drivers/char/drm/drm_context.c - kernel/msm-5.4 - Gitiles

 /**
  * \file drm_context.c
  * IOCTLs for generic contexts
  *
  * \author Rickard E. (Rik) Faith <faith@valinux.com>
  * \author Gareth Hughes <gareth@valinux.com>
  */

 /*
  * Created: Fri Nov 24 18:31:37 2000 by gareth@valinux.com
  *
  * Copyright 1999, 2000 Precision Insight, Inc., Cedar Park, Texas.
  * Copyright 2000 VA Linux Systems, Inc., Sunnyvale, California.
  * All Rights Reserved.
  *
  * 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 (including the next
  * paragraph) 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
  * VA LINUX SYSTEMS AND/OR ITS SUPPLIERS 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.
  */

 /*
  * ChangeLog:
  *  2001-11-16	Torsten Duwe <duwe@caldera.de>
  *		added context constructor/destructor hooks,
  *		needed by SiS driver's memory management.
  */

 #include "drmP.h"

 /******************************************************************/
 /** \name Context bitmap support */
 /*@{*/

 /**
  * Free a handle from the context bitmap.
  *
  * \param dev DRM device.
  * \param ctx_handle context handle.
  *
  * Clears the bit specified by \p ctx_handle in drm_device::ctx_bitmap and the entry
  * in drm_device::ctx_idr, while holding the drm_device::struct_mutex
  * lock.
  */
 void drm_ctxbitmap_free(struct drm_device * dev, int ctx_handle)
 {
 	mutex_lock(&dev->struct_mutex);
 	idr_remove(&dev->ctx_idr, ctx_handle);
 	mutex_unlock(&dev->struct_mutex);
 }

 /**
  * Context bitmap allocation.
  *
  * \param dev DRM device.
  * \return (non-negative) context handle on success or a negative number on failure.
  *
  * Allocate a new idr from drm_device::ctx_idr while holding the
  * drm_device::struct_mutex lock.
  */
 static int drm_ctxbitmap_next(struct drm_device * dev)
 {
 	int new_id;
 	int ret;

 again:
 	if (idr_pre_get(&dev->ctx_idr, GFP_KERNEL) == 0) {
 		DRM_ERROR("Out of memory expanding drawable idr\n");
 		return -ENOMEM;
 	}
 	mutex_lock(&dev->struct_mutex);
 	ret = idr_get_new_above(&dev->ctx_idr, NULL,
 				DRM_RESERVED_CONTEXTS, &new_id);
 	if (ret == -EAGAIN) {
 		mutex_unlock(&dev->struct_mutex);
 		goto again;
 	}
 	mutex_unlock(&dev->struct_mutex);
 	return new_id;
 }

 /**
  * Context bitmap initialization.
  *
  * \param dev DRM device.
  *
  * Initialise the drm_device::ctx_idr
  */
 int drm_ctxbitmap_init(struct drm_device * dev)
 {
 	idr_init(&dev->ctx_idr);
 	return 0;
 }

 /**
  * Context bitmap cleanup.
  *
  * \param dev DRM device.
  *
  * Free all idr members using drm_ctx_sarea_free helper function
  * while holding the drm_device::struct_mutex lock.
  */
 void drm_ctxbitmap_cleanup(struct drm_device * dev)
 {
 	mutex_lock(&dev->struct_mutex);
 	idr_remove_all(&dev->ctx_idr);
 	mutex_unlock(&dev->struct_mutex);
 }

 /*@}*/

 /******************************************************************/
 /** \name Per Context SAREA Support */
 /*@{*/

