linux-kernel - Re: [PATCH] drm: gma500: fix logic error

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Message-ID: <20170905110847.oy2tilpmvu2mkuls@phenom.ffwll.local>
Date:   Tue, 5 Sep 2017 13:08:47 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Patrik Jakobsson <patrik.r.jakobsson@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Ville Syrjälä 
        <ville.syrjala@...ux.intel.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm: gma500: fix logic error

On Tue, Sep 05, 2017 at 09:47:26AM +0200, Arnd Bergmann wrote:
> gcc-8 points out a condition that almost certainly doesn't
> do what the author had in mind:
> 
> drivers/gpu/drm/gma500/mdfld_intel_display.c: In function 'mdfldWaitForPipeEnable':
> drivers/gpu/drm/gma500/mdfld_intel_display.c:102:37: error: bitwise comparison always evaluates to false [-Werror=tautological-compare]
> 
> This changes it to a simple bit mask operation to check
> whether the bit is set.
> 
> Fixes: 026abc333205 ("gma500: initial medfield merge")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Applied to drm-misc, thanks.
-Daniel

> ---
>  drivers/gpu/drm/gma500/mdfld_intel_display.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/gma500/mdfld_intel_display.c b/drivers/gpu/drm/gma500/mdfld_intel_display.c
> index 531e4450c000..5c066448be5b 100644
> --- a/drivers/gpu/drm/gma500/mdfld_intel_display.c
> +++ b/drivers/gpu/drm/gma500/mdfld_intel_display.c
> @@ -99,7 +99,7 @@ void mdfldWaitForPipeEnable(struct drm_device *dev, int pipe)
>  	/* Wait for for the pipe enable to take effect. */
>  	for (count = 0; count < COUNT_MAX; count++) {
>  		temp = REG_READ(map->conf);
> -		if ((temp & PIPEACONF_PIPE_STATE) == 1)
> +		if (temp & PIPEACONF_PIPE_STATE)
>  			break;
>  	}
>  }
> -- 
> 2.9.0
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch