drivers/gpu/vga/vga_switcheroo.c - kernel/msm - Gitiles

 /*
  * Copyright (c) 2010 Red Hat Inc.
  * Author : Dave Airlie <airlied@redhat.com>
  *
  *
  * Licensed under GPLv2
  *
  * vga_switcheroo.c - Support for laptop with dual GPU using one set of outputs

  Switcher interface - methods require for ATPX and DCM
  - switchto - this throws the output MUX switch
  - discrete_set_power - sets the power state for the discrete card

  GPU driver interface
  - set_gpu_state - this should do the equiv of s/r for the card
 		  - this should *not* set the discrete power state
  - switch_check  - check if the device is in a position to switch now
  */

 #include <linux/module.h>
 #include <linux/dmi.h>
 #include <linux/seq_file.h>
 #include <linux/uaccess.h>
 #include <linux/fs.h>
 #include <linux/debugfs.h>
 #include <linux/fb.h>

 #include <linux/pci.h>
 #include <linux/vga_switcheroo.h>

 struct vga_switcheroo_client {
 	struct pci_dev *pdev;
 	struct fb_info *fb_info;
 	int pwr_state;
 	void (*set_gpu_state)(struct pci_dev *pdev, enum vga_switcheroo_state);
 	bool (*can_switch)(struct pci_dev *pdev);
 	int id;
 	bool active;
 };

 static DEFINE_MUTEX(vgasr_mutex);

 struct vgasr_priv {

 	bool active;
 	bool delayed_switch_active;
 	enum vga_switcheroo_client_id delayed_client_id;

 	struct dentry *debugfs_root;
 	struct dentry *switch_file;

 	int registered_clients;
 	struct vga_switcheroo_client clients[VGA_SWITCHEROO_MAX_CLIENTS];

 	struct vga_switcheroo_handler *handler;
 };

 static int vga_switcheroo_debugfs_init(struct vgasr_priv *priv);
 static void vga_switcheroo_debugfs_fini(struct vgasr_priv *priv);

 /* only one switcheroo per system */
 static struct vgasr_priv vgasr_priv;

 int vga_switcheroo_register_handler(struct vga_switcheroo_handler *handler)
 {
 	mutex_lock(&vgasr_mutex);
 	if (vgasr_priv.handler) {
 		mutex_unlock(&vgasr_mutex);
 		return -EINVAL;
 	}

 	vgasr_priv.handler = handler;
 	mutex_unlock(&vgasr_mutex);
 	return 0;
 }
 EXPORT_SYMBOL(vga_switcheroo_register_handler);

 void vga_switcheroo_unregister_handler(void)
 {
 	mutex_lock(&vgasr_mutex);
 	vgasr_priv.handler = NULL;
 	mutex_unlock(&vgasr_mutex);
 }
 EXPORT_SYMBOL(vga_switcheroo_unregister_handler);

 static void vga_switcheroo_enable(void)
 {
 	int i;
 	int ret;
 	/* call the handler to init */
 	vgasr_priv.handler->init();

 	for (i = 0; i < VGA_SWITCHEROO_MAX_CLIENTS; i++) {
 		ret = vgasr_priv.handler->get_client_id(vgasr_priv.clients[i].pdev);
 		if (ret < 0)
 			return;

 		vgasr_priv.clients[i].id = ret;
 	}
 	vga_switcheroo_debugfs_init(&vgasr_priv);
 	vgasr_priv.active = true;
 }

 int vga_switcheroo_register_client(struct pci_dev *pdev,
 				   void (*set_gpu_state)(struct pci_dev *pdev, enum vga_switcheroo_state),
 				   bool (*can_switch)(struct pci_dev *pdev))
 {
 	int index;

 	mutex_lock(&vgasr_mutex);
 	/* don't do IGD vs DIS here */
 	if (vgasr_priv.registered_clients & 1)
 		index = 1;
 	else
 		index = 0;

 	vgasr_priv.clients[index].pwr_state = VGA_SWITCHEROO_ON;
 	vgasr_priv.clients[index].pdev = pdev;
 	vgasr_priv.clients[index].set_gpu_state = set_gpu_state;
 	vgasr_priv.clients[index].can_switch = can_switch;
 	vgasr_priv.clients[index].id = -1;
 	if (pdev->resource[PCI_ROM_RESOURCE].flags & IORESOURCE_ROM_SHADOW)
 		vgasr_priv.clients[index].active = true;

 	vgasr_priv.registered_clients |= (1 << index);