 /**
  * Get per-context SAREA.
  *
  * \param inode device inode.
  * \param file_priv DRM file private.
  * \param cmd command.
  * \param arg user argument pointing to a drm_ctx_priv_map structure.
  * \return zero on success or a negative number on failure.
  *
  * Gets the map from drm_device::ctx_idr with the handle specified and
  * returns its handle.
  */
 int drm_getsareactx(struct inode *inode, struct drm_file *file_priv,
 		    unsigned int cmd, unsigned long arg)
 {
 	struct drm_device *dev = file_priv->head->dev;
 	struct drm_ctx_priv_map __user *argp = (void __user *)arg;
 	struct drm_ctx_priv_map request;
 	struct drm_map *map;
 	struct drm_map_list *_entry;

 	if (copy_from_user(&request, argp, sizeof(request)))
 		return -EFAULT;

 	mutex_lock(&dev->struct_mutex);

 	map = idr_find(&dev->ctx_idr, request.ctx_id);
 	if (!map) {
 		mutex_unlock(&dev->struct_mutex);
 		return -EINVAL;
 	}

 	mutex_unlock(&dev->struct_mutex);

 	request.handle = NULL;
 	list_for_each_entry(_entry, &dev->maplist, head) {
 		if (_entry->map == map) {
 			request.handle =
 			    (void *)(unsigned long)_entry->user_token;
 			break;
 		}
 	}
 	if (request.handle == NULL)
 		return -EINVAL;

 	if (copy_to_user(argp, &request, sizeof(request)))
 		return -EFAULT;
 	return 0;
 }

 /**
  * Set per-context SAREA.
  *
  * \param inode device inode.
  * \param file_priv DRM file private.
  * \param cmd command.
  * \param arg user argument pointing to a drm_ctx_priv_map structure.
  * \return zero on success or a negative number on failure.
  *
  * Searches the mapping specified in \p arg and update the entry in
  * drm_device::ctx_idr with it.
  */
 int drm_setsareactx(struct inode *inode, struct drm_file *file_priv,
 		    unsigned int cmd, unsigned long arg)
 {
 	struct drm_device *dev = file_priv->head->dev;
 	struct drm_ctx_priv_map request;
 	struct drm_map *map = NULL;
 	struct drm_map_list *r_list = NULL;

 	if (copy_from_user(&request,
 			   (struct drm_ctx_priv_map __user *) arg,
 			   sizeof(request)))
 		return -EFAULT;

 	mutex_lock(&dev->struct_mutex);
 	list_for_each_entry(r_list, &dev->maplist, head) {
 		if (r_list->map
 		    && r_list->user_token == (unsigned long)request.handle)
 			goto found;
 	}
       bad:
 	mutex_unlock(&dev->struct_mutex);
 	return -EINVAL;

       found:
 	map = r_list->map;
 	if (!map)
 		goto bad;

 	if (IS_ERR(idr_replace(&dev->ctx_idr, map, request.ctx_id)))
 		goto bad;

 	mutex_unlock(&dev->struct_mutex);
 	return 0;
 }

 /*@}*/

 /******************************************************************/
 /** \name The actual DRM context handling routines */
 /*@{*/

 /**
  * Switch context.
  *
  * \param dev DRM device.
  * \param old old context handle.
  * \param new new context handle.
  * \return zero on success or a negative number on failure.
  *
  * Attempt to set drm_device::context_flag.
  */
 static int drm_context_switch(struct drm_device * dev, int old, int new)
 {
 	if (test_and_set_bit(0, &dev->context_flag)) {
 		DRM_ERROR("Reentering -- FIXME\n");
 		return -EBUSY;
 	}

 	DRM_DEBUG("Context switch from %d to %d\n", old, new);

 	if (new == dev->last_context) {
 		clear_bit(0, &dev->context_flag);
 		return 0;
 	}

 	return 0;
 }

 /**
  * Complete context switch.
  *
  * \param dev DRM device.
  * \param new new context handle.
  * \return zero on success or a negative number on failure.
  *
  * Updates drm_device::last_context and drm_device::last_switch. Verifies the
  * hardware lock is held, clears the drm_device::context_flag and wakes up
  * drm_device::context_wait.
  */
 static int drm_context_switch_complete(struct drm_device * dev, int new)
 {
 	dev->last_context = new;	/* PRE/POST: This is the _only_ writer. */
 	dev->last_switch = jiffies;

 	if (!_DRM_LOCK_IS_HELD(dev->lock.hw_lock->lock)) {
 		DRM_ERROR("Lock isn't held after context switch\n");
 	}

