Drivers provide these callbacks......
struct drm_driver_fn {
u32 driver_features;
int dev_priv_size;
int permanent_maps;
drm_ioctl_desc_t *ioctls;
int num_ioctls;
int (*preinit)(struct drm_device *, unsigned long flags);
void (*prerelease)(struct drm_device *, struct file *filp);
void (*pretakedown)(struct drm_device *);
int (*postcleanup)(struct drm_device *);
int (*presetup)(struct drm_device *);
int (*postsetup)(struct drm_device *);
int (*dma_ioctl)( DRM_IOCTL_ARGS );
/* these are opposites at the moment */
int (*open_helper)(struct drm_device *, drm_file_t *);
void (*free_filp_priv)(struct drm_device *, drm_file_t *);
void (*release)(struct drm_device *, struct file *filp);
void (*dma_ready)(struct drm_device *);
int (*dma_quiescent)(struct drm_device *);
int (*context_ctor)(struct drm_device *dev, int context);
int (*context_dtor)(struct drm_device *dev, int context);
int (*kernel_context_switch)(struct drm_device *dev, int old, int new);
int (*kernel_context_switch_unlock)(struct drm_device *dev);
int (*vblank_wait)(struct drm_device *dev, unsigned int *sequence);
/* these have to be filled in */
int (*postinit)(struct drm_device *, unsigned long flags);
irqreturn_t (*irq_handler)( DRM_IRQ_ARGS );
void (*irq_preinstall)(struct drm_device *dev);
void (*irq_postinstall)(struct drm_device *dev);
void (*irq_uninstall)(struct drm_device *dev);
void (*reclaim_buffers)(struct file *filp);
unsigned long (*get_map_ofs)(drm_map_t *map);
unsigned long (*get_reg_ofs)(struct drm_device *dev);
void (*set_version)(struct drm_device *dev, drm_set_version_t *sv);
int (*version)(drm_version_t *version);
};