include/drm/drm_fb_helper.h - arm/linux - Git at Google

 /*
  * Copyright (c) 2006-2009 Red Hat Inc.
  * Copyright (c) 2006-2008 Intel Corporation
  * Copyright (c) 2007 Dave Airlie <airlied@linux.ie>
  *
  * DRM framebuffer helper functions
  *
  * Permission to use, copy, modify, distribute, and sell this software and its
  * documentation for any purpose is hereby granted without fee, provided that
  * the above copyright notice appear in all copies and that both that copyright
  * notice and this permission notice appear in supporting documentation, and
  * that the name of the copyright holders not be used in advertising or
  * publicity pertaining to distribution of the software without specific,
  * written prior permission.  The copyright holders make no representations
  * about the suitability of this software for any purpose.  It is provided "as
  * is" without express or implied warranty.
  *
  * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
  * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
  * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
  * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
  * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
  * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
  * OF THIS SOFTWARE.
  *
  * Authors:
  *      Dave Airlie <airlied@linux.ie>
  *      Jesse Barnes <jesse.barnes@intel.com>
  */
 #ifndef DRM_FB_HELPER_H
 #define DRM_FB_HELPER_H

 struct drm_fb_helper;

 #include <drm/drm_crtc.h>
 #include <linux/kgdb.h>

 enum mode_set_atomic {
 	LEAVE_ATOMIC_MODE_SET,
 	ENTER_ATOMIC_MODE_SET,
 };

 struct drm_fb_offset {
 	int x, y;
 };

 struct drm_fb_helper_crtc {
 	struct drm_mode_set mode_set;
 	struct drm_display_mode *desired_mode;
 	int x, y;
 };

 /**
  * struct drm_fb_helper_surface_size - describes fbdev size and scanout surface size
  * @fb_width: fbdev width
  * @fb_height: fbdev height
  * @surface_width: scanout buffer width
  * @surface_height: scanout buffer height
  * @surface_bpp: scanout buffer bpp
  * @surface_depth: scanout buffer depth
  *
  * Note that the scanout surface width/height may be larger than the fbdev
  * width/height.  In case of multiple displays, the scanout surface is sized
  * according to the largest width/height (so it is large enough for all CRTCs
  * to scanout).  But the fbdev width/height is sized to the minimum width/
  * height of all the displays.  This ensures that fbcon fits on the smallest
  * of the attached displays.
  *
  * So what is passed to drm_fb_helper_fill_var() should be fb_width/fb_height,
  * rather than the surface size.
  */
 struct drm_fb_helper_surface_size {
 	u32 fb_width;
 	u32 fb_height;
 	u32 surface_width;
 	u32 surface_height;
 	u32 surface_bpp;
 	u32 surface_depth;
 };

 /**
  * struct drm_fb_helper_funcs - driver callbacks for the fbdev emulation library
  *
  * Driver callbacks used by the fbdev emulation helper library.
  */
 struct drm_fb_helper_funcs {
 	/**
 	 * @fb_probe:
 	 *
 	 * Driver callback to allocate and initialize the fbdev info structure.
 	 * Furthermore it also needs to allocate the DRM framebuffer used to
 	 * back the fbdev.
 	 *
 	 * This callback is mandatory.
 	 *
 	 * RETURNS:
 	 *
 	 * The driver should return 0 on success and a negative error code on
 	 * failure.
 	 */
 	int (*fb_probe)(struct drm_fb_helper *helper,
 			struct drm_fb_helper_surface_size *sizes);

 	/**
 	 * @initial_config:
 	 *
 	 * Driver callback to setup an initial fbdev display configuration.
 	 * Drivers can use this callback to tell the fbdev emulation what the
 	 * preferred initial configuration is. This is useful to implement
 	 * smooth booting where the fbdev (and subsequently all userspace) never
 	 * changes the mode, but always inherits the existing configuration.
 	 *
 	 * This callback is optional.
 	 *
 	 * RETURNS:
 	 *
 	 * The driver should return true if a suitable initial configuration has
 	 * been filled out and false when the fbdev helper should fall back to
 	 * the default probing logic.
 	 */
 	bool (*initial_config)(struct drm_fb_helper *fb_helper,
 			       struct drm_fb_helper_crtc **crtcs,
 			       struct drm_display_mode **modes,
 			       struct drm_fb_offset *offsets,
 			       bool *enabled, int width, int height);
 };

 struct drm_fb_helper_connector {
 	struct drm_connector *connector;
 };

