts;		/* Number of options */
+  cups_option_t	*opts;			/* Options */
+  const char	*val;			/* Option value */
 
 
  /*
@@ -187,6 +195,7 @@
   * Connect to the printer...
   */
 
+  fprintf(stderr, "DEBUG: Printing on printer with URI: %s\n", uri);
   while ((g.printer = find_device(print_cb, uri)) == NULL)
   {
     _cupsLangPrintFilter(stderr, "INFO",
@@ -240,24 +249,47 @@
   }
 
  /*
-  * Get the read thread going...
+  * Debug mode: If option "usb-unidir" is given, always deactivate
+  * backchannel
   */
 
-  g.read_thread_stop = 0;
-  g.read_thread_done = 0;
+  num_opts = cupsParseOptions(argv[5], 0, &opts);
+  val = cupsGetOption("usb-unidir", num_opts, opts);
+  if (val && strcasecmp(val, "no") && strcasecmp(val, "off") &&
+      strcasecmp(val, "false"))
+  {
+    g.printer->read_endp = -1;
+    fprintf(stderr, "DEBUG: Forced uni-directional communication "
+	    "via \"usb-unidir\" option.\n");
+  }
 
-  pthread_cond_init(&g.read_thread_cond, NULL);
-  pthread_mutex_init(&g.read_thread_mutex, NULL);
+ /*
+  * Get the read thread going...
+  */
 
-  if (pthread_create(&read_thread_id, NULL, read_thread, NULL))
+  if (g.printer->read_endp != -1)
   {
-    fprintf(stderr, "DEBUG: Fatal USB error.\n");
-    _cupsLangPrintFilter(stderr, "ERROR",
-                         _("There was an unrecoverable USB error."));
-    fputs("DEBUG: Couldn't create read thread.\n", stderr);
-    close_device(g.printer);
-    return (CUPS_BACKEND_STOP);
+    have_backchannel = 1;
+
+    g.read_thread_stop = 0;
+    g.read_thread_done = 0;
+
+    pthread_cond_init(&g.read_thread_cond, NULL);
+    pthread_mutex_init(&g.read_thread_mutex, NULL);
+
+    if (pthread_create(&read_thread_id, NULL, read_thread, NULL))
+    {
+      fprintf(stderr, "DEBUG: Fatal USB error.\n");
+      _cupsLangPrintFilter(stderr, "ERROR",
+			   _("There was an unrecoverable USB error."));
+      fputs("DEBUG: Couldn't create read thread.\n", stderr);
+      close_device(g.printer);
+      return (CUPS_BACKEND_STOP);
+    }
   }
+  else
+    fprintf(stderr, "DEBUG: Uni-directional device/mode, back channel "
+	    "deactivated.\n");
 
  /*
   * The main thread sends the print file...
@@ -515,50 +547,54 @@
   * Signal the read thread to exit then wait 7 seconds for it to complete...
   */
 
-  g.read_thread_stop = 1;
-
-  pthread_mutex_lock(&g.read_thread_mutex);
-
-  if (!g.read_thread_done)
+  if (have_backchannel)
   {
-    fputs("DEBUG: Waiting for read thread to exit...\n", stderr);
-
-    gettimeofday(&tv, NULL);
-    cond_timeout.tv_sec  = tv.tv_sec + WAIT_EOF_DELAY;
-    cond_timeout.tv_nsec = tv.tv_usec * 1000;
+    g.read_thread_stop = 1;
 
-    while (!g.read_thread_done)
-    {
-      if (pthread_cond_timedwait(&g.read_thread_cond, &g.read_thread_mutex,
-				 &cond_timeout) != 0)
-	break;
-    }
+    pthread_mutex_lock(&g.read_thread_mutex);
 
-   /*
-    * If it didn't exit abort the pending read and wait an additional second...
-    */
-  
     if (!g.read_thread_done)
     {
-      fputs("DEBUG: Read thread still active, aborting the pending read...\n", 
-	    stderr);
-
-      g.wait_eof = 0;
+      fputs("DEBUG: Waiting for read thread to exit...\n", stderr);
 
