drm_open
.open = drm_open,
.d_open = drm_open,
int drm_open(struct dev_open_args *ap)
EXPORT_SYMBOL(drm_open);
.open = drm_open,
d_open_t drm_open;
int drm_open(struct inode *inode, struct file *filp);
.open = drm_open,\
.open = drm_open,\
.open = drm_open,