[Intel-gfx] [PATCH v3] drm/i915: Implement dma-buf mmap() for userspace access

[Chris Wilson]

On Thu, Jun 19, 2014 at 03:34:34PM +0300, Ander Conselvan de Oliveira wrote:
> From: Rob Bradford <rob at linux.intel.com>
> 
> The aim is that this is functionally equivalent to using the
> I915_GEM_MMAP ioctl.
> 
> v2: Add aperture check limit, limit to SNB+ and improve error handling.
> 
> v3 (anderco): Map without using the GTT.
> 
> Signed-off-by: Rob Bradford <rob at linux.intel.com>
> Signed-off-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira at intel.com>
> ---
>  drivers/gpu/drm/i915/i915_gem_dmabuf.c | 19 ++++++++++++++++++-
>  1 file changed, 18 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
> index 580aa42..2d31fca 100644
> --- a/drivers/gpu/drm/i915/i915_gem_dmabuf.c
> +++ b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
> @@ -193,7 +193,24 @@ static void i915_gem_dmabuf_kunmap(struct dma_buf *dma_buf, unsigned long page_n
>  
>  static int i915_gem_dmabuf_mmap(struct dma_buf *dma_buf, struct vm_area_struct *vma)
>  {
> -	return -EINVAL;
> +	struct drm_i915_gem_object *obj = dma_buf_to_obj(dma_buf);
> +	struct drm_device *dev = obj->base.dev;
> +	struct drm_i915_private *dev_priv = dev->dev_private;
> +	int ret;
> +
> +	if (INTEL_INFO(dev)->gen < 6)
> +		return -EINVAL;

For cpu mmapings, the check can die.
> +
> +	ret = i915_mutex_lock_interruptible(dev);
> +	if (ret)
> +		return ret;

This lock doesn't actually do anything useful.

obj->base.filp can be NULL.

> +
> +	ret = obj->base.filp->f_op->mmap(obj->base.filp, vma);
> +	fput(vma->vm_file);
> +	vma->vm_file = get_file(obj->base.filp);

Talk to me about how the user is expected to control coherency since
that appears to be outside of the scope of this function.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre