Re: [PATCH 6/9] drm/xen-front: Introduce DRM/KMS virtual display driver

On 02/21/2018 03:03 AM, Oleksandr Andrushchenko wrote:

+struct drm_driver xen_drm_driver = {

• .driver_features = DRIVER_GEM | DRIVER_MODESET |

• 		     DRIVER_PRIME | DRIVER_ATOMIC,
  

• .lastclose = lastclose,
• .gem_free_object_unlocked = free_object,
• .gem_vm_ops = &xen_drm_vm_ops,
• .prime_handle_to_fd = drm_gem_prime_handle_to_fd,
• .prime_fd_to_handle = drm_gem_prime_fd_to_handle,
• .gem_prime_import = drm_gem_prime_import,
• .gem_prime_export = drm_gem_prime_export,
• .gem_prime_get_sg_table = prime_get_sg_table,
• .gem_prime_import_sg_table = prime_import_sg_table,
• .gem_prime_vmap = prime_vmap,
• .gem_prime_vunmap = prime_vunmap,
• .gem_prime_mmap = prime_mmap,
• .dumb_create = dumb_create,
• .fops = &xendrm_fops,
• .name = "xendrm-du",
• .desc = "Xen PV DRM Display Unit",
• .date = "20161109",

You must have been working on this for a while ;-)

I assume this needs to be updated.

+bool xen_drm_front_drv_is_used(struct platform_device *pdev) +{

• struct xen_drm_front_drm_info *drm_info = platform_get_drvdata(pdev);
• struct drm_device *dev;
• if (!drm_info)

• return false;
  

• dev = drm_info->drm_dev;
• if (!dev)

• return false;
  

• /*

• * FIXME: the code below must be protected by drm_global_mutex,
  

• * but it is not accessible to us. Anyways there is a race condition,
  

• * but we will re-try.
  

• */
  

• return dev->open_count != 0;

Would it be a problem, given the race, if you report that the frontend is not in use, while it actually is?

-boris