 	/* If a context switch is ever initiated
 	   when the kernel holds the lock, release
 	   that lock here. */
 	clear_bit(0, &dev->context_flag);
 	wake_up(&dev->context_wait);

 	return 0;
 }

 /**
  * Reserve contexts.
  *
  * \param inode device inode.
  * \param file_priv DRM file private.
  * \param cmd command.
  * \param arg user argument pointing to a drm_ctx_res structure.
  * \return zero on success or a negative number on failure.
  */
 int drm_resctx(struct inode *inode, struct drm_file *file_priv,
 	       unsigned int cmd, unsigned long arg)
 {
 	struct drm_ctx_res res;
 	struct drm_ctx_res __user *argp = (void __user *)arg;
 	struct drm_ctx ctx;
 	int i;

 	if (copy_from_user(&res, argp, sizeof(res)))
 		return -EFAULT;

 	if (res.count >= DRM_RESERVED_CONTEXTS) {
 		memset(&ctx, 0, sizeof(ctx));
 		for (i = 0; i < DRM_RESERVED_CONTEXTS; i++) {
 			ctx.handle = i;
 			if (copy_to_user(&res.contexts[i], &ctx, sizeof(ctx)))
 				return -EFAULT;
 		}
 	}
 	res.count = DRM_RESERVED_CONTEXTS;

 	if (copy_to_user(argp, &res, sizeof(res)))
 		return -EFAULT;
 	return 0;
 }

 /**
  * Add context.
  *
  * \param inode device inode.
  * \param file_priv DRM file private.
  * \param cmd command.
  * \param arg user argument pointing to a drm_ctx structure.
  * \return zero on success or a negative number on failure.
  *
  * Get a new handle for the context and copy to userspace.
  */
 int drm_addctx(struct inode *inode, struct drm_file *file_priv,
 	       unsigned int cmd, unsigned long arg)
 {
 	struct drm_device *dev = file_priv->head->dev;
 	struct drm_ctx_list *ctx_entry;
 	struct drm_ctx __user *argp = (void __user *)arg;
 	struct drm_ctx ctx;

 	if (copy_from_user(&ctx, argp, sizeof(ctx)))
 		return -EFAULT;

 	ctx.handle = drm_ctxbitmap_next(dev);
 	if (ctx.handle == DRM_KERNEL_CONTEXT) {
 		/* Skip kernel's context and get a new one. */
 		ctx.handle = drm_ctxbitmap_next(dev);
 	}
 	DRM_DEBUG("%d\n", ctx.handle);
 	if (ctx.handle == -1) {
 		DRM_DEBUG("Not enough free contexts.\n");
 		/* Should this return -EBUSY instead? */
 		return -ENOMEM;
 	}

 	if (ctx.handle != DRM_KERNEL_CONTEXT) {
 		if (dev->driver->context_ctor)
 			if (!dev->driver->context_ctor(dev, ctx.handle)) {
 				DRM_DEBUG("Running out of ctxs or memory.\n");
 				return -ENOMEM;
 			}
 	}

 	ctx_entry = drm_alloc(sizeof(*ctx_entry), DRM_MEM_CTXLIST);
 	if (!ctx_entry) {
 		DRM_DEBUG("out of memory\n");
 		return -ENOMEM;
 	}

 	INIT_LIST_HEAD(&ctx_entry->head);
 	ctx_entry->handle = ctx.handle;
 	ctx_entry->tag = file_priv;

 	mutex_lock(&dev->ctxlist_mutex);
 	list_add(&ctx_entry->head, &dev->ctxlist);
 	++dev->ctx_count;
 	mutex_unlock(&dev->ctxlist_mutex);

 	if (copy_to_user(argp, &ctx, sizeof(ctx)))
 		return -EFAULT;
 	return 0;
 }

 int drm_modctx(struct inode *inode, struct drm_file *file_priv,
 	       unsigned int cmd, unsigned long arg)
 {
 	/* This does nothing */
 	return 0;
 }

 /**
  * Get context.
  *
  * \param inode device inode.
  * \param file_priv DRM file private.
  * \param cmd command.
  * \param arg user argument pointing to a drm_ctx structure.
  * \return zero on success or a negative number on failure.
  */
 int drm_getctx(struct inode *inode, struct drm_file *file_priv,
 	       unsigned int cmd, unsigned long arg)
 {
 	struct drm_ctx __user *argp = (void __user *)arg;
 	struct drm_ctx ctx;

 	if (copy_from_user(&ctx, argp, sizeof(ctx)))
 		return -EFAULT;

 	/* This is 0, because we don't handle any context flags */
 	ctx.flags = 0;

 	if (copy_to_user(argp, &ctx, sizeof(ctx)))
 		return -EFAULT;
 	return 0;
 }

 /**
  * Switch context.
  *
  * \param inode device inode.
  * \param file_priv DRM file private.
  * \param cmd command.
  * \param arg user argument pointing to a drm_ctx structure.
  * \return zero on success or a negative number on failure.
  *
  * Calls context_switch().
  */
 int drm_switchctx(struct inode *inode, struct drm_file *file_priv,
 		  unsigned int cmd, unsigned long arg)
 {
 	struct drm_device *dev = file_priv->head->dev;
 	struct drm_ctx ctx;

 	if (copy_from_user(&ctx, (struct drm_ctx __user *) arg, sizeof(ctx)))
 		return -EFAULT;

 	DRM_DEBUG("%d\n", ctx.handle);
 	return drm_context_switch(dev, dev->last_context, ctx.handle);
 }

 /**
  * New context.
  *
  * \param inode device inode.
  * \param file_priv DRM file private.
  * \param cmd command.
  * \param arg user argument pointing to a drm_ctx structure.
  * \return zero on success or a negative number on failure.
  *
  * Calls context_switch_complete().
  */
 int drm_newctx(struct inode *inode, struct drm_file *file_priv,
 	       unsigned int cmd, unsigned long arg)
 {
 	struct drm_device *dev = file_priv->head->dev;
 	struct drm_ctx ctx;

 	if (copy_from_user(&ctx, (struct drm_ctx __user *) arg, sizeof(ctx)))
 		return -EFAULT;

 	DRM_DEBUG("%d\n", ctx.handle);
 	drm_context_switch_complete(dev, ctx.handle);

 	return 0;
 }

 /**
  * Remove context.
  *
  * \param inode device inode.
  * \param file_priv DRM file private.
  * \param cmd command.
  * \param arg user argument pointing to a drm_ctx structure.
  * \return zero on success or a negative number on failure.
  *
  * If not the special kernel context, calls ctxbitmap_free() to free the specified context.
  */
 int drm_rmctx(struct inode *inode, struct drm_file *file_priv,
 	      unsigned int cmd, unsigned long arg)
 {
 	struct drm_device *dev = file_priv->head->dev;
 	struct drm_ctx ctx;

 	if (copy_from_user(&ctx, (struct drm_ctx __user *) arg, sizeof(ctx)))
 		return -EFAULT;

 	DRM_DEBUG("%d\n", ctx.handle);
 	if (ctx.handle == DRM_KERNEL_CONTEXT + 1) {
 		file_priv->remove_auth_on_close = 1;
 	}
 	if (ctx.handle != DRM_KERNEL_CONTEXT) {
 		if (dev->driver->context_dtor)
 			dev->driver->context_dtor(dev, ctx.handle);
 		drm_ctxbitmap_free(dev, ctx.handle);
 	}

 	mutex_lock(&dev->ctxlist_mutex);
 	if (!list_empty(&dev->ctxlist)) {
 		struct drm_ctx_list *pos, *n;

 		list_for_each_entry_safe(pos, n, &dev->ctxlist, head) {
 			if (pos->handle == ctx.handle) {
 				list_del(&pos->head);
 				drm_free(pos, sizeof(*pos), DRM_MEM_CTXLIST);
 				--dev->ctx_count;
 			}
 		}
 	}
 	mutex_unlock(&dev->ctxlist_mutex);

 	return 0;
 }

 /*@}*/
	/**
	* \file drm_context.c
	* IOCTLs for generic contexts
	*
	* \author Rickard E. (Rik) Faith <faith@valinux.com>
	* \author Gareth Hughes <gareth@valinux.com>
	*/

	/*
	* Created: Fri Nov 24 18:31:37 2000 by gareth@valinux.com
	*
	* Copyright 1999, 2000 Precision Insight, Inc., Cedar Park, Texas.
	* Copyright 2000 VA Linux Systems, Inc., Sunnyvale, California.
	* All Rights Reserved.
	*
	* 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 (including the next
	* paragraph) 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
	* VA LINUX SYSTEMS AND/OR ITS SUPPLIERS 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.
	*/

	/*
	* ChangeLog:
	* 2001-11-16 Torsten Duwe <duwe@caldera.de>
	* added context constructor/destructor hooks,
	* needed by SiS driver's memory management.
	*/

	#include "drmP.h"

	/******************************************************************/
	/** \name Context bitmap support */
	/@{/

	/**
	* Free a handle from the context bitmap.
	*
	* \param dev DRM device.
	* \param ctx_handle context handle.
	*
	* Clears the bit specified by \p ctx_handle in drm_device::ctx_bitmap and the entry
	* in drm_device::ctx_idr, while holding the drm_device::struct_mutex
	* lock.
	*/
	void drm_ctxbitmap_free(struct drm_device * dev, int ctx_handle)
	{
	mutex_lock(&dev->struct_mutex);
	idr_remove(&dev->ctx_idr, ctx_handle);
	mutex_unlock(&dev->struct_mutex);
	}

	/**
	* Context bitmap allocation.
	*
	* \param dev DRM device.
	* \return (non-negative) context handle on success or a negative number on failure.
	*
	* Allocate a new idr from drm_device::ctx_idr while holding the
	* drm_device::struct_mutex lock.
	*/
	static int drm_ctxbitmap_next(struct drm_device * dev)
	{
	int new_id;
	int ret;

	again:
	if (idr_pre_get(&dev->ctx_idr, GFP_KERNEL) == 0) {
	DRM_ERROR("Out of memory expanding drawable idr\n");
	return -ENOMEM;
	}
	mutex_lock(&dev->struct_mutex);
	ret = idr_get_new_above(&dev->ctx_idr, NULL,
	DRM_RESERVED_CONTEXTS, &new_id);
	if (ret == -EAGAIN) {
	mutex_unlock(&dev->struct_mutex);
	goto again;
	}
	mutex_unlock(&dev->struct_mutex);
	return new_id;
	}

	/**
	* Context bitmap initialization.
	*
	* \param dev DRM device.
	*
	* Initialise the drm_device::ctx_idr
	*/
	int drm_ctxbitmap_init(struct drm_device * dev)
	{
	idr_init(&dev->ctx_idr);
	return 0;
	}

	/**
	* Context bitmap cleanup.
	*
	* \param dev DRM device.
	*
	* Free all idr members using drm_ctx_sarea_free helper function
	* while holding the drm_device::struct_mutex lock.
	*/
	void drm_ctxbitmap_cleanup(struct drm_device * dev)
	{
	mutex_lock(&dev->struct_mutex);
	idr_remove_all(&dev->ctx_idr);
	mutex_unlock(&dev->struct_mutex);
	}

	/@}/

	/******************************************************************/
	/** \name Per Context SAREA Support */
	/@{/

