linux-kernel - Re: [PATCH] drm/imx: imx-tve: Fix return type of imx_tve_connector_mode

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Date:   Mon, 31 Oct 2022 14:43:42 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Nathan Huckleberry <nhuck@...gle.com>
Cc:     Dan Carpenter <error27@...il.com>, llvm@...ts.linux.dev,
        Philipp Zabel <p.zabel@...gutronix.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/imx: imx-tve: Fix return type of
 imx_tve_connector_mode_valid

On Tue, Sep 13, 2022 at 01:55:44PM -0700, Nathan Huckleberry wrote:
> The mode_valid field in drm_connector_helper_funcs is expected to be of
> type:
> enum drm_mode_status (* mode_valid) (struct drm_connector *connector,
>                                      struct drm_display_mode *mode);
> 
> The mismatched return type breaks forward edge kCFI since the underlying
> function definition does not match the function hook definition.
> 
> The return type of imx_tve_connector_mode_valid should be changed from
> int to enum drm_mode_status.
> 
> Reported-by: Dan Carpenter <error27@...il.com>
> Link: https://github.com/ClangBuiltLinux/linux/issues/1703
> Cc: llvm@...ts.linux.dev
> Signed-off-by: Nathan Huckleberry <nhuck@...gle.com>

Reviewed-by: Nathan Chancellor <nathan@...nel.org>

Can someone pick this up? It resolves a new work-in-progress clang
warning that we would like to turn on for the kernel:

  drivers/gpu/drm/imx/imx-tve.c:320:16: error: incompatible function pointer types initializing 'enum drm_mode_status (*)(struct drm_connector *, struct drm_display_mode *)' with an expression of type 'int (struct drm_connector *, struct drm_display_mode *)' [-Werror,-Wincompatible-function-pointer-types-strict]
          .mode_valid = imx_tve_connector_mode_valid,
                        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
  1 error generated.

> ---
>  drivers/gpu/drm/imx/imx-tve.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/imx/imx-tve.c b/drivers/gpu/drm/imx/imx-tve.c
> index 6b34fac3f73a..ab4d1c878fda 100644
> --- a/drivers/gpu/drm/imx/imx-tve.c
> +++ b/drivers/gpu/drm/imx/imx-tve.c
> @@ -218,8 +218,9 @@ static int imx_tve_connector_get_modes(struct drm_connector *connector)
>  	return ret;
>  }
>  
> -static int imx_tve_connector_mode_valid(struct drm_connector *connector,
> -					struct drm_display_mode *mode)
> +static enum drm_mode_status
> +imx_tve_connector_mode_valid(struct drm_connector *connector,
> +			     struct drm_display_mode *mode)
>  {
>  	struct imx_tve *tve = con_to_tve(connector);
>  	unsigned long rate;
> -- 
> 2.37.2.789.g6183377224-goog
> 
>