USB: core: add helpers to retrieve endpoints in reverse order

Several drivers have implemented their endpoint look-up loops in such a
way that they have picked the last endpoint descriptor of the specified
type should more than one such descriptor exist.

To avoid any regressions, add corresponding helpers to lookup endpoints
by searching the endpoint descriptors in reverse order.

Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 76 insertions, 36 deletions

diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index 5d65504770f5..1ec9d248781e 100644
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -74,6 +74,48 @@ MODULE_PARM_DESC(autosuspend, "default autosuspend delay");
 #define usb_autosuspend_delay		0
 #endif
 
+static bool match_endpoint(struct usb_endpoint_descriptor *epd,
+		struct usb_endpoint_descriptor **bulk_in,
+		struct usb_endpoint_descriptor **bulk_out,
+		struct usb_endpoint_descriptor **int_in,
+		struct usb_endpoint_descriptor **int_out)
+{
+	switch (usb_endpoint_type(epd)) {
+	case USB_ENDPOINT_XFER_BULK:
+		if (usb_endpoint_dir_in(epd)) {
+			if (bulk_in && !*bulk_in) {
+				*bulk_in = epd;
+				break;
+			}
+		} else {
+			if (bulk_out && !*bulk_out) {
+				*bulk_out = epd;
+				break;
+			}
+		}
+
+		return false;
+	case USB_ENDPOINT_XFER_INT:
+		if (usb_endpoint_dir_in(epd)) {
+			if (int_in && !*int_in) {
+				*int_in = epd;
+				break;
+			}
+		} else {
+			if (int_out && !*int_out) {
+				*int_out = epd;
+				break;
+			}
+		}
+
+		return false;
+	default:
+		return false;
+	}
+
+	return (!bulk_in || *bulk_in) && (!bulk_out || *bulk_out) &&
+			(!int_in || *int_in) && (!int_out || *int_out);
+}
 
 /**
  * usb_find_common_endpoints() -- look up common endpoint descriptors
@@ -113,50 +155,48 @@ int usb_find_common_endpoints(struct usb_host_interface *alt,
 	for (i = 0; i < alt->desc.bNumEndpoints; ++i) {
 		epd = &alt->endpoint[i].desc;
 
-		switch (usb_endpoint_type(epd)) {
-		case USB_ENDPOINT_XFER_BULK:
-			if (usb_endpoint_dir_in(epd)) {
-				if (bulk_in && !*bulk_in) {
-					*bulk_in = epd;
-					break;
-				}
-			} else {
-				if (bulk_out && !*bulk_out) {
-					*bulk_out = epd;
-					break;
-				}
-			}
+		if (match_endpoint(epd, bulk_in, bulk_out, int_in, int_out))
+			return 0;
+	}
 
-			continue;
-		case USB_ENDPOINT_XFER_INT:
-			if (usb_endpoint_dir_in(epd)) {
-				if (int_in && !*int_in) {
-					*int_in = epd;
-					break;
-				}
-			} else {
-				if (int_out && !*int_out) {
-					*int_out = epd;
-					break;
-				}
-			}
+	return -ENXIO;
+}
+EXPORT_SYMBOL_GPL(usb_find_common_endpoints);
 
-			continue;
-		default:
-			continue;
-		}
+/**
+ * usb_find_common_endpoints_reverse() -- look up common endpoint descriptors
+ *
+ * Same as usb_find_common_endpoints(), but the endpoint descriptors are
+ * searched in reverse order (see usb_find_common_endpoints() for details).
+ */
+int usb_find_common_endpoints_reverse(struct usb_host_interface *alt,
+		struct usb_endpoint_descriptor **bulk_in,
+		struct usb_endpoint_descriptor **bulk_out,
+		struct usb_endpoint_descriptor **int_in,
+		struct usb_endpoint_descriptor **int_out)
+{
+	struct usb_endpoint_descriptor *epd;
+	int i;
+
+	if (bulk_in)
+		*bulk_in = NULL;
+	if (bulk_out)
+		*bulk_out = NULL;
+	if (int_in)
+		*int_in = NULL;
+	if (int_out)
+		*int_out = NULL;
+
+	for (i = alt->desc.bNumEndpoints - 1; i >= 0; --i) {
+		epd = &alt->endpoint[i].desc;
 
-		if ((!bulk_in || *bulk_in) &&
-				(!bulk_out || *bulk_out) &&
-				(!int_in || *int_in) &&
-				(!int_out || *int_out)) {
+		if (match_endpoint(epd, bulk_in, bulk_out, int_in, int_out))
 			return 0;
-		}
 	}
 
 	return -ENXIO;
 }
-EXPORT_SYMBOL_GPL(usb_find_common_endpoints);
+EXPORT_SYMBOL_GPL(usb_find_common_endpoints_reverse);
 
 /**
  * usb_find_alt_setting() - Given a configuration, find the alternate setting