	/**
	* Get per-context SAREA.
	*
	* \param inode device inode.
	* \param file_priv DRM file private.
	* \param cmd command.
	* \param arg user argument pointing to a drm_ctx_priv_map structure.
	* \return zero on success or a negative number on failure.
	*
	* Gets the map from drm_device::ctx_idr with the handle specified and
	* returns its handle.
	*/
	int drm_getsareactx(struct inode inode, struct drm_file file_priv,
	unsigned int cmd, unsigned long arg)
	{
	struct drm_device *dev = file_priv->head->dev;
	struct drm_ctx_priv_map __user argp = (void __user )arg;
	struct drm_ctx_priv_map request;
	struct drm_map *map;
	struct drm_map_list *_entry;

	if (copy_from_user(&request, argp, sizeof(request)))
	return -EFAULT;

	mutex_lock(&dev->struct_mutex);

	map = idr_find(&dev->ctx_idr, request.ctx_id);
	if (!map) {
	mutex_unlock(&dev->struct_mutex);
	return -EINVAL;
	}

	mutex_unlock(&dev->struct_mutex);

	request.handle = NULL;
	list_for_each_entry(_entry, &dev->maplist, head) {
	if (_entry->map == map) {
	request.handle =
	(void *)(unsigned long)_entry->user_token;
	break;
	}
	}
	if (request.handle == NULL)
	return -EINVAL;

	if (copy_to_user(argp, &request, sizeof(request)))
	return -EFAULT;
	return 0;
	}

	/**
	* Set per-context SAREA.
	*
	* \param inode device inode.
	* \param file_priv DRM file private.
	* \param cmd command.
	* \param arg user argument pointing to a drm_ctx_priv_map structure.
	* \return zero on success or a negative number on failure.
	*
	* Searches the mapping specified in \p arg and update the entry in
	* drm_device::ctx_idr with it.
	*/
	int drm_setsareactx(struct inode inode, struct drm_file file_priv,
	unsigned int cmd, unsigned long arg)
	{
	struct drm_device *dev = file_priv->head->dev;
	struct drm_ctx_priv_map request;
	struct drm_map *map = NULL;
	struct drm_map_list *r_list = NULL;

	if (copy_from_user(&request,
	(struct drm_ctx_priv_map __user *) arg,
	sizeof(request)))
	return -EFAULT;

	mutex_lock(&dev->struct_mutex);
	list_for_each_entry(r_list, &dev->maplist, head) {
	if (r_list->map
	&& r_list->user_token == (unsigned long)request.handle)
	goto found;
	}
	bad:
	mutex_unlock(&dev->struct_mutex);
	return -EINVAL;

	found:
	map = r_list->map;
	if (!map)
	goto bad;

	if (IS_ERR(idr_replace(&dev->ctx_idr, map, request.ctx_id)))
	goto bad;

	mutex_unlock(&dev->struct_mutex);
	return 0;
	}

	/@}/

	/******************************************************************/
	/** \name The actual DRM context handling routines */
	/@{/

	/**
	* Switch context.
	*
	* \param dev DRM device.
	* \param old old context handle.
	* \param new new context handle.
	* \return zero on success or a negative number on failure.
	*
	* Attempt to set drm_device::context_flag.
	*/
	static int drm_context_switch(struct drm_device * dev, int old, int new)
	{
	if (test_and_set_bit(0, &dev->context_flag)) {
	DRM_ERROR("Reentering -- FIXME\n");
	return -EBUSY;
	}

	DRM_DEBUG("Context switch from %d to %d\n", old, new);

	if (new == dev->last_context) {
	clear_bit(0, &dev->context_flag);
	return 0;
	}

	return 0;
	}

	/**
	* Complete context switch.
	*
	* \param dev DRM device.
	* \param new new context handle.
	* \return zero on success or a negative number on failure.
	*
	* Updates drm_device::last_context and drm_device::last_switch. Verifies the
	* hardware lock is held, clears the drm_device::context_flag and wakes up
	* drm_device::context_wait.
	*/
	static int drm_context_switch_complete(struct drm_device * dev, int new)
	{
	dev->last_context = new; /* PRE/POST: This is the _only_ writer. */
	dev->last_switch = jiffies;

	if (!_DRM_LOCK_IS_HELD(dev->lock.hw_lock->lock)) {
	DRM_ERROR("Lock isn't held after context switch\n");
	}