 /**
  * struct drm_fb_helper - main structure to emulate fbdev on top of KMS
  * @fb: Scanout framebuffer object
  * @dev: DRM device
  * @crtc_count: number of possible CRTCs
  * @crtc_info: per-CRTC helper state (mode, x/y offset, etc)
  * @connector_count: number of connected connectors
  * @connector_info_alloc_count: size of connector_info
  * @funcs: driver callbacks for fb helper
  * @fbdev: emulated fbdev device info struct
  * @pseudo_palette: fake palette of 16 colors
  * @dirty_clip: clip rectangle used with deferred_io to accumulate damage to
  *              the screen buffer
  * @dirty_lock: spinlock protecting @dirty_clip
  * @dirty_work: worker used to flush the framebuffer
  * @resume_work: worker used during resume if the console lock is already taken
  *
  * This is the main structure used by the fbdev helpers. Drivers supporting
  * fbdev emulation should embedded this into their overall driver structure.
  * Drivers must also fill out a &struct drm_fb_helper_funcs with a few
  * operations.
  */
 struct drm_fb_helper {
 	struct drm_framebuffer *fb;
 	struct drm_device *dev;
 	int crtc_count;
 	struct drm_fb_helper_crtc *crtc_info;
 	int connector_count;
 	int connector_info_alloc_count;
 	/**
 	 * @connector_info:
 	 *
 	 * Array of per-connector information. Do not iterate directly, but use
 	 * drm_fb_helper_for_each_connector.
 	 */
 	struct drm_fb_helper_connector **connector_info;
 	const struct drm_fb_helper_funcs *funcs;
 	struct fb_info *fbdev;
 	u32 pseudo_palette[17];
 	struct drm_clip_rect dirty_clip;
 	spinlock_t dirty_lock;
 	struct work_struct dirty_work;
 	struct work_struct resume_work;

 	/**
 	 * @lock:
 	 *
 	 * Top-level FBDEV helper lock. This protects all internal data
 	 * structures and lists, such as @connector_info and @crtc_info.
 	 *
 	 * FIXME: fbdev emulation locking is a mess and long term we want to
 	 * protect all helper internal state with this lock as well as reduce
 	 * core KMS locking as much as possible.
 	 */
 	struct mutex lock;

 	/**
 	 * @kernel_fb_list:
 	 *
 	 * Entry on the global kernel_fb_helper_list, used for kgdb entry/exit.
 	 */
 	struct list_head kernel_fb_list;

 	/**
 	 * @delayed_hotplug:
 	 *
 	 * A hotplug was received while fbdev wasn't in control of the DRM
 	 * device, i.e. another KMS master was active. The output configuration
 	 * needs to be reprobe when fbdev is in control again.
 	 */
 	bool delayed_hotplug;

 	/**
 	 * @deferred_setup:
 	 *
 	 * If no outputs are connected (disconnected or unknown) the FB helper
 	 * code will defer setup until at least one of the outputs shows up.
 	 * This field keeps track of the status so that setup can be retried
 	 * at every hotplug event until it succeeds eventually.
 	 *
 	 * Protected by @lock.
 	 */
 	bool deferred_setup;

 	/**
 	 * @preferred_bpp:
 	 *
 	 * Temporary storage for the driver's preferred BPP setting passed to
 	 * FB helper initialization. This needs to be tracked so that deferred
 	 * FB helper setup can pass this on.
 	 *
 	 * See also: @deferred_setup
 	 */
 	int preferred_bpp;
 };

 /**
  * define DRM_FB_HELPER_DEFAULT_OPS - helper define for drm drivers
  *
  * Helper define to register default implementations of drm_fb_helper
  * functions. To be used in struct fb_ops of drm drivers.
  */
 #define DRM_FB_HELPER_DEFAULT_OPS \
 	.fb_check_var	= drm_fb_helper_check_var, \
 	.fb_set_par	= drm_fb_helper_set_par, \
 	.fb_setcmap	= drm_fb_helper_setcmap, \
 	.fb_blank	= drm_fb_helper_blank, \
 	.fb_pan_display	= drm_fb_helper_pan_display, \
 	.fb_debug_enter = drm_fb_helper_debug_enter, \
 	.fb_debug_leave = drm_fb_helper_debug_leave, \
 	.fb_ioctl	= drm_fb_helper_ioctl

