linux-kernel - [PATCH v6] USB hub_probe: rework ugly goto-into-compound-statement

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Date:   Sat, 19 Nov 2016 09:55:45 +0300
From:   Eugene Korenevsky <ekorenevsky@...il.com>
To:     linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Baolin Wang <baolin.wang@...aro.org>
Subject: [PATCH v6] USB hub_probe: rework ugly goto-into-compound-statement

Rework smelling code (goto inside compound statement). Perhaps this is
legacy. Anyway such code is not appropriate for Linux kernel.

Signed-off-by: Eugene Korenevsky <ekorenevsky@...il.com>
---
Changes in v6: more pedantic conversion from `int` to `bool`; fix comment
Changes in v5: make `bool` a return type of `hub_check_descriptor_sanity()`
Changes in v4: fix typo
Changes in v3: extract the code to static function
Changes in v2: fix spaces instead of tab, add missing 'Signed-off-by'

 drivers/usb/core/hub.c | 38 +++++++++++++++++++++-----------------
 1 file changed, 21 insertions(+), 17 deletions(-)

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index cbb1467..dbebfe4 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -1722,10 +1722,28 @@ static void hub_disconnect(struct usb_interface *intf)
 	kref_put(&hub->kref, hub_release);
 }
 
+static bool hub_check_descriptor_sanity(struct usb_host_interface *desc)
+{
+	/* Some hubs have a subclass of 1, which AFAICT according to the */
+	/*  specs is not defined, but it works */
+	if (desc->desc.bInterfaceSubClass != 0 &&
+	    desc->desc.bInterfaceSubClass != 1)
+		return false;
+
+	/* Multiple endpoints? What kind of mutant ninja-hub is this? */
+	if (desc->desc.bNumEndpoints != 1)
+		return false;
+
+	/* If the first endpoint is not interrupt IN, we'd better punt! */
+	if (!usb_endpoint_is_int_in(&desc->endpoint[0].desc))
+		return false;
+
+        return true;
+}
+
 static int hub_probe(struct usb_interface *intf, const struct usb_device_id *id)
 {
 	struct usb_host_interface *desc;
-	struct usb_endpoint_descriptor *endpoint;
 	struct usb_device *hdev;
 	struct usb_hub *hub;
 
@@ -1800,25 +1818,11 @@ static int hub_probe(struct usb_interface *intf, const struct usb_device_id *id)
 	}
 #endif
 
-	/* Some hubs have a subclass of 1, which AFAICT according to the */
-	/*  specs is not defined, but it works */
-	if ((desc->desc.bInterfaceSubClass != 0) &&
-	    (desc->desc.bInterfaceSubClass != 1)) {
-descriptor_error:
+	if (!hub_check_descriptor_sanity(desc)) {
 		dev_err(&intf->dev, "bad descriptor, ignoring hub\n");
 		return -EIO;
 	}
 
-	/* Multiple endpoints? What kind of mutant ninja-hub is this? */
-	if (desc->desc.bNumEndpoints != 1)
-		goto descriptor_error;
-
-	endpoint = &desc->endpoint[0].desc;
-
-	/* If it's not an interrupt in endpoint, we'd better punt! */
-	if (!usb_endpoint_is_int_in(endpoint))
-		goto descriptor_error;
-
 	/* We found a hub */
 	dev_info(&intf->dev, "USB hub found\n");
 
@@ -1845,7 +1849,7 @@ static int hub_probe(struct usb_interface *intf, const struct usb_device_id *id)
 	if (id->driver_info & HUB_QUIRK_CHECK_PORT_AUTOSUSPEND)
 		hub->quirk_check_port_auto_suspend = 1;
 
-	if (hub_configure(hub, endpoint) >= 0)
+	if (hub_configure(hub, &desc->endpoint[0].desc) >= 0)
 		return 0;
 
 	hub_disconnect(intf);
-- 
2.10.2