 	/* if we get two clients + handler */
 	if (vgasr_priv.registered_clients == 0x3 && vgasr_priv.handler) {
 		printk(KERN_INFO "vga_switcheroo: enabled\n");
 		vga_switcheroo_enable();
 	}
 	mutex_unlock(&vgasr_mutex);
 	return 0;
 }
 EXPORT_SYMBOL(vga_switcheroo_register_client);

 void vga_switcheroo_unregister_client(struct pci_dev *pdev)
 {
 	int i;

 	mutex_lock(&vgasr_mutex);
 	for (i = 0; i < VGA_SWITCHEROO_MAX_CLIENTS; i++) {
 		if (vgasr_priv.clients[i].pdev == pdev) {
 			vgasr_priv.registered_clients &= ~(1 << i);
 			break;
 		}
 	}

 	printk(KERN_INFO "vga_switcheroo: disabled\n");
 	vga_switcheroo_debugfs_fini(&vgasr_priv);
 	vgasr_priv.active = false;
 	mutex_unlock(&vgasr_mutex);
 }
 EXPORT_SYMBOL(vga_switcheroo_unregister_client);

 void vga_switcheroo_client_fb_set(struct pci_dev *pdev,
 				 struct fb_info *info)
 {
 	int i;

 	mutex_lock(&vgasr_mutex);
 	for (i = 0; i < VGA_SWITCHEROO_MAX_CLIENTS; i++) {
 		if (vgasr_priv.clients[i].pdev == pdev) {
 			vgasr_priv.clients[i].fb_info = info;
 			break;
 		}
 	}
 	mutex_unlock(&vgasr_mutex);
 }
 EXPORT_SYMBOL(vga_switcheroo_client_fb_set);

 static int vga_switcheroo_show(struct seq_file *m, void *v)
 {
 	int i;
 	mutex_lock(&vgasr_mutex);
 	for (i = 0; i < VGA_SWITCHEROO_MAX_CLIENTS; i++) {
 		seq_printf(m, "%d:%s:%c:%s:%s\n", i,
 			   vgasr_priv.clients[i].id == VGA_SWITCHEROO_DIS ? "DIS" : "IGD",
 			   vgasr_priv.clients[i].active ? '+' : ' ',
 			   vgasr_priv.clients[i].pwr_state ? "Pwr" : "Off",
 			   pci_name(vgasr_priv.clients[i].pdev));
 	}
 	mutex_unlock(&vgasr_mutex);
 	return 0;
 }

 static int vga_switcheroo_debugfs_open(struct inode *inode, struct file *file)
 {
 	return single_open(file, vga_switcheroo_show, NULL);
 }

 static int vga_switchon(struct vga_switcheroo_client *client)
 {
 	int ret;

 	ret = vgasr_priv.handler->power_state(client->id, VGA_SWITCHEROO_ON);
 	/* call the driver callback to turn on device */
 	client->set_gpu_state(client->pdev, VGA_SWITCHEROO_ON);
 	client->pwr_state = VGA_SWITCHEROO_ON;
 	return 0;
 }

 static int vga_switchoff(struct vga_switcheroo_client *client)
 {
 	/* call the driver callback to turn off device */
 	client->set_gpu_state(client->pdev, VGA_SWITCHEROO_OFF);
 	vgasr_priv.handler->power_state(client->id, VGA_SWITCHEROO_OFF);
 	client->pwr_state = VGA_SWITCHEROO_OFF;
 	return 0;
 }

 static int vga_switchto(struct vga_switcheroo_client *new_client)
 {
 	int ret;
 	int i;
 	struct vga_switcheroo_client *active = NULL;

 	if (new_client->active == true)
 		return 0;

 	for (i = 0; i < VGA_SWITCHEROO_MAX_CLIENTS; i++) {
 		if (vgasr_priv.clients[i].active == true) {
 			active = &vgasr_priv.clients[i];
 			break;
 		}
 	}
 	if (!active)
 		return 0;

 	/* power up the first device */
 	ret = pci_enable_device(new_client->pdev);
 	if (ret)
 		return ret;

 	if (new_client->pwr_state == VGA_SWITCHEROO_OFF)
 		vga_switchon(new_client);

