Re: [PATCH] drm/i915: Fix kzalloc() smatch warnings in get_initial_plane_config()

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Jan 21, 2015 at 01:50:54PM +0000, Damien Lespiau wrote:
> Smatch doesn't like:
> 
>   struct drm_framebuffer *fb;
>   fb = kzalloc(sizeof(struct intel_framebuffer), GFP_KERNEL);
> 
> and warns with:
> 
>   warn: struct type mismatch 'drm_framebuffer vs intel_framebuffer'
> 
> This implicit cast was correct as struct intel_framebuffer has struct
> drm_framebuffer as its first member, but in case someone want to reorder
> the fields for some reason, it's slightly safer to access the underlying
> drm_framebuffer through intel_fb->base.
> 
> Also, having fewer static analysis warnings is a worthy goal.
> 
> Cc: kbuild@01.org
> Cc: Dan Carpenter <dan.carpenter@oracle.com>
> Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 21 +++++++++++++++------
>  1 file changed, 15 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 65fce56..01dc80b 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -6584,13 +6584,16 @@ i9xx_get_initial_plane_config(struct intel_crtc *crtc,
>  	int fourcc, pixel_format;
>  	int aligned_height;
>  	struct drm_framebuffer *fb;
> +	struct intel_framebuffer *intel_fb;
>  
> -	fb = kzalloc(sizeof(struct intel_framebuffer), GFP_KERNEL);
> -	if (!fb) {
> +	intel_fb = kzalloc(sizeof(struct intel_framebuffer), GFP_KERNEL);

sizeof(*intel_fb) while at it?

> +	if (!intel_fb) {
>  		DRM_DEBUG_KMS("failed to alloc fb\n");
>  		return;
>  	}
>  
> +	fb = &intel_fb->base;
> +
>  	val = I915_READ(DSPCNTR(plane));
>  
>  	if (INTEL_INFO(dev)->gen >= 4)
> @@ -7613,13 +7616,16 @@ skylake_get_initial_plane_config(struct intel_crtc *crtc,
>  	int fourcc, pixel_format;
>  	int aligned_height;
>  	struct drm_framebuffer *fb;
> +	struct intel_framebuffer *intel_fb;
>  
> -	fb = kzalloc(sizeof(struct intel_framebuffer), GFP_KERNEL);
> -	if (!fb) {
> +	intel_fb = kzalloc(sizeof(struct intel_framebuffer), GFP_KERNEL);
> +	if (!intel_fb) {
>  		DRM_DEBUG_KMS("failed to alloc fb\n");
>  		return;
>  	}
>  
> +	fb = &intel_fb->base;
> +
>  	val = I915_READ(PLANE_CTL(pipe, 0));
>  	if (val & PLANE_CTL_TILED_MASK)
>  		plane_config->tiling = I915_TILING_X;
> @@ -7706,13 +7712,16 @@ ironlake_get_initial_plane_config(struct intel_crtc *crtc,
>  	int fourcc, pixel_format;
>  	int aligned_height;
>  	struct drm_framebuffer *fb;
> +	struct intel_framebuffer *intel_fb;
>  
> -	fb = kzalloc(sizeof(struct intel_framebuffer), GFP_KERNEL);
> -	if (!fb) {
> +	intel_fb = kzalloc(sizeof(struct intel_framebuffer), GFP_KERNEL);
> +	if (!intel_fb) {
>  		DRM_DEBUG_KMS("failed to alloc fb\n");
>  		return;
>  	}
>  
> +	fb = &intel_fb->base;
> +
>  	val = I915_READ(DSPCNTR(pipe));
>  
>  	if (INTEL_INFO(dev)->gen >= 4)
> -- 
> 1.8.3.1
> 
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-- 
Ville Syrjälä
Intel OTC
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