 #ifdef CONFIG_DRM_FBDEV_EMULATION
 void drm_fb_helper_prepare(struct drm_device *dev, struct drm_fb_helper *helper,
 			   const struct drm_fb_helper_funcs *funcs);
 int drm_fb_helper_init(struct drm_device *dev,
 		       struct drm_fb_helper *helper, int max_conn);
 void drm_fb_helper_fini(struct drm_fb_helper *helper);
 int drm_fb_helper_blank(int blank, struct fb_info *info);
 int drm_fb_helper_pan_display(struct fb_var_screeninfo *var,
 			      struct fb_info *info);
 int drm_fb_helper_set_par(struct fb_info *info);
 int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
 			    struct fb_info *info);

 int drm_fb_helper_restore_fbdev_mode_unlocked(struct drm_fb_helper *fb_helper);

 struct fb_info *drm_fb_helper_alloc_fbi(struct drm_fb_helper *fb_helper);
 void drm_fb_helper_unregister_fbi(struct drm_fb_helper *fb_helper);
 void drm_fb_helper_fill_var(struct fb_info *info, struct drm_fb_helper *fb_helper,
 			    uint32_t fb_width, uint32_t fb_height);
 void drm_fb_helper_fill_fix(struct fb_info *info, uint32_t pitch,
 			    uint32_t depth);

 void drm_fb_helper_unlink_fbi(struct drm_fb_helper *fb_helper);

 void drm_fb_helper_deferred_io(struct fb_info *info,
 			       struct list_head *pagelist);

 ssize_t drm_fb_helper_sys_read(struct fb_info *info, char __user *buf,
 			       size_t count, loff_t *ppos);
 ssize_t drm_fb_helper_sys_write(struct fb_info *info, const char __user *buf,
 				size_t count, loff_t *ppos);

 void drm_fb_helper_sys_fillrect(struct fb_info *info,
 				const struct fb_fillrect *rect);
 void drm_fb_helper_sys_copyarea(struct fb_info *info,
 				const struct fb_copyarea *area);
 void drm_fb_helper_sys_imageblit(struct fb_info *info,
 				 const struct fb_image *image);

 void drm_fb_helper_cfb_fillrect(struct fb_info *info,
 				const struct fb_fillrect *rect);
 void drm_fb_helper_cfb_copyarea(struct fb_info *info,
 				const struct fb_copyarea *area);
 void drm_fb_helper_cfb_imageblit(struct fb_info *info,
 				 const struct fb_image *image);

 void drm_fb_helper_set_suspend(struct drm_fb_helper *fb_helper, bool suspend);
 void drm_fb_helper_set_suspend_unlocked(struct drm_fb_helper *fb_helper,
 					bool suspend);

 int drm_fb_helper_setcmap(struct fb_cmap *cmap, struct fb_info *info);

 int drm_fb_helper_ioctl(struct fb_info *info, unsigned int cmd,
 			unsigned long arg);

 int drm_fb_helper_hotplug_event(struct drm_fb_helper *fb_helper);
 int drm_fb_helper_initial_config(struct drm_fb_helper *fb_helper, int bpp_sel);
 int drm_fb_helper_single_add_all_connectors(struct drm_fb_helper *fb_helper);
 int drm_fb_helper_debug_enter(struct fb_info *info);
 int drm_fb_helper_debug_leave(struct fb_info *info);
 struct drm_display_mode *
 drm_has_preferred_mode(struct drm_fb_helper_connector *fb_connector,
 			int width, int height);
 struct drm_display_mode *
 drm_pick_cmdline_mode(struct drm_fb_helper_connector *fb_helper_conn);

 int drm_fb_helper_add_one_connector(struct drm_fb_helper *fb_helper, struct drm_connector *connector);
 int drm_fb_helper_remove_one_connector(struct drm_fb_helper *fb_helper,
 				       struct drm_connector *connector);
 #else
 static inline void drm_fb_helper_prepare(struct drm_device *dev,
 					struct drm_fb_helper *helper,
 					const struct drm_fb_helper_funcs *funcs)
 {
 }

 static inline int drm_fb_helper_init(struct drm_device *dev,
 		       struct drm_fb_helper *helper,
 		       int max_conn)
 {
 	return 0;
 }

 static inline void drm_fb_helper_fini(struct drm_fb_helper *helper)
 {
 }

 static inline int drm_fb_helper_blank(int blank, struct fb_info *info)
 {
 	return 0;
 }