 	/* swap shadow resource to denote boot VGA device has changed so X starts on new device */
 	active->active = false;

 	active->pdev->resource[PCI_ROM_RESOURCE].flags &= ~IORESOURCE_ROM_SHADOW;
 	new_client->pdev->resource[PCI_ROM_RESOURCE].flags |= IORESOURCE_ROM_SHADOW;

 	if (new_client->fb_info) {
 		struct fb_event event;
 		event.info = new_client->fb_info;
 		fb_notifier_call_chain(FB_EVENT_REMAP_ALL_CONSOLE, &event);
 	}

 	ret = vgasr_priv.handler->switchto(new_client->id);
 	if (ret)
 		return ret;

 	if (active->pwr_state == VGA_SWITCHEROO_ON)
 		vga_switchoff(active);

 	new_client->active = true;
 	return 0;
 }

 static ssize_t
 vga_switcheroo_debugfs_write(struct file *filp, const char __user *ubuf,
 			     size_t cnt, loff_t *ppos)
 {
 	char usercmd[64];
 	const char *pdev_name;
 	int i, ret;
 	bool delay = false, can_switch;
 	int client_id = -1;
 	struct vga_switcheroo_client *client = NULL;

 	if (cnt > 63)
 		cnt = 63;

 	if (copy_from_user(usercmd, ubuf, cnt))
 		return -EFAULT;

 	mutex_lock(&vgasr_mutex);

 	if (!vgasr_priv.active) {
 		cnt = -EINVAL;
 		goto out;
 	}

 	/* pwr off the device not in use */
 	if (strncmp(usercmd, "OFF", 3) == 0) {
 		for (i = 0; i < VGA_SWITCHEROO_MAX_CLIENTS; i++) {
 			if (vgasr_priv.clients[i].active)
 				continue;
 			if (vgasr_priv.clients[i].pwr_state == VGA_SWITCHEROO_ON)
 				vga_switchoff(&vgasr_priv.clients[i]);
 		}
 		goto out;
 	}
 	/* pwr on the device not in use */
 	if (strncmp(usercmd, "ON", 2) == 0) {
 		for (i = 0; i < VGA_SWITCHEROO_MAX_CLIENTS; i++) {
 			if (vgasr_priv.clients[i].active)
 				continue;
 			if (vgasr_priv.clients[i].pwr_state == VGA_SWITCHEROO_OFF)
 				vga_switchon(&vgasr_priv.clients[i]);
 		}
 		goto out;
 	}

 	/* request a delayed switch - test can we switch now */
 	if (strncmp(usercmd, "DIGD", 4) == 0) {
 		client_id = VGA_SWITCHEROO_IGD;
 		delay = true;
 	}

 	if (strncmp(usercmd, "DDIS", 4) == 0) {
 		client_id = VGA_SWITCHEROO_DIS;
 		delay = true;
 	}

 	if (strncmp(usercmd, "IGD", 3) == 0)
 		client_id = VGA_SWITCHEROO_IGD;

 	if (strncmp(usercmd, "DIS", 3) == 0)
 		client_id = VGA_SWITCHEROO_DIS;

 	if (client_id == -1)
 		goto out;

 	for (i = 0; i < VGA_SWITCHEROO_MAX_CLIENTS; i++) {
 		if (vgasr_priv.clients[i].id == client_id) {
 			client = &vgasr_priv.clients[i];
 			break;
 		}
 	}

 	vgasr_priv.delayed_switch_active = false;
 	/* okay we want a switch - test if devices are willing to switch */
 	can_switch = true;
 	for (i = 0; i < VGA_SWITCHEROO_MAX_CLIENTS; i++) {
 		can_switch = vgasr_priv.clients[i].can_switch(vgasr_priv.clients[i].pdev);
 		if (can_switch == false) {
 			printk(KERN_ERR "vga_switcheroo: client %d refused switch\n", i);
 			break;
 		}
 	}

 	if (can_switch == false && delay == false)
 		goto out;

 	if (can_switch == true) {
 		pdev_name = pci_name(client->pdev);
 		ret = vga_switchto(client);
 		if (ret)
 			printk(KERN_ERR "vga_switcheroo: switching failed %d\n", ret);
 	} else {
 		printk(KERN_INFO "vga_switcheroo: setting delayed switch to client %d\n", client->id);
 		vgasr_priv.delayed_switch_active = true;
 		vgasr_priv.delayed_client_id = client_id;

