Re: [PATCH 2/3] drm/vgem: Enable dmabuf interface for export

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, Jul 11, 2016 at 02:08:07PM +0100, Chris Wilson wrote:
> Enable the standard GEM dma-buf interface provided by the DRM core, but
> only for exporting the VGEM object. This allows passing around the VGEM
> objects created from the dumb interface and using them as sources
> elsewhere. Creating a VGEM object for a foriegn handle is not supported.
> 
> v2: With additional completeness.
> v3: Need to clear the CPU cache upon exporting the dma-addresses.
> v4: Use drm_gem_put_pages() as well.
> v5: Use drm_prime_pages_to_sg()
> 
> Testcase: igt/vgem_basic/dmabuf-*
> Testcase: igt/prime_vgem
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Sean Paul <seanpaul@chromium.org>
> Cc: Zach Reizner <zachr@google.com>
> Acked-by: Zach Reizner <zachr@google.com>
> Reviewed-by: Matthew Auld <matthew.auld@intel.com>

Merged the first 2 patches from this series.
-Daniel

> ---
>  drivers/gpu/drm/vgem/vgem_drv.c | 89 ++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 88 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/vgem/vgem_drv.c b/drivers/gpu/drm/vgem/vgem_drv.c
> index c161b6d7e427..b5fb968d2d5c 100644
> --- a/drivers/gpu/drm/vgem/vgem_drv.c
> +++ b/drivers/gpu/drm/vgem/vgem_drv.c
> @@ -192,14 +192,101 @@ static const struct file_operations vgem_driver_fops = {
>  	.release	= drm_release,
>  };
>  
> +static int vgem_prime_pin(struct drm_gem_object *obj)
> +{
> +	long n_pages = obj->size >> PAGE_SHIFT;
> +	struct page **pages;
> +
> +	/* Flush the object from the CPU cache so that importers can rely
> +	 * on coherent indirect access via the exported dma-address.
> +	 */
> +	pages = drm_gem_get_pages(obj);
> +	if (IS_ERR(pages))
> +		return PTR_ERR(pages);
> +
> +	drm_clflush_pages(pages, n_pages);
> +	drm_gem_put_pages(obj, pages, true, false);
> +
> +	return 0;
> +}
> +
> +static struct sg_table *vgem_prime_get_sg_table(struct drm_gem_object *obj)
> +{
> +	struct sg_table *st;
> +	struct page **pages;
> +
> +	pages = drm_gem_get_pages(obj);
> +	if (IS_ERR(pages))
> +		return ERR_CAST(pages);
> +
> +	st = drm_prime_pages_to_sg(pages, obj->size >> PAGE_SHIFT);
> +	drm_gem_put_pages(obj, pages, false, false);
> +
> +	return st;
> +}
> +
> +static void *vgem_prime_vmap(struct drm_gem_object *obj)
> +{
> +	long n_pages = obj->size >> PAGE_SHIFT;
> +	struct page **pages;
> +	void *addr;
> +
> +	pages = drm_gem_get_pages(obj);
> +	if (IS_ERR(pages))
> +		return NULL;
> +
> +	addr = vmap(pages, n_pages, 0, pgprot_writecombine(PAGE_KERNEL_IO));
> +	drm_gem_put_pages(obj, pages, false, false);
> +
> +	return addr;
> +}
> +
> +static void vgem_prime_vunmap(struct drm_gem_object *obj, void *vaddr)
> +{
> +	vunmap(vaddr);
> +}
> +
> +static int vgem_prime_mmap(struct drm_gem_object *obj,
> +			   struct vm_area_struct *vma)
> +{
> +	int ret;
> +
> +	if (obj->size < vma->vm_end - vma->vm_start)
> +		return -EINVAL;
> +
> +	if (!obj->filp)
> +		return -ENODEV;
> +
> +	ret = obj->filp->f_op->mmap(obj->filp, vma);
> +	if (ret)
> +		return ret;
> +
> +	fput(vma->vm_file);
> +	vma->vm_file = get_file(obj->filp);
> +	vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
> +	vma->vm_page_prot = pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
> +
> +	return 0;
> +}
> +
>  static struct drm_driver vgem_driver = {
> -	.driver_features		= DRIVER_GEM,
> +	.driver_features		= DRIVER_GEM | DRIVER_PRIME,
>  	.gem_free_object_unlocked	= vgem_gem_free_object,
>  	.gem_vm_ops			= &vgem_gem_vm_ops,
>  	.ioctls				= vgem_ioctls,
>  	.fops				= &vgem_driver_fops,
> +
>  	.dumb_create			= vgem_gem_dumb_create,
>  	.dumb_map_offset		= vgem_gem_dumb_map,
> +
> +	.prime_handle_to_fd = drm_gem_prime_handle_to_fd,
> +	.gem_prime_pin = vgem_prime_pin,
> +	.gem_prime_export = drm_gem_prime_export,
> +	.gem_prime_get_sg_table = vgem_prime_get_sg_table,
> +	.gem_prime_vmap = vgem_prime_vmap,
> +	.gem_prime_vunmap = vgem_prime_vunmap,
> +	.gem_prime_mmap = vgem_prime_mmap,
> +
>  	.name	= DRIVER_NAME,
>  	.desc	= DRIVER_DESC,
>  	.date	= DRIVER_DATE,
> -- 
> 2.8.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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