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

[shuah]

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