int drm_wait_vblank ( DRM_IOCTL_ARGS);
\param inode device inode. \param filp file pointer. \param cmd command. \param data user argument, pointing to a drm_wait_vblank structure. \return zero on success or a negative number on failure.
Verifies the IRQ is installed.
If a signal is requested checks if this task has already scheduled the same signal for the same vblank sequence number - nothing to be done in that case. If the number of tasks waiting for the interrupt exceeds 100 the function fails. Otherwise adds a new entry to drm_device::vbl_sigs for this task.
If a signal is not requested, then calls vblank_wait.