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

[Gustavo A. R. Silva]

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;
	}

Thanks
--
Gustavo