Re: [PATCH 19.11 v2] igb_uio: fix build for switch fall through

[Christian Ehrhardt <christian.ehrhardt@canonical.com>]

On Thu, Dec 16, 2021 at 1:36 PM Ferruh Yigit <ferruh.yigit@intel.com> wrote:
>
> Linux is using '-Wimplicit-fallthrough=5' compiler option, which doesn't
> take any fall through comments into account but only uses compiler
> 'fallthrough' attribute to document fall through action is intended.
>
> "falls through" comment was used in the code which is causing a build
> error now, this patch converts comment to the 'fallthrough' macro
> defined in the Linux.
>
> To cover the case where Linux version doesn't have the macro, defined it
> in the compatibility header too.

Thank you Ferruh, I've applied it to the WIP branch for test builds.
If nothing regresses I'll keep it and it will go into -rc2 later.

> Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
> ---
> Cc: Christian Ehrhardt <christian.ehrhardt@canonical.com>
>
> v2:
> * Add both dummy and attribute fallthrough macro definition to
>   compatibility header.
> ---
>  kernel/linux/igb_uio/compat.h  | 14 ++++++++++++++
>  kernel/linux/igb_uio/igb_uio.c |  6 +++---
>  2 files changed, 17 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/linux/igb_uio/compat.h b/kernel/linux/igb_uio/compat.h
> index 8dbb896ae118..850b359f3643 100644
> --- a/kernel/linux/igb_uio/compat.h
> +++ b/kernel/linux/igb_uio/compat.h
> @@ -152,3 +152,17 @@ static inline bool igbuio_kernel_is_locked_down(void)
>         return false;
>  #endif
>  }
> +
> +#ifndef fallthrough
> +
> +#ifndef __has_attribute
> +#define __has_attribute(x) 0
> +#endif
> +
> +#if __has_attribute(__fallthrough__)
> +#define fallthrough    __attribute__((__fallthrough__))
> +#else
> +#define fallthrough    do {} while (0)
> +#endif
> +
> +#endif
> diff --git a/kernel/linux/igb_uio/igb_uio.c b/kernel/linux/igb_uio/igb_uio.c
> index 039f5a5f6354..57d0c58ab1b8 100644
> --- a/kernel/linux/igb_uio/igb_uio.c
> +++ b/kernel/linux/igb_uio/igb_uio.c
> @@ -236,7 +236,7 @@ igbuio_pci_enable_interrupts(struct rte_uio_pci_dev *udev)
>                 }
>  #endif
>
> -       /* falls through - to MSI */
> +       fallthrough;
>         case RTE_INTR_MODE_MSI:
>  #ifndef HAVE_ALLOC_IRQ_VECTORS
>                 if (pci_enable_msi(udev->pdev) == 0) {
> @@ -255,7 +255,7 @@ igbuio_pci_enable_interrupts(struct rte_uio_pci_dev *udev)
>                         break;
>                 }
>  #endif
> -       /* falls through - to INTX */
> +       fallthrough;
>         case RTE_INTR_MODE_LEGACY:
>                 if (pci_intx_mask_supported(udev->pdev)) {
>                         dev_dbg(&udev->pdev->dev, "using INTX");
> @@ -265,7 +265,7 @@ igbuio_pci_enable_interrupts(struct rte_uio_pci_dev *udev)
>                         break;
>                 }
>                 dev_notice(&udev->pdev->dev, "PCI INTX mask not supported\n");
> -       /* falls through - to no IRQ */
> +       fallthrough;
>         case RTE_INTR_MODE_NONE:
>                 udev->mode = RTE_INTR_MODE_NONE;
>                 udev->info.irq = UIO_IRQ_NONE;
> --
> 2.33.1
>


-- 
Christian Ehrhardt
Staff Engineer, Ubuntu Server
Canonical Ltd