 static inline int drm_fb_helper_pan_display(struct fb_var_screeninfo *var,
 					    struct fb_info *info)
 {
 	return 0;
 }

 static inline int drm_fb_helper_set_par(struct fb_info *info)
 {
 	return 0;
 }

 static inline int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
 					  struct fb_info *info)
 {
 	return 0;
 }

 static inline int
 drm_fb_helper_restore_fbdev_mode_unlocked(struct drm_fb_helper *fb_helper)
 {
 	return 0;
 }

 static inline struct fb_info *
 drm_fb_helper_alloc_fbi(struct drm_fb_helper *fb_helper)
 {
 	return NULL;
 }

 static inline void drm_fb_helper_unregister_fbi(struct drm_fb_helper *fb_helper)
 {
 }

 static inline void drm_fb_helper_fill_var(struct fb_info *info,
 					  struct drm_fb_helper *fb_helper,
 					  uint32_t fb_width, uint32_t fb_height)
 {
 }

 static inline void drm_fb_helper_fill_fix(struct fb_info *info, uint32_t pitch,
 					  uint32_t depth)
 {
 }

 static inline int drm_fb_helper_setcmap(struct fb_cmap *cmap,
 					struct fb_info *info)
 {
 	return 0;
 }

 static inline int drm_fb_helper_ioctl(struct fb_info *info, unsigned int cmd,
 				      unsigned long arg)
 {
 	return 0;
 }

 static inline void drm_fb_helper_unlink_fbi(struct drm_fb_helper *fb_helper)
 {
 }

 static inline void drm_fb_helper_deferred_io(struct fb_info *info,
 					     struct list_head *pagelist)
 {
 }

 static inline ssize_t drm_fb_helper_sys_read(struct fb_info *info,
 					     char __user *buf, size_t count,
 					     loff_t *ppos)
 {
 	return -ENODEV;
 }

 static inline ssize_t drm_fb_helper_sys_write(struct fb_info *info,
 					      const char __user *buf,
 					      size_t count, loff_t *ppos)
 {
 	return -ENODEV;
 }

 static inline void drm_fb_helper_sys_fillrect(struct fb_info *info,
 					      const struct fb_fillrect *rect)
 {
 }

 static inline void drm_fb_helper_sys_copyarea(struct fb_info *info,
 					      const struct fb_copyarea *area)
 {
 }

 static inline void drm_fb_helper_sys_imageblit(struct fb_info *info,
 					       const struct fb_image *image)
 {
 }

 static inline void drm_fb_helper_cfb_fillrect(struct fb_info *info,
 					      const struct fb_fillrect *rect)
 {
 }

 static inline void drm_fb_helper_cfb_copyarea(struct fb_info *info,
 					      const struct fb_copyarea *area)
 {
 }

 static inline void drm_fb_helper_cfb_imageblit(struct fb_info *info,
 					       const struct fb_image *image)
 {
 }

 static inline void drm_fb_helper_set_suspend(struct drm_fb_helper *fb_helper,
 					     bool suspend)
 {
 }

 static inline void
 drm_fb_helper_set_suspend_unlocked(struct drm_fb_helper *fb_helper, bool suspend)
 {
 }

 static inline int drm_fb_helper_hotplug_event(struct drm_fb_helper *fb_helper)
 {
 	return 0;
 }

 static inline int drm_fb_helper_initial_config(struct drm_fb_helper *fb_helper,
 					       int bpp_sel)
 {
 	return 0;
 }

 static inline int
 drm_fb_helper_single_add_all_connectors(struct drm_fb_helper *fb_helper)
 {
 	return 0;
 }

 static inline int drm_fb_helper_debug_enter(struct fb_info *info)
 {
 	return 0;
 }

 static inline int drm_fb_helper_debug_leave(struct fb_info *info)
 {
 	return 0;
 }

 static inline struct drm_display_mode *
 drm_has_preferred_mode(struct drm_fb_helper_connector *fb_connector,
 		       int width, int height)
 {
 	return NULL;
 }

 static inline struct drm_display_mode *
 drm_pick_cmdline_mode(struct drm_fb_helper_connector *fb_helper_conn,
 		      int width, int height)
 {
 	return NULL;
 }

 static inline int
 drm_fb_helper_add_one_connector(struct drm_fb_helper *fb_helper,
 				struct drm_connector *connector)
 {
 	return 0;
 }

 static inline int
 drm_fb_helper_remove_one_connector(struct drm_fb_helper *fb_helper,
 				   struct drm_connector *connector)
 {
 	return 0;
 }

