Re: [PATCH] intel: Set bo size from lseek if kernel supports it

[Daniel Vetter <daniel@ffwll.ch>]

On Thu, Oct 10, 2013 at 03:07:01PM -0700, Kristian Høgsberg wrote:
> The various create and open functions set the buffer size, but
> drm_intel_bo_gem_create_from_prime() is an exception.  In the 3.12 kernel
> we can now use lseek on the prime fd to determine the size of the bo.
> Use that and override the userprovided size.  If the kernel doesn't
> support this, we get an error and fall back to the user provided size.
> 
> Signed-off-by: Kristian Høgsberg <krh@bitplanet.net>

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---
>  intel/intel_bufmgr_gem.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/intel/intel_bufmgr_gem.c b/intel/intel_bufmgr_gem.c
> index f98f7a7..278f5c8 100644
> --- a/intel/intel_bufmgr_gem.c
> +++ b/intel/intel_bufmgr_gem.c
> @@ -2452,7 +2452,17 @@ drm_intel_bo_gem_create_from_prime(drm_intel_bufmgr *bufmgr, int prime_fd, int s
>  	if (!bo_gem)
>  		return NULL;
>  
> -	bo_gem->bo.size = size;
> +	/* Determine size of bo.  The fd-to-handle ioctl really should
> +	 * return the size, but it doesn't.  If we have kernel 3.12 or
> +	 * later, we can lseek on the prime fd to get the size.  Older
> +	 * kernels will just fail, in which case we fall back to the
> +	 * provided (estimated or guess size). */
> +	ret = lseek(prime_fd, 0, SEEK_END);
> +	if (ret != -1)
> +		bo_gem->bo.size = ret;
> +	else
> +		bo_gem->bo.size = size;
> +
>  	bo_gem->bo.handle = handle;
>  	bo_gem->bo.bufmgr = bufmgr;
>  
> -- 
> 1.8.3.1
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch