Re: [PATCH] usbip: vhci_hcd: Mark expected switch fall-through

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On 4/30/19 9:44 AM, Greg Kroah-Hartman wrote:
On Mon, Apr 29, 2019 at 10:05:51AM -0500, Gustavo A. R. Silva wrote:


On 4/29/19 9:44 AM, David Laight wrote:
From: Gustavo A. R. Silva
Sent: 29 April 2019 15:40
In preparation to enabling -Wimplicit-fallthrough, mark switch
cases where we are expecting to fall through.
...
diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c
index 667d9c0ec905..000ab7225717 100644
--- a/drivers/usb/usbip/vhci_hcd.c
+++ b/drivers/usb/usbip/vhci_hcd.c
@@ -508,6 +508,7 @@ static int vhci_hub_control(struct usb_hcd *hcd, u16 typeReq, u16 wValue,
  		case USB_PORT_FEAT_U1_TIMEOUT:
  			usbip_dbg_vhci_rh(
  				" SetPortFeature: USB_PORT_FEAT_U1_TIMEOUT\n");
+			/* Fall through */
  		case USB_PORT_FEAT_U2_TIMEOUT:
  			usbip_dbg_vhci_rh(
  				" SetPortFeature: USB_PORT_FEAT_U2_TIMEOUT\n");

That doesn't look right, both debug messages seem to get printed.


At first sight, I thought the same way, then I took a look into
commit:

1c9de5bf428612458427943b724bea51abde520a

and noticed that the original developer properly added fall-through
comments in other places in the same switch() code, that gave me the
impression he knew what he was doing; then I noticed the following
error message in case USB_PORT_FEAT_U2_TIMEOUT:

	if (hcd->speed != HCD_USB3) {
		pr_err("USB_PORT_FEAT_U1/2_TIMEOUT req not "
		       "supported for USB 2.0 roothub\n");
		goto error;
	}

this error message is what makes me think the fall-through is
intentional; otherwise I think it would look like this instead:

	if (hcd->speed != HCD_USB3) {
		pr_err("USB_PORT_FEAT_U2_TIMEOUT req not "
		       "supported for USB 2.0 roothub\n");
		goto error;
	}

I think you are right, that's horrid, but correct :(

Yes. This hub_control is poorly organized and could use cleanup.

Will go queue this up, thanks.


Acked-by: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>

Thanks Greg!. It is on my list of things to Ack today.

-- Shuah



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