 #endif

 static inline int
 drm_fb_helper_remove_conflicting_framebuffers(struct apertures_struct *a,
 					      const char *name, bool primary)
 {
 #if IS_REACHABLE(CONFIG_FB)
 	return remove_conflicting_framebuffers(a, name, primary);
 #else
 	return 0;
 #endif
 }

 #endif
	/*
	* Copyright (c) 2006-2009 Red Hat Inc.
	* Copyright (c) 2006-2008 Intel Corporation
	* Copyright (c) 2007 Dave Airlie <airlied@linux.ie>
	*
	* DRM framebuffer helper functions
	*
	* Permission to use, copy, modify, distribute, and sell this software and its
	* documentation for any purpose is hereby granted without fee, provided that
	* the above copyright notice appear in all copies and that both that copyright
	* notice and this permission notice appear in supporting documentation, and
	* that the name of the copyright holders not be used in advertising or
	* publicity pertaining to distribution of the software without specific,
	* written prior permission. The copyright holders make no representations
	* about the suitability of this software for any purpose. It is provided "as
	* is" without express or implied warranty.
	*
	* THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
	* INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
	* EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
	* CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
	* DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
	* TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
	* OF THIS SOFTWARE.
	*
	* Authors:
	* Dave Airlie <airlied@linux.ie>
	* Jesse Barnes <jesse.barnes@intel.com>
	*/
	#ifndef DRM_FB_HELPER_H
	#define DRM_FB_HELPER_H

	struct drm_fb_helper;

	#include <drm/drm_crtc.h>
	#include <linux/kgdb.h>

	enum mode_set_atomic {
	LEAVE_ATOMIC_MODE_SET,
	ENTER_ATOMIC_MODE_SET,
	};

	struct drm_fb_offset {
	int x, y;
	};

	struct drm_fb_helper_crtc {
	struct drm_mode_set mode_set;
	struct drm_display_mode *desired_mode;
	int x, y;
	};

	/**
	* struct drm_fb_helper_surface_size - describes fbdev size and scanout surface size
	* @fb_width: fbdev width
	* @fb_height: fbdev height
	* @surface_width: scanout buffer width
	* @surface_height: scanout buffer height
	* @surface_bpp: scanout buffer bpp
	* @surface_depth: scanout buffer depth
	*
	* Note that the scanout surface width/height may be larger than the fbdev
	* width/height. In case of multiple displays, the scanout surface is sized
	* according to the largest width/height (so it is large enough for all CRTCs
	* to scanout). But the fbdev width/height is sized to the minimum width/
	* height of all the displays. This ensures that fbcon fits on the smallest
	* of the attached displays.
	*
	* So what is passed to drm_fb_helper_fill_var() should be fb_width/fb_height,
	* rather than the surface size.
	*/
	struct drm_fb_helper_surface_size {
	u32 fb_width;
	u32 fb_height;
	u32 surface_width;
	u32 surface_height;
	u32 surface_bpp;
	u32 surface_depth;
	};

	/**
	* struct drm_fb_helper_funcs - driver callbacks for the fbdev emulation library
	*
	* Driver callbacks used by the fbdev emulation helper library.
	*/
	struct drm_fb_helper_funcs {
	/**
	* @fb_probe:
	*
	* Driver callback to allocate and initialize the fbdev info structure.
	* Furthermore it also needs to allocate the DRM framebuffer used to
	* back the fbdev.
	*
	* This callback is mandatory.
	*
	* RETURNS:
	*
	* The driver should return 0 on success and a negative error code on
	* failure.
	*/
	int (fb_probe)(struct drm_fb_helper helper,
	struct drm_fb_helper_surface_size *sizes);

	/**
	* @initial_config:
	*
	* Driver callback to setup an initial fbdev display configuration.
	* Drivers can use this callback to tell the fbdev emulation what the
	* preferred initial configuration is. This is useful to implement
	* smooth booting where the fbdev (and subsequently all userspace) never
	* changes the mode, but always inherits the existing configuration.
	*
	* This callback is optional.
	*
	* RETURNS:
	*
	* The driver should return true if a suitable initial configuration has
	* been filled out and false when the fbdev helper should fall back to
	* the default probing logic.
	*/
	bool (initial_config)(struct drm_fb_helper fb_helper,
	struct drm_fb_helper_crtc **crtcs,
	struct drm_display_mode **modes,
	struct drm_fb_offset *offsets,
	bool *enabled, int width, int height);
	};

	struct drm_fb_helper_connector {
	struct drm_connector *connector;
	};

