linux-kernel - Re: [PATCH 5/5] gma500: fix a missing break in psb_driver

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Date:   Fri, 1 Apr 2022 12:10:48 +0200
From:   Patrik Jakobsson <patrik.r.jakobsson@...il.com>
To:     Xiaomeng Tong <xiam0nd.tong@...il.com>
Cc:     David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        Zhao Yakui <yakui.zhao@...el.com>,
        Dave Airlie <airlied@...hat.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/5] gma500: fix a missing break in psb_driver_load

On Wed, Mar 30, 2022 at 2:03 PM Xiaomeng Tong <xiam0nd.tong@...il.com> wrote:
>
> Instead of exiting the loop as expected when an entry is found, the
> list_for_each_entry() continues until the traversal is complete. To
> avoid potential executing 'ret = gma_backlight_init(dev);' repeatly,
> add a break after the switch statement.
>
> Fixes: 5c49fd3aa0ab0 ("gma500: Add the core DRM files and headers")
> Signed-off-by: Xiaomeng Tong <xiam0nd.tong@...il.com>

This is incorrect. If we always break on the first iteration we will
only run gma_backlight_init() if the first connector is LVDS or MIPI.
This might not be the case and gma_backlight_init() will never run.
The other loops you have been looking at have an "if (xxx != yyy)
continue;" statement at the top which skips all the unwanted entries
but this loop does not.

> ---
>  drivers/gpu/drm/gma500/psb_drv.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/gpu/drm/gma500/psb_drv.c b/drivers/gpu/drm/gma500/psb_drv.c
> index 65cf1c79dd7c..d65a68811bf7 100644
> --- a/drivers/gpu/drm/gma500/psb_drv.c
> +++ b/drivers/gpu/drm/gma500/psb_drv.c
> @@ -398,6 +398,8 @@ static int psb_driver_load(struct drm_device *dev, unsigned long flags)
>                         ret = gma_backlight_init(dev);
>                         break;
>                 }
> +
> +               break;
>         }
>
>         if (ret)
> --
> 2.17.1
>