	/* If a context switch is ever initiated
	when the kernel holds the lock, release
	that lock here. */
	clear_bit(0, &dev->context_flag);
	wake_up(&dev->context_wait);

	return 0;
	}

	/**
	* Reserve contexts.
	*
	* \param inode device inode.
	* \param file_priv DRM file private.
	* \param cmd command.
	* \param arg user argument pointing to a drm_ctx_res structure.
	* \return zero on success or a negative number on failure.
	*/
	int drm_resctx(struct inode inode, struct drm_file file_priv,
	unsigned int cmd, unsigned long arg)
	{
	struct drm_ctx_res res;
	struct drm_ctx_res __user argp = (void __user )arg;
	struct drm_ctx ctx;
	int i;

	if (copy_from_user(&res, argp, sizeof(res)))
	return -EFAULT;

	if (res.count >= DRM_RESERVED_CONTEXTS) {
	memset(&ctx, 0, sizeof(ctx));
	for (i = 0; i < DRM_RESERVED_CONTEXTS; i++) {
	ctx.handle = i;
	if (copy_to_user(&res.contexts[i], &ctx, sizeof(ctx)))
	return -EFAULT;
	}
	}
	res.count = DRM_RESERVED_CONTEXTS;

	if (copy_to_user(argp, &res, sizeof(res)))
	return -EFAULT;
	return 0;
	}

	/**
	* Add context.
	*
	* \param inode device inode.
	* \param file_priv DRM file private.
	* \param cmd command.
	* \param arg user argument pointing to a drm_ctx structure.
	* \return zero on success or a negative number on failure.
	*
	* Get a new handle for the context and copy to userspace.
	*/
	int drm_addctx(struct inode inode, struct drm_file file_priv,
	unsigned int cmd, unsigned long arg)
	{
	struct drm_device *dev = file_priv->head->dev;
	struct drm_ctx_list *ctx_entry;
	struct drm_ctx __user argp = (void __user )arg;
	struct drm_ctx ctx;

	if (copy_from_user(&ctx, argp, sizeof(ctx)))
	return -EFAULT;

	ctx.handle = drm_ctxbitmap_next(dev);
	if (ctx.handle == DRM_KERNEL_CONTEXT) {
	/* Skip kernel's context and get a new one. */
	ctx.handle = drm_ctxbitmap_next(dev);
	}
	DRM_DEBUG("%d\n", ctx.handle);
	if (ctx.handle == -1) {
	DRM_DEBUG("Not enough free contexts.\n");
	/* Should this return -EBUSY instead? */
	return -ENOMEM;
	}

	if (ctx.handle != DRM_KERNEL_CONTEXT) {
	if (dev->driver->context_ctor)
	if (!dev->driver->context_ctor(dev, ctx.handle)) {
	DRM_DEBUG("Running out of ctxs or memory.\n");
	return -ENOMEM;
	}
	}

	ctx_entry = drm_alloc(sizeof(*ctx_entry), DRM_MEM_CTXLIST);
	if (!ctx_entry) {
	DRM_DEBUG("out of memory\n");
	return -ENOMEM;
	}

	INIT_LIST_HEAD(&ctx_entry->head);
	ctx_entry->handle = ctx.handle;
	ctx_entry->tag = file_priv;

	mutex_lock(&dev->ctxlist_mutex);
	list_add(&ctx_entry->head, &dev->ctxlist);
	++dev->ctx_count;
	mutex_unlock(&dev->ctxlist_mutex);

	if (copy_to_user(argp, &ctx, sizeof(ctx)))
	return -EFAULT;
	return 0;
	}

	int drm_modctx(struct inode inode, struct drm_file file_priv,
	unsigned int cmd, unsigned long arg)
	{
	/* This does nothing */
	return 0;
	}