	/**
	* struct drm_fb_helper - main structure to emulate fbdev on top of KMS
	* @fb: Scanout framebuffer object
	* @dev: DRM device
	* @crtc_count: number of possible CRTCs
	* @crtc_info: per-CRTC helper state (mode, x/y offset, etc)
	* @connector_count: number of connected connectors
	* @connector_info_alloc_count: size of connector_info
	* @funcs: driver callbacks for fb helper
	* @fbdev: emulated fbdev device info struct
	* @pseudo_palette: fake palette of 16 colors
	* @dirty_clip: clip rectangle used with deferred_io to accumulate damage to
	* the screen buffer
	* @dirty_lock: spinlock protecting @dirty_clip
	* @dirty_work: worker used to flush the framebuffer
	* @resume_work: worker used during resume if the console lock is already taken
	*
	* This is the main structure used by the fbdev helpers. Drivers supporting
	* fbdev emulation should embedded this into their overall driver structure.
	* Drivers must also fill out a &struct drm_fb_helper_funcs with a few
	* operations.
	*/
	struct drm_fb_helper {
	struct drm_framebuffer *fb;
	struct drm_device *dev;
	int crtc_count;
	struct drm_fb_helper_crtc *crtc_info;
	int connector_count;
	int connector_info_alloc_count;
	/**
	* @connector_info:
	*
	* Array of per-connector information. Do not iterate directly, but use
	* drm_fb_helper_for_each_connector.
	*/
	struct drm_fb_helper_connector **connector_info;
	const struct drm_fb_helper_funcs *funcs;
	struct fb_info *fbdev;
	u32 pseudo_palette[17];
	struct drm_clip_rect dirty_clip;
	spinlock_t dirty_lock;
	struct work_struct dirty_work;
	struct work_struct resume_work;

	/**
	* @lock:
	*
	* Top-level FBDEV helper lock. This protects all internal data
	* structures and lists, such as @connector_info and @crtc_info.
	*
	* FIXME: fbdev emulation locking is a mess and long term we want to
	* protect all helper internal state with this lock as well as reduce
	* core KMS locking as much as possible.
	*/
	struct mutex lock;

	/**
	* @kernel_fb_list:
	*
	* Entry on the global kernel_fb_helper_list, used for kgdb entry/exit.
	*/
	struct list_head kernel_fb_list;

	/**
	* @delayed_hotplug:
	*
	* A hotplug was received while fbdev wasn't in control of the DRM
	* device, i.e. another KMS master was active. The output configuration
	* needs to be reprobe when fbdev is in control again.
	*/
	bool delayed_hotplug;

	/**
	* @deferred_setup:
	*
	* If no outputs are connected (disconnected or unknown) the FB helper
	* code will defer setup until at least one of the outputs shows up.
	* This field keeps track of the status so that setup can be retried
	* at every hotplug event until it succeeds eventually.
	*
	* Protected by @lock.
	*/
	bool deferred_setup;

	/**
	* @preferred_bpp:
	*
	* Temporary storage for the driver's preferred BPP setting passed to
	* FB helper initialization. This needs to be tracked so that deferred
	* FB helper setup can pass this on.
	*
	* See also: @deferred_setup
	*/
	int preferred_bpp;
	};

	/**
	* define DRM_FB_HELPER_DEFAULT_OPS - helper define for drm drivers
	*
	* Helper define to register default implementations of drm_fb_helper
	* functions. To be used in struct fb_ops of drm drivers.
	*/
	#define DRM_FB_HELPER_DEFAULT_OPS \
	.fb_check_var = drm_fb_helper_check_var, \
	.fb_set_par = drm_fb_helper_set_par, \
	.fb_setcmap = drm_fb_helper_setcmap, \
	.fb_blank = drm_fb_helper_blank, \
	.fb_pan_display = drm_fb_helper_pan_display, \
	.fb_debug_enter = drm_fb_helper_debug_enter, \
	.fb_debug_leave = drm_fb_helper_debug_leave, \
	.fb_ioctl = drm_fb_helper_ioctl