 		/* we should at least power up the card to
 		   make the switch faster */
 		if (client->pwr_state == VGA_SWITCHEROO_OFF)
 			vga_switchon(client);
 	}

 out:
 	mutex_unlock(&vgasr_mutex);
 	return cnt;
 }

 static const struct file_operations vga_switcheroo_debugfs_fops = {
 	.owner = THIS_MODULE,
 	.open = vga_switcheroo_debugfs_open,
 	.write = vga_switcheroo_debugfs_write,
 	.read = seq_read,
 	.llseek = seq_lseek,
 	.release = single_release,
 };

 static void vga_switcheroo_debugfs_fini(struct vgasr_priv *priv)
 {
 	if (priv->switch_file) {
 		debugfs_remove(priv->switch_file);
 		priv->switch_file = NULL;
 	}
 	if (priv->debugfs_root) {
 		debugfs_remove(priv->debugfs_root);
 		priv->debugfs_root = NULL;
 	}
 }

 static int vga_switcheroo_debugfs_init(struct vgasr_priv *priv)
 {
 	/* already initialised */
 	if (priv->debugfs_root)
 		return 0;
 	priv->debugfs_root = debugfs_create_dir("vgaswitcheroo", NULL);

 	if (!priv->debugfs_root) {
 		printk(KERN_ERR "vga_switcheroo: Cannot create /sys/kernel/debug/vgaswitcheroo\n");
 		goto fail;
 	}

 	priv->switch_file = debugfs_create_file("switch", 0644,
 						priv->debugfs_root, NULL, &vga_switcheroo_debugfs_fops);
 	if (!priv->switch_file) {
 		printk(KERN_ERR "vga_switcheroo: cannot create /sys/kernel/debug/vgaswitcheroo/switch\n");
 		goto fail;
 	}
 	return 0;
 fail:
 	vga_switcheroo_debugfs_fini(priv);
 	return -1;
 }

 int vga_switcheroo_process_delayed_switch(void)
 {
 	struct vga_switcheroo_client *client = NULL;
 	const char *pdev_name;
 	bool can_switch = true;
 	int i;
 	int ret;
 	int err = -EINVAL;

 	mutex_lock(&vgasr_mutex);
 	if (!vgasr_priv.delayed_switch_active)
 		goto err;

 	printk(KERN_INFO "vga_switcheroo: processing delayed switch to %d\n", vgasr_priv.delayed_client_id);

 	for (i = 0; i < VGA_SWITCHEROO_MAX_CLIENTS; i++) {
 		if (vgasr_priv.clients[i].id == vgasr_priv.delayed_client_id)
 			client = &vgasr_priv.clients[i];
 		can_switch = vgasr_priv.clients[i].can_switch(vgasr_priv.clients[i].pdev);
 		if (can_switch == false) {
 			printk(KERN_ERR "vga_switcheroo: client %d refused switch\n", i);
 			break;
 		}
 	}

 	if (can_switch == false || client == NULL)
 		goto err;

 	pdev_name = pci_name(client->pdev);
 	ret = vga_switchto(client);
 	if (ret)
 		printk(KERN_ERR "vga_switcheroo: delayed switching failed %d\n", ret);

 	vgasr_priv.delayed_switch_active = false;
 	err = 0;
 err:
 	mutex_unlock(&vgasr_mutex);
 	return err;
 }
 EXPORT_SYMBOL(vga_switcheroo_process_delayed_switch);
	/*
	* Copyright (c) 2010 Red Hat Inc.
	* Author : Dave Airlie <airlied@redhat.com>
	*
	*
	* Licensed under GPLv2
	*
	* vga_switcheroo.c - Support for laptop with dual GPU using one set of outputs

	Switcher interface - methods require for ATPX and DCM
	- switchto - this throws the output MUX switch
	- discrete_set_power - sets the power state for the discrete card

	GPU driver interface
	- set_gpu_state - this should do the equiv of s/r for the card
	- this should not set the discrete power state
	- switch_check - check if the device is in a position to switch now
	*/

	#include <linux/module.h>
	#include <linux/dmi.h>
	#include <linux/seq_file.h>
	#include <linux/uaccess.h>
	#include <linux/fs.h>
	#include <linux/debugfs.h>
	#include <linux/fb.h>

	#include <linux/pci.h>
	#include <linux/vga_switcheroo.h>

	struct vga_switcheroo_client {
	struct pci_dev *pdev;
	struct fb_info *fb_info;
	int pwr_state;
	void (set_gpu_state)(struct pci_dev pdev, enum vga_switcheroo_state);
	bool (can_switch)(struct pci_dev pdev);
	int id;
	bool active;
	};

	static DEFINE_MUTEX(vgasr_mutex);

	struct vgasr_priv {

	bool active;
	bool delayed_switch_active;
	enum vga_switcheroo_client_id delayed_client_id;

	struct dentry *debugfs_root;
	struct dentry *switch_file;

	int registered_clients;
	struct vga_switcheroo_client clients[VGA_SWITCHEROO_MAX_CLIENTS];

	struct vga_switcheroo_handler *handler;
	};

	static int vga_switcheroo_debugfs_init(struct vgasr_priv *priv);
	static void vga_switcheroo_debugfs_fini(struct vgasr_priv *priv);

	/* only one switcheroo per system */
	static struct vgasr_priv vgasr_priv;

	int vga_switcheroo_register_handler(struct vga_switcheroo_handler *handler)
	{
	mutex_lock(&vgasr_mutex);
	if (vgasr_priv.handler) {
	mutex_unlock(&vgasr_mutex);
	return -EINVAL;
	}

	vgasr_priv.handler = handler;
	mutex_unlock(&vgasr_mutex);
	return 0;
	}
	EXPORT_SYMBOL(vga_switcheroo_register_handler);

	void vga_switcheroo_unregister_handler(void)
	{
	mutex_lock(&vgasr_mutex);
	vgasr_priv.handler = NULL;
	mutex_unlock(&vgasr_mutex);
	}
	EXPORT_SYMBOL(vga_switcheroo_unregister_handler);

	static void vga_switcheroo_enable(void)
	{
	int i;
	int ret;
	/* call the handler to init */
	vgasr_priv.handler->init();

	for (i = 0; i < VGA_SWITCHEROO_MAX_CLIENTS; i++) {
	ret = vgasr_priv.handler->get_client_id(vgasr_priv.clients[i].pdev);
	if (ret < 0)
	return;

	vgasr_priv.clients[i].id = ret;
	}
	vga_switcheroo_debugfs_init(&vgasr_priv);
	vgasr_priv.active = true;
	}

	int vga_switcheroo_register_client(struct pci_dev *pdev,
	void (set_gpu_state)(struct pci_dev pdev, enum vga_switcheroo_state),
	bool (can_switch)(struct pci_dev pdev))
	{
	int index;

	mutex_lock(&vgasr_mutex);
	/* don't do IGD vs DIS here */
	if (vgasr_priv.registered_clients & 1)
	index = 1;
	else
	index = 0;

	vgasr_priv.clients[index].pwr_state = VGA_SWITCHEROO_ON;
	vgasr_priv.clients[index].pdev = pdev;
	vgasr_priv.clients[index].set_gpu_state = set_gpu_state;
	vgasr_priv.clients[index].can_switch = can_switch;
	vgasr_priv.clients[index].id = -1;
	if (pdev->resource[PCI_ROM_RESOURCE].flags & IORESOURCE_ROM_SHADOW)
	vgasr_priv.clients[index].active = true;

	vgasr_priv.registered_clients \|= (1 << index);

	/* if we get two clients + handler */
	if (vgasr_priv.registered_clients == 0x3 && vgasr_priv.handler) {
	printk(KERN_INFO "vga_switcheroo: enabled\n");
	vga_switcheroo_enable();
	}
	mutex_unlock(&vgasr_mutex);
	return 0;
	}
	EXPORT_SYMBOL(vga_switcheroo_register_client);

	void vga_switcheroo_unregister_client(struct pci_dev *pdev)
	{
	int i;

	mutex_lock(&vgasr_mutex);
	for (i = 0; i < VGA_SWITCHEROO_MAX_CLIENTS; i++) {
	if (vgasr_priv.clients[i].pdev == pdev) {
	vgasr_priv.registered_clients &= ~(1 << i);
	break;
	}
	}

	printk(KERN_INFO "vga_switcheroo: disabled\n");
	vga_switcheroo_debugfs_fini(&vgasr_priv);
	vgasr_priv.active = false;
	mutex_unlock(&vgasr_mutex);
	}
	EXPORT_SYMBOL(vga_switcheroo_unregister_client);

	void vga_switcheroo_client_fb_set(struct pci_dev *pdev,
	struct fb_info *info)
	{
	int i;

	mutex_lock(&vgasr_mutex);
	for (i = 0; i < VGA_SWITCHEROO_MAX_CLIENTS; i++) {
	if (vgasr_priv.clients[i].pdev == pdev) {
	vgasr_priv.clients[i].fb_info = info;
	break;
	}
	}
	mutex_unlock(&vgasr_mutex);
	}
	EXPORT_SYMBOL(vga_switcheroo_client_fb_set);

	static int vga_switcheroo_show(struct seq_file m, void v)
	{
	int i;
	mutex_lock(&vgasr_mutex);
	for (i = 0; i < VGA_SWITCHEROO_MAX_CLIENTS; i++) {
	seq_printf(m, "%d:%s:%c:%s:%s\n", i,
	vgasr_priv.clients[i].id == VGA_SWITCHEROO_DIS ? "DIS" : "IGD",
	vgasr_priv.clients[i].active ? '+' : ' ',
	vgasr_priv.clients[i].pwr_state ? "Pwr" : "Off",
	pci_name(vgasr_priv.clients[i].pdev));
	}
	mutex_unlock(&vgasr_mutex);
	return 0;
	}

	static int vga_switcheroo_debugfs_open(struct inode inode, struct file file)
	{
	return single_open(file, vga_switcheroo_show, NULL);
	}

	static int vga_switchon(struct vga_switcheroo_client *client)
	{
	int ret;

	ret = vgasr_priv.handler->power_state(client->id, VGA_SWITCHEROO_ON);
	/* call the driver callback to turn on device */
	client->set_gpu_state(client->pdev, VGA_SWITCHEROO_ON);
	client->pwr_state = VGA_SWITCHEROO_ON;
	return 0;
	}

	static int vga_switchoff(struct vga_switcheroo_client *client)
	{
	/* call the driver callback to turn off device */
	client->set_gpu_state(client->pdev, VGA_SWITCHEROO_OFF);
	vgasr_priv.handler->power_state(client->id, VGA_SWITCHEROO_OFF);
	client->pwr_state = VGA_SWITCHEROO_OFF;
	return 0;
	}

	static int vga_switchto(struct vga_switcheroo_client *new_client)
	{
	int ret;
	int i;
	struct vga_switcheroo_client *active = NULL;

	if (new_client->active == true)
	return 0;

	for (i = 0; i < VGA_SWITCHEROO_MAX_CLIENTS; i++) {
	if (vgasr_priv.clients[i].active == true) {
	active = &vgasr_priv.clients[i];
	break;
	}
	}
	if (!active)
	return 0;

	/* power up the first device */
	ret = pci_enable_device(new_client->pdev);
	if (ret)
	return ret;

	if (new_client->pwr_state == VGA_SWITCHEROO_OFF)
	vga_switchon(new_client);

	/* swap shadow resource to denote boot VGA device has changed so X starts on new device */
	active->active = false;

	active->pdev->resource[PCI_ROM_RESOURCE].flags &= ~IORESOURCE_ROM_SHADOW;
	new_client->pdev->resource[PCI_ROM_RESOURCE].flags \|= IORESOURCE_ROM_SHADOW;

	if (new_client->fb_info) {
	struct fb_event event;
	event.info = new_client->fb_info;
	fb_notifier_call_chain(FB_EVENT_REMAP_ALL_CONSOLE, &event);
	}

	ret = vgasr_priv.handler->switchto(new_client->id);
	if (ret)
	return ret;

	if (active->pwr_state == VGA_SWITCHEROO_ON)
	vga_switchoff(active);

	new_client->active = true;
	return 0;
	}

	static ssize_t
	vga_switcheroo_debugfs_write(struct file filp, const char __user ubuf,
	size_t cnt, loff_t *ppos)
	{
	char usercmd[64];
	const char *pdev_name;
	int i, ret;
	bool delay = false, can_switch;
	int client_id = -1;
	struct vga_switcheroo_client *client = NULL;

	if (cnt > 63)
	cnt = 63;

	if (copy_from_user(usercmd, ubuf, cnt))
	return -EFAULT;

	mutex_lock(&vgasr_mutex);

	if (!vgasr_priv.active) {
	cnt = -EINVAL;
	goto out;
	}

	/* pwr off the device not in use */
	if (strncmp(usercmd, "OFF", 3) == 0) {
	for (i = 0; i < VGA_SWITCHEROO_MAX_CLIENTS; i++) {
	if (vgasr_priv.clients[i].active)
	continue;
	if (vgasr_priv.clients[i].pwr_state == VGA_SWITCHEROO_ON)
	vga_switchoff(&vgasr_priv.clients[i]);
	}
	goto out;
	}
	/* pwr on the device not in use */
	if (strncmp(usercmd, "ON", 2) == 0) {
	for (i = 0; i < VGA_SWITCHEROO_MAX_CLIENTS; i++) {
	if (vgasr_priv.clients[i].active)
	continue;
	if (vgasr_priv.clients[i].pwr_state == VGA_SWITCHEROO_OFF)
	vga_switchon(&vgasr_priv.clients[i]);
	}
	goto out;
	}