	/**
	* Get context.
	*
	* \param inode device inode.
	* \param file_priv DRM file private.
	* \param cmd command.
	* \param arg user argument pointing to a drm_ctx structure.
	* \return zero on success or a negative number on failure.
	*/
	int drm_getctx(struct inode inode, struct drm_file file_priv,
	unsigned int cmd, unsigned long arg)
	{
	struct drm_ctx __user argp = (void __user )arg;
	struct drm_ctx ctx;

	if (copy_from_user(&ctx, argp, sizeof(ctx)))
	return -EFAULT;

	/* This is 0, because we don't handle any context flags */
	ctx.flags = 0;

	if (copy_to_user(argp, &ctx, sizeof(ctx)))
	return -EFAULT;
	return 0;
	}

	/**
	* Switch context.
	*
	* \param inode device inode.
	* \param file_priv DRM file private.
	* \param cmd command.
	* \param arg user argument pointing to a drm_ctx structure.
	* \return zero on success or a negative number on failure.
	*
	* Calls context_switch().
	*/
	int drm_switchctx(struct inode inode, struct drm_file file_priv,
	unsigned int cmd, unsigned long arg)
	{
	struct drm_device *dev = file_priv->head->dev;
	struct drm_ctx ctx;

	if (copy_from_user(&ctx, (struct drm_ctx __user *) arg, sizeof(ctx)))
	return -EFAULT;

	DRM_DEBUG("%d\n", ctx.handle);
	return drm_context_switch(dev, dev->last_context, ctx.handle);
	}

	/**
	* New context.
	*
	* \param inode device inode.
	* \param file_priv DRM file private.
	* \param cmd command.
	* \param arg user argument pointing to a drm_ctx structure.
	* \return zero on success or a negative number on failure.
	*
	* Calls context_switch_complete().
	*/
	int drm_newctx(struct inode inode, struct drm_file file_priv,
	unsigned int cmd, unsigned long arg)
	{
	struct drm_device *dev = file_priv->head->dev;
	struct drm_ctx ctx;

	if (copy_from_user(&ctx, (struct drm_ctx __user *) arg, sizeof(ctx)))
	return -EFAULT;

	DRM_DEBUG("%d\n", ctx.handle);
	drm_context_switch_complete(dev, ctx.handle);

	return 0;
	}

	/**
	* Remove context.
	*
	* \param inode device inode.
	* \param file_priv DRM file private.
	* \param cmd command.
	* \param arg user argument pointing to a drm_ctx structure.
	* \return zero on success or a negative number on failure.
	*
	* If not the special kernel context, calls ctxbitmap_free() to free the specified context.
	*/
	int drm_rmctx(struct inode inode, struct drm_file file_priv,
	unsigned int cmd, unsigned long arg)
	{
	struct drm_device *dev = file_priv->head->dev;
	struct drm_ctx ctx;

	if (copy_from_user(&ctx, (struct drm_ctx __user *) arg, sizeof(ctx)))
	return -EFAULT;

	DRM_DEBUG("%d\n", ctx.handle);
	if (ctx.handle == DRM_KERNEL_CONTEXT + 1) {
	file_priv->remove_auth_on_close = 1;
	}
	if (ctx.handle != DRM_KERNEL_CONTEXT) {
	if (dev->driver->context_dtor)
	dev->driver->context_dtor(dev, ctx.handle);
	drm_ctxbitmap_free(dev, ctx.handle);
	}

	mutex_lock(&dev->ctxlist_mutex);
	if (!list_empty(&dev->ctxlist)) {
	struct drm_ctx_list pos, n;

	list_for_each_entry_safe(pos, n, &dev->ctxlist, head) {
	if (pos->handle == ctx.handle) {
	list_del(&pos->head);
	drm_free(pos, sizeof(*pos), DRM_MEM_CTXLIST);
	--dev->ctx_count;
	}
	}
	}
	mutex_unlock(&dev->ctxlist_mutex);

	return 0;
	}

	/@}/