	#ifdef CONFIG_DRM_FBDEV_EMULATION
	void drm_fb_helper_prepare(struct drm_device dev, struct drm_fb_helper helper,
	const struct drm_fb_helper_funcs *funcs);
	int drm_fb_helper_init(struct drm_device *dev,
	struct drm_fb_helper *helper, int max_conn);
	void drm_fb_helper_fini(struct drm_fb_helper *helper);
	int drm_fb_helper_blank(int blank, struct fb_info *info);
	int drm_fb_helper_pan_display(struct fb_var_screeninfo *var,
	struct fb_info *info);
	int drm_fb_helper_set_par(struct fb_info *info);
	int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
	struct fb_info *info);

	int drm_fb_helper_restore_fbdev_mode_unlocked(struct drm_fb_helper *fb_helper);

	struct fb_info drm_fb_helper_alloc_fbi(struct drm_fb_helper fb_helper);
	void drm_fb_helper_unregister_fbi(struct drm_fb_helper *fb_helper);
	void drm_fb_helper_fill_var(struct fb_info info, struct drm_fb_helper fb_helper,
	uint32_t fb_width, uint32_t fb_height);
	void drm_fb_helper_fill_fix(struct fb_info *info, uint32_t pitch,
	uint32_t depth);

	void drm_fb_helper_unlink_fbi(struct drm_fb_helper *fb_helper);

	void drm_fb_helper_deferred_io(struct fb_info *info,
	struct list_head *pagelist);

	ssize_t drm_fb_helper_sys_read(struct fb_info info, char __user buf,
	size_t count, loff_t *ppos);
	ssize_t drm_fb_helper_sys_write(struct fb_info info, const char __user buf,
	size_t count, loff_t *ppos);

	void drm_fb_helper_sys_fillrect(struct fb_info *info,
	const struct fb_fillrect *rect);
	void drm_fb_helper_sys_copyarea(struct fb_info *info,
	const struct fb_copyarea *area);
	void drm_fb_helper_sys_imageblit(struct fb_info *info,
	const struct fb_image *image);

	void drm_fb_helper_cfb_fillrect(struct fb_info *info,
	const struct fb_fillrect *rect);
	void drm_fb_helper_cfb_copyarea(struct fb_info *info,
	const struct fb_copyarea *area);
	void drm_fb_helper_cfb_imageblit(struct fb_info *info,
	const struct fb_image *image);

	void drm_fb_helper_set_suspend(struct drm_fb_helper *fb_helper, bool suspend);
	void drm_fb_helper_set_suspend_unlocked(struct drm_fb_helper *fb_helper,
	bool suspend);

	int drm_fb_helper_setcmap(struct fb_cmap cmap, struct fb_info info);

	int drm_fb_helper_ioctl(struct fb_info *info, unsigned int cmd,
	unsigned long arg);

	int drm_fb_helper_hotplug_event(struct drm_fb_helper *fb_helper);
	int drm_fb_helper_initial_config(struct drm_fb_helper *fb_helper, int bpp_sel);
	int drm_fb_helper_single_add_all_connectors(struct drm_fb_helper *fb_helper);
	int drm_fb_helper_debug_enter(struct fb_info *info);
	int drm_fb_helper_debug_leave(struct fb_info *info);
	struct drm_display_mode *
	drm_has_preferred_mode(struct drm_fb_helper_connector *fb_connector,
	int width, int height);
	struct drm_display_mode *
	drm_pick_cmdline_mode(struct drm_fb_helper_connector *fb_helper_conn);

	int drm_fb_helper_add_one_connector(struct drm_fb_helper fb_helper, struct drm_connector connector);
	int drm_fb_helper_remove_one_connector(struct drm_fb_helper *fb_helper,
	struct drm_connector *connector);
	#else
	static inline void drm_fb_helper_prepare(struct drm_device *dev,
	struct drm_fb_helper *helper,
	const struct drm_fb_helper_funcs *funcs)
	{
	}

	static inline int drm_fb_helper_init(struct drm_device *dev,
	struct drm_fb_helper *helper,
	int max_conn)
	{
	return 0;
	}

	static inline void drm_fb_helper_fini(struct drm_fb_helper *helper)
	{
	}

	static inline int drm_fb_helper_blank(int blank, struct fb_info *info)
	{
	return 0;
	}

	static inline int drm_fb_helper_pan_display(struct fb_var_screeninfo *var,
	struct fb_info *info)
	{
	return 0;
	}

	static inline int drm_fb_helper_set_par(struct fb_info *info)
	{
	return 0;
	}

	static inline int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
	struct fb_info *info)
	{
	return 0;
	}

