linux-kernel - [PATCH] PCI: Mark expected switch fall-throughs

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Message-ID: <20190320182715.GA9406@embeddedor>
Date:   Wed, 20 Mar 2019 13:27:15 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        xen-devel@...ts.xenproject.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Kees Cook <keescook@...omium.org>
Subject: [PATCH] PCI: Mark expected switch fall-throughs

In preparation to enabling -Wimplicit-fallthrough, mark switch
cases where we are expecting to fall through.

This patch fixes the following warnings:

drivers/pci/proc.c: In function ‘proc_bus_pci_ioctl’:
drivers/pci/proc.c:216:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
   if (arch_can_pci_mmap_wc()) {
      ^
drivers/pci/proc.c:225:2: note: here
  default:
  ^~~~~~~

drivers/pci/xen-pcifront.c: In function ‘pcifront_backend_changed’:
drivers/pci/xen-pcifront.c:1105:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
   if (xdev->state == XenbusStateClosed)
      ^
drivers/pci/xen-pcifront.c:1108:2: note: here
  case XenbusStateClosing:
  ^~~~

Notice that, in this particular case, the /* fall through */
comment is placed at the very bottom of the case statement,
which is what GCC is expecting to find.

Warning level 3 was used: -Wimplicit-fallthrough=3

This patch is part of the ongoing efforts to enable
-Wimplicit-fallthrough.

Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
 drivers/pci/proc.c         | 1 +
 drivers/pci/xen-pcifront.c | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/proc.c b/drivers/pci/proc.c
index 6fa1627ce08d..445b51db75b0 100644
--- a/drivers/pci/proc.c
+++ b/drivers/pci/proc.c
@@ -222,6 +222,7 @@ static long proc_bus_pci_ioctl(struct file *file, unsigned int cmd,
 		}
 		/* If arch decided it can't, fall through... */
 #endif /* HAVE_PCI_MMAP */
+		/* fall through */
 	default:
 		ret = -EINVAL;
 		break;
diff --git a/drivers/pci/xen-pcifront.c b/drivers/pci/xen-pcifront.c
index eba6e33147a2..14cf0f41ecf0 100644
--- a/drivers/pci/xen-pcifront.c
+++ b/drivers/pci/xen-pcifront.c
@@ -1104,7 +1104,7 @@ static void __ref pcifront_backend_changed(struct xenbus_device *xdev,
 	case XenbusStateClosed:
 		if (xdev->state == XenbusStateClosed)
 			break;
-		/* Missed the backend's CLOSING state -- fallthrough */
+		/* fall through - Missed the backend's CLOSING state. */
 	case XenbusStateClosing:
 		dev_warn(&xdev->dev, "backend going away!\n");
 		pcifront_try_disconnect(pdev);
-- 
2.21.0