[PATCH v5] USB hub_probe: rework ugly goto-into-compound-statement

[PATCH v5] USB hub_probe: rework ugly goto-into-compound-statement

[Eugene Korenevsky]

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@gmail.com>
---
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 | 35 ++++++++++++++++++-----------------
 1 file changed, 18 insertions(+), 17 deletions(-)

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index cbb1467..1a316a1 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -1722,10 +1722,25 @@ 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 it's not an interrupt in endpoint, we'd better punt! */
+	return usb_endpoint_is_int_in(&desc->endpoint[0].desc) != 0;
+}
+
 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 +1815,11 @@ 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 +1846,7 @@ 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

Re: [PATCH v5] USB hub_probe: rework ugly goto-into-compound-statement

[Greg Kroah-Hartman]

On Sun, Nov 13, 2016 at 03:53:58PM +0300, Eugene Korenevsky wrote:
> 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@gmail.com>
> ---
> 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 | 35 ++++++++++++++++++-----------------
>  1 file changed, 18 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index cbb1467..1a316a1 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -1722,10 +1722,25 @@ 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 it's not an interrupt in endpoint, we'd better punt! */
> +	return usb_endpoint_is_int_in(&desc->endpoint[0].desc) != 0;

Ok, I'm going to be really pedantic here and ask that you spell this
last statement out:
	if (usb...)
		return true;
	return false;

thanks,

greg k-h

Re: [PATCH v5] USB hub_probe: rework ugly goto-into-compound-statement

[Greg Kroah-Hartman]

On Sun, Nov 13, 2016 at 03:53:58PM +0300, Eugene Korenevsky wrote:
> 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@gmail.com>
> ---
> 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 | 35 ++++++++++++++++++-----------------
>  1 file changed, 18 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index cbb1467..1a316a1 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -1722,10 +1722,25 @@ 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 it's not an interrupt in endpoint, we'd better punt! */
> +	return usb_endpoint_is_int_in(&desc->endpoint[0].desc) != 0;

Also, the comment should say:
	/* If the first endpoint is not interrupt IN, we... */

Re: [PATCH v5] USB hub_probe: rework ugly goto-into-compound-statement

[Eugene Korenevsky]

> Ok, I'm going to be really pedantic here and ask that you spell this
> last statement out:
>        if (usb...)
>                 return true;
>        return false;


> 
> Also, the comment should say:
> 	/* If the first endpoint is not interrupt IN, we... */
> 

It's better to inverse the condition and return false:

```
if (!usb...)
        return false;
return true;
```

This is exactly what is said in the comment ("If the first endpoint...
we'd better punt!"). And does not break the composition of the entire
function (all `if` bodies return false, last statement is `return
true`).

-- 
Eugene