	static inline int
	drm_fb_helper_restore_fbdev_mode_unlocked(struct drm_fb_helper *fb_helper)
	{
	return 0;
	}

	static inline struct fb_info *
	drm_fb_helper_alloc_fbi(struct drm_fb_helper *fb_helper)
	{
	return NULL;
	}

	static inline void drm_fb_helper_unregister_fbi(struct drm_fb_helper *fb_helper)
	{
	}

	static inline void drm_fb_helper_fill_var(struct fb_info *info,
	struct drm_fb_helper *fb_helper,
	uint32_t fb_width, uint32_t fb_height)
	{
	}

	static inline void drm_fb_helper_fill_fix(struct fb_info *info, uint32_t pitch,
	uint32_t depth)
	{
	}

	static inline int drm_fb_helper_setcmap(struct fb_cmap *cmap,
	struct fb_info *info)
	{
	return 0;
	}

	static inline int drm_fb_helper_ioctl(struct fb_info *info, unsigned int cmd,
	unsigned long arg)
	{
	return 0;
	}

	static inline void drm_fb_helper_unlink_fbi(struct drm_fb_helper *fb_helper)
	{
	}

	static inline void drm_fb_helper_deferred_io(struct fb_info *info,
	struct list_head *pagelist)
	{
	}

	static inline ssize_t drm_fb_helper_sys_read(struct fb_info *info,
	char __user *buf, size_t count,
	loff_t *ppos)
	{
	return -ENODEV;
	}

	static inline ssize_t drm_fb_helper_sys_write(struct fb_info *info,
	const char __user *buf,
	size_t count, loff_t *ppos)
	{
	return -ENODEV;
	}

	static inline void drm_fb_helper_sys_fillrect(struct fb_info *info,
	const struct fb_fillrect *rect)
	{
	}

	static inline void drm_fb_helper_sys_copyarea(struct fb_info *info,
	const struct fb_copyarea *area)
	{
	}

	static inline void drm_fb_helper_sys_imageblit(struct fb_info *info,
	const struct fb_image *image)
	{
	}

	static inline void drm_fb_helper_cfb_fillrect(struct fb_info *info,
	const struct fb_fillrect *rect)
	{
	}

	static inline void drm_fb_helper_cfb_copyarea(struct fb_info *info,
	const struct fb_copyarea *area)
	{
	}

	static inline void drm_fb_helper_cfb_imageblit(struct fb_info *info,
	const struct fb_image *image)
	{
	}

	static inline void drm_fb_helper_set_suspend(struct drm_fb_helper *fb_helper,
	bool suspend)
	{
	}

	static inline void
	drm_fb_helper_set_suspend_unlocked(struct drm_fb_helper *fb_helper, bool suspend)
	{
	}

	static inline int drm_fb_helper_hotplug_event(struct drm_fb_helper *fb_helper)
	{
	return 0;
	}

	static inline int drm_fb_helper_initial_config(struct drm_fb_helper *fb_helper,
	int bpp_sel)
	{
	return 0;
	}

	static inline int
	drm_fb_helper_single_add_all_connectors(struct drm_fb_helper *fb_helper)
	{
	return 0;
	}

	static inline int drm_fb_helper_debug_enter(struct fb_info *info)
	{
	return 0;
	}

	static inline int drm_fb_helper_debug_leave(struct fb_info *info)
	{
	return 0;
	}

	static inline struct drm_display_mode *
	drm_has_preferred_mode(struct drm_fb_helper_connector *fb_connector,
	int width, int height)
	{
	return NULL;
	}

	static inline struct drm_display_mode *
	drm_pick_cmdline_mode(struct drm_fb_helper_connector *fb_helper_conn,
	int width, int height)
	{
	return NULL;
	}

	static inline int
	drm_fb_helper_add_one_connector(struct drm_fb_helper *fb_helper,
	struct drm_connector *connector)
	{
	return 0;
	}

	static inline int
	drm_fb_helper_remove_one_connector(struct drm_fb_helper *fb_helper,
	struct drm_connector *connector)
	{
	return 0;
	}

	#endif

	static inline int
	drm_fb_helper_remove_conflicting_framebuffers(struct apertures_struct *a,
	const char *name, bool primary)
	{
	#if IS_REACHABLE(CONFIG_FB)
	return remove_conflicting_framebuffers(a, name, primary);
	#else
	return 0;
	#endif
	}

	#endif