       gettimeofday(&tv, NULL);
-      cond_timeout.tv_sec  = tv.tv_sec + 1;
+      cond_timeout.tv_sec  = tv.tv_sec + WAIT_EOF_DELAY;
       cond_timeout.tv_nsec = tv.tv_usec * 1000;
-  
+
       while (!g.read_thread_done)
       {
 	if (pthread_cond_timedwait(&g.read_thread_cond, &g.read_thread_mutex,
 				   &cond_timeout) != 0)
 	  break;
       }
+
+      /*
+       * If it didn't exit abort the pending read and wait an additional
+       * second...
+       */
+  
+      if (!g.read_thread_done)
+      {
+	fputs("DEBUG: Read thread still active, aborting the pending read...\n", 
+	      stderr);
+
+	g.wait_eof = 0;
+
+	gettimeofday(&tv, NULL);
+	cond_timeout.tv_sec  = tv.tv_sec + 1;
+	cond_timeout.tv_nsec = tv.tv_usec * 1000;
+  
+	while (!g.read_thread_done)
+	{
+	  if (pthread_cond_timedwait(&g.read_thread_cond, &g.read_thread_mutex,
+				     &cond_timeout) != 0)
+	    break;
+	}
+      }
     }
-  }
 
-  pthread_mutex_unlock(&g.read_thread_mutex);
+    pthread_mutex_unlock(&g.read_thread_mutex);
+  }
 
   if (print_fd)
     close(print_fd);
@@ -601,24 +637,51 @@
     */
 
     int errcode;			/* Return value of libusb function */
-    int number;				/* Interface number */
+    int number1,			/* Interface number */
+	number2;			/* Configuration number */
 
     errcode = 
       libusb_get_config_descriptor (printer->device, printer->conf, &confptr);
     if (errcode >= 0)
     {
-      number = confptr->interface[printer->iface].
+      number1 = confptr->interface[printer->iface].
 	altsetting[printer->altset].bInterfaceNumber;
-      libusb_release_interface(printer->handle, number);
-      if (number != 0)
-	libusb_release_interface(printer->handle, 0);
+      libusb_release_interface(printer->handle, number1);
+
+      number2 = confptr->bConfigurationValue;
+
+      libusb_free_config_descriptor(confptr);
+
+     /*
+      * If we have changed the configuration, restore the old one
+      */
+      if (printer->origconf != number2)
+	fprintf(stderr, "DEBUG: Restoring USB device configuration: %d -> %d\n", 
+		number2, printer->origconf);
+	if ((errcode = libusb_set_configuration(printer->handle,
+						printer->origconf)) < 0)
+	{
+	  if (errcode != LIBUSB_ERROR_BUSY)
+	  {
+	    errcode =
+	      libusb_get_device_descriptor (printer->device, &devdesc);
+	    if (errcode < 0)
+	      fprintf(stderr,
+		      "DEBUG: Failed to set configuration %d\n",
+		      printer->origconf);
+	    else
+	      fprintf(stderr,
+		      "DEBUG: Failed to set configuration %d for %04x:%04x\n",
+		      printer->origconf, devdesc.idVendor, devdesc.idProduct);
+	  }
+	}
 
      /*
       * Re-attach "usblp" kernel module if it was attached before using this
       * device
       */
       if (printer->usblp_attached == 1)
-	if (libusb_attach_kernel_driver(printer->handle, printer->iface) < 0)
+	if (libusb_attach_kernel_driver(printer->handle, number1) < 0)
 	{
 	  errcode = libusb_get_device_descriptor (printer->device, &devdesc);
 	  if (errcode < 0)
@@ -629,9 +692,11 @@
 		    "DEBUG: Failed to re-attach \"usblp\" kernel module to "
 		    "%04x:%04x\n", devdesc.idVendor, devdesc.idProduct);
 	}
-
-      libusb_free_config_descriptor(confptr);
     }
+    else
+      fprintf(stderr,
+	      "DEBUG: Failed to get configuration descriptor %d\n",
+	      printer->conf);
 
    /*
     * Close the interface and return...
@@ -764,7 +829,10 @@
               protocol           = altptr->bInterfaceProtocol;
 	      printer.altset     = altset;
 	      printer.write_endp = write_endp;
-	      printer.read_endp  = read_endp;
+	      if (protocol > 1)
+		printer.read_endp = read_endp;
+	      else
+		printer.read_endp = -1;
 	    }
 	  }
 
@@ -782,16 +850,29 @@
 	      make_device_uri(&printer, device_id, device_uri,
 			      sizeof(device_uri));
 
+	      fprintf(stderr, "DEBUG: Printer found with device ID: %s "
+		      "Device URI: %s\n",
+		      device_id, device_uri);
+
 	      if ((*cb)(&printer, device_uri, device_id, data))
 	      {
-		printer.read_endp  = confptr->interface[printer.iface].
-					   altsetting[printer.altset].
-					   endpoint[printer.read_endp].
-					   bEndpointAddress;
+		fprintf(stderr, "DEBUG: Device protocol: %d\n",
+			printer.protocol);
+		if (printer.read_endp != -1)
+		{
+		  printer.read_endp = confptr->interface[printer.iface].
+					    altsetting[printer.altset].
+					    endpoint[printer.read_endp].
+					    bEndpointAddress;
+		}
+		else
+		  fprintf(stderr, "DEBUG: Uni-directional USB communication " 
+			  "only!\n");
 		printer.write_endp = confptr->interface[printer.iface].
 					   altsetting[printer.altset].
 					   endpoint[printer.write_endp].
 					   bEndpointAddress;
+		libusb_free_config_descriptor(confptr);
 		return (&printer);
               }
 
@@ -1095,8 +1176,12 @@
   * Try opening the printer...
   */
 
-  if (libusb_open(printer->device, &printer->handle) < 0)
+  if ((errcode = libusb_open(printer->device, &printer->handle)) < 0)
+  {
+    fprintf(stderr, "DEBUG: Failed to open device, code: %d\n",
+	    errcode);
     return (-1);
+  }
 
   printer->usblp_attached = 0;
 
@@ -1132,14 +1217,9 @@
   else
   {
     printer->usblp_attached = 0;
-
-    if (errcode != LIBUSB_ERROR_NOT_SUPPORTED)
-    {
-      fprintf(stderr,
-	      "DEBUG: Failed to check whether %04x:%04x has the \"usblp\" "
-	      "kernel module attached\n", devdesc.idVendor, devdesc.idProduct);
-      goto error;
-    }
+    fprintf(stderr, "DEBUG: Failed to check whether %04x:%04x has the \"usblp\" kernel module attached\n",
+	      devdesc.idVendor, devdesc.idProduct);
+    goto error;
   }
 
  /*
@@ -1156,6 +1236,8 @@
 		0, 0, (unsigned char *)&current, 1, 5000) < 0)
     current = 0;			/* Assume not configured */
 
+  printer->origconf = current;
+
   if ((errcode = 
        libusb_get_config_descriptor (printer->device, printer->conf, &confptr))
       < 0)
@@ -1168,6 +1250,8 @@
 
   if (number1 != current)
   {
+    fprintf(stderr, "DEBUG: Switching USB device configuration: %d -> %d\n", 
+	    current, number1);
     if ((errcode = libusb_set_configuration(printer->handle, number1)) < 0)
     {
      /*
@@ -1347,6 +1431,39 @@
 
 
 /*
+ * 'printer_class_soft_reset()' - Do the soft reset request specific to printers
+ *
+ * This soft reset is specific to the printer device class and is much less
+ * invasive than the general USB reset libusb_reset_device(). Especially it
+ * does never happen that the USB addressing and configuration changes. What
+ * is actually done is that all buffers get flushed and the bulk IN and OUT
+ * pipes get reset to their default states. This clears all stall conditions.
+ * See http://cholla.mmto.org/computers/linux/usb/usbprint11.pdf
+ */
+
+static int				/* O - 0 on success, < 0 on error */
+printer_class_soft_reset(usb_printer_t *printer) /* I - Printer */
+{
+  struct libusb_config_descriptor *confptr = NULL;
+                                        /* Pointer to current configuration */
+  int interface;
+
+  if (libusb_get_config_descriptor (printer->device, printer->conf, &confptr)
+      < 0)
+    interface = printer->iface;
+  else
+    interface = confptr->interface[printer->iface].
+      altsetting[printer->altset].bInterfaceNumber;
+  libusb_free_config_descriptor(confptr);
+  return libusb_control_transfer(printer->handle,
+				 LIBUSB_REQUEST_TYPE_CLASS |
+				 LIBUSB_ENDPOINT_OUT |
+				 LIBUSB_RECIPIENT_INTERFACE,
+				 2, 0, interface, NULL, 0, 5000);
+}
+
+
+/*
  * 'read_thread()' - Thread to read the backchannel data on.
  */
 
@@ -1620,7 +1737,7 @@
   * Send the reset...
   */
 
-  libusb_reset_device (g.printer->handle);
+  printer_class_soft_reset (g.printer);
 
  /*
   * Release the I/O lock...