/*
   * Copyright (C) 2014 Red Hat
   * Author: Rob Clark <robdclark@gmail.com>
   *
   * Permission is hereby granted, free of charge, to any person obtaining a
   * copy of this software and associated documentation files (the "Software"),
   * to deal in the Software without restriction, including without limitation
   * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   * and/or sell copies of the Software, and to permit persons to whom the
   * Software is furnished to do so, subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in
   * all copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
   * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
   * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
   * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
   * OTHER DEALINGS IN THE SOFTWARE.
   */
  
  #ifndef DRM_MODESET_LOCK_H_
  #define DRM_MODESET_LOCK_H_
  
  #include <linux/ww_mutex.h>
  
  struct drm_modeset_lock;
  
  /**

   * struct drm_modeset_acquire_ctx - locking context (see ww_acquire_ctx)

   * @ww_ctx: base acquire ctx
   * @contended: used internally for -EDEADLK handling
   * @locked: list of held locks

   * @trylock_only: trylock mode used in atomic contexts/panic notifiers

   * @interruptible: whether interruptible locking should be used.

   *
   * Each thread competing for a set of locks must use one acquire
   * ctx.  And if any lock fxn returns -EDEADLK, it must backoff and
   * retry.
   */
  struct drm_modeset_acquire_ctx {
  
  	struct ww_acquire_ctx ww_ctx;

  	/*

  	 * Contended lock: if a lock is contended you should only call
  	 * drm_modeset_backoff() which drops locks and slow-locks the
  	 * contended lock.
  	 */
  	struct drm_modeset_lock *contended;

  	/*

  	 * list of held locks (drm_modeset_lock)
  	 */
  	struct list_head locked;

  	/*

  	 * Trylock mode, use only for panic handlers!
  	 */
  	bool trylock_only;

  
  	/* Perform interruptible waits on this context. */
  	bool interruptible;

  };
  
  /**

   * struct drm_modeset_lock - used for locking modeset resources.

   * @mutex: resource locking

   * @head: used to hold its place on &drm_atomi_state.locked list when

   *    part of an atomic update
   *
   * Used for locking CRTCs and other modeset resources.
   */
  struct drm_modeset_lock {

  	/*

  	 * modeset lock
  	 */
  	struct ww_mutex mutex;

  	/*

  	 * Resources that are locked as part of an atomic update are added
  	 * to a list (so we know what to unlock at the end).
  	 */
  	struct list_head head;
  };

  #define DRM_MODESET_ACQUIRE_INTERRUPTIBLE BIT(0)

  void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx,
  		uint32_t flags);
  void drm_modeset_acquire_fini(struct drm_modeset_acquire_ctx *ctx);
  void drm_modeset_drop_locks(struct drm_modeset_acquire_ctx *ctx);

  int drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx);

  void drm_modeset_lock_init(struct drm_modeset_lock *lock);

  
  /**
   * drm_modeset_lock_fini - cleanup lock
   * @lock: lock to cleanup
   */
  static inline void drm_modeset_lock_fini(struct drm_modeset_lock *lock)
  {
  	WARN_ON(!list_empty(&lock->head));
  }
  
  /**
   * drm_modeset_is_locked - equivalent to mutex_is_locked()
   * @lock: lock to check
   */
  static inline bool drm_modeset_is_locked(struct drm_modeset_lock *lock)
  {
  	return ww_mutex_is_locked(&lock->mutex);
  }
  
  int drm_modeset_lock(struct drm_modeset_lock *lock,
  		struct drm_modeset_acquire_ctx *ctx);

  int __must_check drm_modeset_lock_single_interruptible(struct drm_modeset_lock *lock);

  void drm_modeset_unlock(struct drm_modeset_lock *lock);
  
  struct drm_device;

  struct drm_crtc;

  struct drm_plane;

  
  void drm_modeset_lock_all(struct drm_device *dev);
  void drm_modeset_unlock_all(struct drm_device *dev);
  void drm_warn_on_modeset_not_all_locked(struct drm_device *dev);

  int drm_modeset_lock_all_ctx(struct drm_device *dev,
  			     struct drm_modeset_acquire_ctx *ctx);

  /**
   * DRM_MODESET_LOCK_ALL_BEGIN - Helper to acquire modeset locks
   * @dev: drm device
   * @ctx: local modeset acquire context, will be dereferenced
   * @flags: DRM_MODESET_ACQUIRE_* flags to pass to drm_modeset_acquire_init()
   * @ret: local ret/err/etc variable to track error status
   *
   * Use these macros to simplify grabbing all modeset locks using a local
   * context. This has the advantage of reducing boilerplate, but also properly
   * checking return values where appropriate.
   *
   * Any code run between BEGIN and END will be holding the modeset locks.
   *
   * This must be paired with DRM_MODESET_LOCK_ALL_END(). We will jump back and
   * forth between the labels on deadlock and error conditions.
   *
   * Drivers can acquire additional modeset locks. If any lock acquisition
   * fails, the control flow needs to jump to DRM_MODESET_LOCK_ALL_END() with
   * the @ret parameter containing the return value of drm_modeset_lock().
   *
   * Returns:
   * The only possible value of ret immediately after DRM_MODESET_LOCK_ALL_BEGIN()
   * is 0, so no error checking is necessary
   */
  #define DRM_MODESET_LOCK_ALL_BEGIN(dev, ctx, flags, ret)		\
  	drm_modeset_acquire_init(&ctx, flags);				\
  modeset_lock_retry:							\
  	ret = drm_modeset_lock_all_ctx(dev, &ctx);			\
  	if (ret)							\
  		goto modeset_lock_fail;
  
  /**
   * DRM_MODESET_LOCK_ALL_END - Helper to release and cleanup modeset locks
   * @ctx: local modeset acquire context, will be dereferenced
   * @ret: local ret/err/etc variable to track error status
   *
   * The other side of DRM_MODESET_LOCK_ALL_BEGIN(). It will bounce back to BEGIN
   * if ret is -EDEADLK.
   *
   * It's important that you use the same ret variable for begin and end so
   * deadlock conditions are properly handled.
   *
   * Returns:
   * ret will be untouched unless it is -EDEADLK on entry. That means that if you
   * successfully acquire the locks, ret will be whatever your code sets it to. If
   * there is a deadlock or other failure with acquire or backoff, ret will be set
   * to that failure. In both of these cases the code between BEGIN/END will not
   * be run, so the failure will reflect the inability to grab the locks.
   */
  #define DRM_MODESET_LOCK_ALL_END(ctx, ret)				\
  modeset_lock_fail:							\
  	if (ret == -EDEADLK) {						\
  		ret = drm_modeset_backoff(&ctx);			\
  		if (!ret)						\
  			goto modeset_lock_retry;			\
  	}								\
  	drm_modeset_drop_locks(&ctx);					\
  	drm_modeset_acquire_fini(&ctx);

  #endif /* DRM_MODESET_LOCK_H_ */