[PATCH] drm/i915: Replace __I915__ with typesafe variant

[PATCH] drm/i915: Replace __I915__ with typesafe variant

[Chris Wilson]

Ville pointed out the GCCism __builtin_types_compatible_p() that we
could use to replace our heavily casted presumption __I915__ macro that
was based on comparing struct sizes.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_dma.c |  3 ---
 drivers/gpu/drm/i915/i915_drv.h | 12 ++++++++++--
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 5e3b1390ac5c..b2e4dbcb77ae 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -1582,9 +1582,6 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
 	if (!drm_core_check_feature(dev, DRIVER_MODESET) && !dev->agp)
 		return -EINVAL;
 
-	/* For the ugly agnostic INTEL_INFO macro */
-	BUILD_BUG_ON(sizeof(*dev_priv) == sizeof(*dev));
-
 	BUILD_BUG_ON(I915_NUM_RINGS >= (1 << I915_NUM_RING_BITS));
 
 	dev_priv = kzalloc(sizeof(*dev_priv), GFP_KERNEL);
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index d1513e6ea50d..b6dcbf79b31c 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2081,8 +2081,16 @@ struct drm_i915_cmd_table {
 };
 
 /* Note that the (struct drm_i915_private *) cast is just to shut up gcc. */
-#define __I915__(p)	((sizeof(*(p)) == sizeof(struct drm_i915_private)) ? \
-			 (struct drm_i915_private *)(p) : to_i915(p))
+#define __I915__(p) ({ \
+	struct drm_i915_private *__p; \
+	if (__builtin_types_compatible_p(typeof(*p), struct drm_i915_private)) \
+		__p = (struct drm_i915_private *)p; \
+	else if (__builtin_types_compatible_p(typeof(*p), struct drm_device)) \
+		__p = to_i915((struct drm_device *)p); \
+	else \
+		BUILD_BUG(); \
+	__p; \
+})
 #define INTEL_INFO(p) 	(&__I915__(p)->info)
 #define INTEL_DEVID(p)	(INTEL_INFO(p)->device_id)
 
-- 
2.1.0.rc1

Re: [PATCH] drm/i915: Replace __I915__ with typesafe variant

[Daniel Vetter]

On Wed, Aug 13, 2014 at 12:14:12PM +0100, Chris Wilson wrote:
> Ville pointed out the GCCism __builtin_types_compatible_p() that we
> could use to replace our heavily casted presumption __I915__ macro that
> was based on comparing struct sizes.
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

Yeah, that looks a bit less crazy. Queued for -next, thanks for the patch.
-Daniel

> ---
>  drivers/gpu/drm/i915/i915_dma.c |  3 ---
>  drivers/gpu/drm/i915/i915_drv.h | 12 ++++++++++--
>  2 files changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
> index 5e3b1390ac5c..b2e4dbcb77ae 100644
> --- a/drivers/gpu/drm/i915/i915_dma.c
> +++ b/drivers/gpu/drm/i915/i915_dma.c
> @@ -1582,9 +1582,6 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
>  	if (!drm_core_check_feature(dev, DRIVER_MODESET) && !dev->agp)
>  		return -EINVAL;
>  
> -	/* For the ugly agnostic INTEL_INFO macro */
> -	BUILD_BUG_ON(sizeof(*dev_priv) == sizeof(*dev));
> -
>  	BUILD_BUG_ON(I915_NUM_RINGS >= (1 << I915_NUM_RING_BITS));
>  
>  	dev_priv = kzalloc(sizeof(*dev_priv), GFP_KERNEL);
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index d1513e6ea50d..b6dcbf79b31c 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -2081,8 +2081,16 @@ struct drm_i915_cmd_table {
>  };
>  
>  /* Note that the (struct drm_i915_private *) cast is just to shut up gcc. */
> -#define __I915__(p)	((sizeof(*(p)) == sizeof(struct drm_i915_private)) ? \
> -			 (struct drm_i915_private *)(p) : to_i915(p))
> +#define __I915__(p) ({ \
> +	struct drm_i915_private *__p; \
> +	if (__builtin_types_compatible_p(typeof(*p), struct drm_i915_private)) \
> +		__p = (struct drm_i915_private *)p; \
> +	else if (__builtin_types_compatible_p(typeof(*p), struct drm_device)) \
> +		__p = to_i915((struct drm_device *)p); \
> +	else \
> +		BUILD_BUG(); \
> +	__p; \
> +})
>  #define INTEL_INFO(p) 	(&__I915__(p)->info)
>  #define INTEL_DEVID(p)	(INTEL_INFO(p)->device_id)
>  
> -- 
> 2.1.0.rc1
> 
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch