linux-kernel - Re: [PATCH] drm/vmwgfx: use *_32

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Date:	Thu, 14 Apr 2016 13:32:20 +0200
From:	Paul Bolle <pebolle@...cali.nl>
To:	David Airlie <airlied@...ux.ie>
Cc:	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/vmwgfx: use *_32_bits() macros

On do, 2016-03-03 at 11:26 +0100, Paul Bolle wrote:
> Use the upper_32_bits() macro instead of the four line equivalent that
> triggers a GCC warning on 32 bits x86:
>     drivers/gpu/drm/vmwgfx/vmwgfx_cmdbuf.c: In function
> 'vmw_cmdbuf_header_submit':
>     drivers/gpu/drm/vmwgfx/vmwgfx_cmdbuf.c:297:25: warning: right
> shift count >= width of type [-Wshift-count-overflow]
>        val = (header->handle >> 32);
>                              ^
> 
> And use the lower_32_bits() macro instead of and-ing with a 32 bits
> mask.
> 
> Signed-off-by: Paul Bolle <pebolle@...cali.nl>
> ---
> Note: compile tested only (I don't use any of vmware's products).

The warning can still be seen on v4.6-rc3 for 32 bits x86. This patch
applies cleanly to that rc.

Has anyone had a chance to look at this patch, and perhaps even test it?

Thanks,


Paul Bolle

>  drivers/gpu/drm/vmwgfx/vmwgfx_cmdbuf.c | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_cmdbuf.c
> b/drivers/gpu/drm/vmwgfx/vmwgfx_cmdbuf.c
> index 67cebb23c940..aa04fb0159a7 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_cmdbuf.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_cmdbuf.c
> @@ -293,13 +293,10 @@ static int vmw_cmdbuf_header_submit(struct
> vmw_cmdbuf_header *header)
>  	struct vmw_cmdbuf_man *man = header->man;
>  	u32 val;
>  
> -	if (sizeof(header->handle) > 4)
> -		val = (header->handle >> 32);
> -	else
> -		val = 0;
> +	val = upper_32_bits(header->handle);
>  	vmw_write(man->dev_priv, SVGA_REG_COMMAND_HIGH, val);
>  
> -	val = (header->handle & 0xFFFFFFFFULL);
> +	val = lower_32_bits(header->handle);
>  	val |= header->cb_context & SVGA_CB_CONTEXT_MASK;
>  	vmw_write(man->dev_priv, SVGA_REG_COMMAND_LOW, val);
>