linux-kernel - Re: [PATCH] usb: fix a few cases of -Wfallthrough

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Message-ID: <20201112180006.GA934688@ubuntu-m3-large-x86>
Date:   Thu, 12 Nov 2020 11:00:06 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Gustavo A . R . Silva" <gustavoars@...nel.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Johan Hovold <johan@...nel.org>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com
Subject: Re: [PATCH] usb: fix a few cases of -Wfallthrough

On Tue, Nov 10, 2020 at 05:47:14PM -0800, Nick Desaulniers wrote:
> The "fallthrough" pseudo-keyword was added as a portable way to denote
> intentional fallthrough. Clang will still warn on cases where there is a
> fallthrough to an immediate break. Add explicit breaks for those cases.
> 
> Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>

Aside from a minor nit/question below:

Reviewed-by: Nathan Chancellor <natechancellor@...il.com>

> ---
>  drivers/usb/core/config.c    | 1 +
>  drivers/usb/host/ehci-hcd.c  | 2 +-
>  drivers/usb/host/ohci-hcd.c  | 2 +-
>  drivers/usb/host/ohci-hub.c  | 1 +
>  drivers/usb/host/xhci-ring.c | 2 ++
>  5 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/core/config.c b/drivers/usb/core/config.c
> index 562a730befda..b199eb65f378 100644
> --- a/drivers/usb/core/config.c
> +++ b/drivers/usb/core/config.c
> @@ -1076,6 +1076,7 @@ int usb_get_bos_descriptor(struct usb_device *dev)
>  		case USB_PTM_CAP_TYPE:
>  			dev->bos->ptm_cap =
>  				(struct usb_ptm_cap_descriptor *)buffer;
> +			break;
>  		default:
>  			break;
>  		}
> diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c
> index 3575b7201881..e358ae17d51e 100644
> --- a/drivers/usb/host/ehci-hcd.c
> +++ b/drivers/usb/host/ehci-hcd.c
> @@ -867,7 +867,7 @@ static int ehci_urb_enqueue (
>  		 */
>  		if (urb->transfer_buffer_length > (16 * 1024))
>  			return -EMSGSIZE;
> -		/* FALLTHROUGH */
> +		fallthrough;

This is fixing the same kind of warnings but it is not called out in the
commit message. Maybe this hunk and the next hunk should be in a
separate patch? No strong preference either way.

>  	/* case PIPE_BULK: */
>  	default:
>  		if (!qh_urb_transaction (ehci, urb, &qtd_list, mem_flags))
> diff --git a/drivers/usb/host/ohci-hcd.c b/drivers/usb/host/ohci-hcd.c
> index 73e13e7c2b46..1f5e69314a17 100644
> --- a/drivers/usb/host/ohci-hcd.c
> +++ b/drivers/usb/host/ohci-hcd.c
> @@ -171,7 +171,7 @@ static int ohci_urb_enqueue (
>  
>  			/* 1 TD for setup, 1 for ACK, plus ... */
>  			size = 2;
> -			/* FALLTHROUGH */
> +			fallthrough;
>  		// case PIPE_INTERRUPT:
>  		// case PIPE_BULK:
>  		default:
> diff --git a/drivers/usb/host/ohci-hub.c b/drivers/usb/host/ohci-hub.c
> index 44504c1751e0..f474f2f9c1e4 100644
> --- a/drivers/usb/host/ohci-hub.c
> +++ b/drivers/usb/host/ohci-hub.c
> @@ -692,6 +692,7 @@ int ohci_hub_control(
>  		case C_HUB_OVER_CURRENT:
>  			ohci_writel (ohci, RH_HS_OCIC,
>  					&ohci->regs->roothub.status);
> +			break;
>  		case C_HUB_LOCAL_POWER:
>  			break;
>  		default:
> diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
> index 167dae117f73..eac43a7b7f23 100644
> --- a/drivers/usb/host/xhci-ring.c
> +++ b/drivers/usb/host/xhci-ring.c
> @@ -2418,6 +2418,7 @@ static int handle_tx_event(struct xhci_hcd *xhci,
>  			xhci_warn_ratelimited(xhci,
>  					      "WARN Successful completion on short TX for slot %u ep %u: needs XHCI_TRUST_TX_LENGTH quirk?\n",
>  					      slot_id, ep_index);
> +		break;
>  	case COMP_SHORT_PACKET:
>  		break;
>  	/* Completion codes for endpoint stopped state */
> @@ -2962,6 +2963,7 @@ static int prepare_ring(struct xhci_hcd *xhci, struct xhci_ring *ep_ring,
>  		return -EINVAL;
>  	case EP_STATE_HALTED:
>  		xhci_dbg(xhci, "WARN halted endpoint, queueing URB anyway.\n");
> +		break;
>  	case EP_STATE_STOPPED:
>  	case EP_STATE_RUNNING:
>  		break;
> -- 
> 2.29.2.222.g5d2a92d10f8-goog
>