Re: [PATCH 1/2] drm/i915: Squelch smatch warning for statement with no effect

[Jani Nikula <jani.nikula@linux.intel.com>]

On Fri, 20 Jan 2017, Chris Wilson <chris@chris-wilson.co.uk> wrote:
> The sgt iterators cause an
>
> drivers/gpu/drm/i915/i915_gpu_error.c:846 i915_error_object_create() warn: statement has no effect 7
>
> everywhere they are used. If we change the code slightly, we can achieve
> the same increment without altering the output or raising a warning.

I've never liked using logical OR short circuiting for assignments like
this anyway, so I think this is an improvement no matter what.

Reviewed-by: Jani Nikula <jani.nikula@intel.com>


>
>    text	   data	    bss	    dec	    hex	filename
> 1267906	  20587	   3168	1291661	 13b58d	before
> 1267906	  20587	   3168	1291661	 13b58d	after
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/i915_drv.h | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 1b340eb0db19..ebe2f6c737f7 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -2620,8 +2620,8 @@ static inline struct scatterlist *__sg_next(struct scatterlist *sg)
>  #define for_each_sgt_dma(__dmap, __iter, __sgt)				\
>  	for ((__iter) = __sgt_iter((__sgt)->sgl, true);			\
>  	     ((__dmap) = (__iter).dma + (__iter).curr);			\
> -	     (((__iter).curr += PAGE_SIZE) < (__iter).max) ||		\
> -	     ((__iter) = __sgt_iter(__sg_next((__iter).sgp), true), 0))
> +	     (((__iter).curr += PAGE_SIZE) >= (__iter).max) ?		\
> +	     (__iter) = __sgt_iter(__sg_next((__iter).sgp), true), 0 : 0)
>  
>  /**
>   * for_each_sgt_page - iterate over the pages of the given sg_table
> @@ -2633,8 +2633,8 @@ static inline struct scatterlist *__sg_next(struct scatterlist *sg)
>  	for ((__iter) = __sgt_iter((__sgt)->sgl, false);		\
>  	     ((__pp) = (__iter).pfn == 0 ? NULL :			\
>  	      pfn_to_page((__iter).pfn + ((__iter).curr >> PAGE_SHIFT))); \
> -	     (((__iter).curr += PAGE_SIZE) < (__iter).max) ||		\
> -	     ((__iter) = __sgt_iter(__sg_next((__iter).sgp), false), 0))
> +	     (((__iter).curr += PAGE_SIZE) >= (__iter).max) ?		\
> +	     (__iter) = __sgt_iter(__sg_next((__iter).sgp), false), 0 : 0)
>  
>  static inline const struct intel_device_info *
>  intel_info(const struct drm_i915_private *dev_priv)

-- 
Jani Nikula, Intel Open Source Technology Center
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