USB: indicate active altsetting in proc/bus/usb/devices file

Update /proc/bus/usb/devices output to report active altsettings.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

Documentation/usb/proc_usb_info.txt

@@ -213,15 +213,16 @@ C:* #Ifs=dd Cfg#=dd Atr=xx MPwr=dddmA
 
 Interface descriptor info (can be multiple per Config):
 
-I:  If#=dd Alt=dd #EPs=dd Cls=xx(sssss) Sub=xx Prot=xx Driver=ssss
-|   |      |      |       |             |      |       |__Driver name
-|   |      |      |       |             |      |          or "(none)"
-|   |      |      |       |             |      |__InterfaceProtocol
-|   |      |      |       |             |__InterfaceSubClass
-|   |      |      |       |__InterfaceClass
-|   |      |      |__NumberOfEndpoints
-|   |      |__AlternateSettingNumber
-|   |__InterfaceNumber
+I:* If#=dd Alt=dd #EPs=dd Cls=xx(sssss) Sub=xx Prot=xx Driver=ssss
+| | |      |      |       |             |      |       |__Driver name
+| | |      |      |       |             |      |          or "(none)"
+| | |      |      |       |             |      |__InterfaceProtocol
+| | |      |      |       |             |__InterfaceSubClass
+| | |      |      |       |__InterfaceClass
+| | |      |      |__NumberOfEndpoints
+| | |      |__AlternateSettingNumber
+| | |__InterfaceNumber
+| |__ "*" indicates the active altsetting (others are " ")
 |__Interface info tag
 
     A given interface may have one or more "alternate" settings.
@@ -277,7 +278,7 @@ of the USB devices on a system's root hub.  (See more below
 on how to do this.)
 
 The Interface lines can be used to determine what driver is
-being used for each device.
+being used for each device, and which altsetting it activated.
 
 The Configuration lines could be used to list maximum power
 (in milliamps) that a system's USB devices are using.

drivers/usb/core/devices.c

@@ -104,7 +104,7 @@ static const char *format_config =
   
 static const char *format_iface =
 /* I:  If#=dd Alt=dd #EPs=dd Cls=xx(sssss) Sub=xx Prot=xx Driver=xxxx*/
-  "I:  If#=%2d Alt=%2d #EPs=%2d Cls=%02x(%-5s) Sub=%02x Prot=%02x Driver=%s\n";
+  "I:%c If#=%2d Alt=%2d #EPs=%2d Cls=%02x(%-5s) Sub=%02x Prot=%02x Driver=%s\n";
 
 static const char *format_endpt =
 /* E:  Ad=xx(s) Atr=xx(ssss) MxPS=dddd Ivl=D?s */
@@ -242,15 +242,19 @@ static char *usb_dump_interface_descriptor(char *start, char *end,
 {
 	const struct usb_interface_descriptor *desc = &intfc->altsetting[setno].desc;
 	const char *driver_name = "";
+	int active = 0;
 
 	if (start > end)
 		return start;
 	down_read(&usb_bus_type.subsys.rwsem);
-	if (iface)
+	if (iface) {
 		driver_name = (iface->dev.driver
 				? iface->dev.driver->name
 				: "(none)");
+		active = (desc == &iface->cur_altsetting->desc);
+	}
 	start += sprintf(start, format_iface,
+			 active ? '*' : ' ',	/* mark active altsetting */
 			 desc->bInterfaceNumber,
 			 desc->bAlternateSetting,
 			 desc->bNumEndpoints,