	/* request a delayed switch - test can we switch now */
	if (strncmp(usercmd, "DIGD", 4) == 0) {
	client_id = VGA_SWITCHEROO_IGD;
	delay = true;
	}

	if (strncmp(usercmd, "DDIS", 4) == 0) {
	client_id = VGA_SWITCHEROO_DIS;
	delay = true;
	}

	if (strncmp(usercmd, "IGD", 3) == 0)
	client_id = VGA_SWITCHEROO_IGD;

	if (strncmp(usercmd, "DIS", 3) == 0)
	client_id = VGA_SWITCHEROO_DIS;

	if (client_id == -1)
	goto out;

	for (i = 0; i < VGA_SWITCHEROO_MAX_CLIENTS; i++) {
	if (vgasr_priv.clients[i].id == client_id) {
	client = &vgasr_priv.clients[i];
	break;
	}
	}

	vgasr_priv.delayed_switch_active = false;
	/* okay we want a switch - test if devices are willing to switch */
	can_switch = true;
	for (i = 0; i < VGA_SWITCHEROO_MAX_CLIENTS; i++) {
	can_switch = vgasr_priv.clients[i].can_switch(vgasr_priv.clients[i].pdev);
	if (can_switch == false) {
	printk(KERN_ERR "vga_switcheroo: client %d refused switch\n", i);
	break;
	}
	}

	if (can_switch == false && delay == false)
	goto out;

	if (can_switch == true) {
	pdev_name = pci_name(client->pdev);
	ret = vga_switchto(client);
	if (ret)
	printk(KERN_ERR "vga_switcheroo: switching failed %d\n", ret);
	} else {
	printk(KERN_INFO "vga_switcheroo: setting delayed switch to client %d\n", client->id);
	vgasr_priv.delayed_switch_active = true;
	vgasr_priv.delayed_client_id = client_id;

	/* we should at least power up the card to
	make the switch faster */
	if (client->pwr_state == VGA_SWITCHEROO_OFF)
	vga_switchon(client);
	}

	out:
	mutex_unlock(&vgasr_mutex);
	return cnt;
	}

	static const struct file_operations vga_switcheroo_debugfs_fops = {
	.owner = THIS_MODULE,
	.open = vga_switcheroo_debugfs_open,
	.write = vga_switcheroo_debugfs_write,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = single_release,
	};

	static void vga_switcheroo_debugfs_fini(struct vgasr_priv *priv)
	{
	if (priv->switch_file) {
	debugfs_remove(priv->switch_file);
	priv->switch_file = NULL;
	}
	if (priv->debugfs_root) {
	debugfs_remove(priv->debugfs_root);
	priv->debugfs_root = NULL;
	}
	}

	static int vga_switcheroo_debugfs_init(struct vgasr_priv *priv)
	{
	/* already initialised */
	if (priv->debugfs_root)
	return 0;
	priv->debugfs_root = debugfs_create_dir("vgaswitcheroo", NULL);

	if (!priv->debugfs_root) {
	printk(KERN_ERR "vga_switcheroo: Cannot create /sys/kernel/debug/vgaswitcheroo\n");
	goto fail;
	}

	priv->switch_file = debugfs_create_file("switch", 0644,
	priv->debugfs_root, NULL, &vga_switcheroo_debugfs_fops);
	if (!priv->switch_file) {
	printk(KERN_ERR "vga_switcheroo: cannot create /sys/kernel/debug/vgaswitcheroo/switch\n");
	goto fail;
	}
	return 0;
	fail:
	vga_switcheroo_debugfs_fini(priv);
	return -1;
	}

	int vga_switcheroo_process_delayed_switch(void)
	{
	struct vga_switcheroo_client *client = NULL;
	const char *pdev_name;
	bool can_switch = true;
	int i;
	int ret;
	int err = -EINVAL;

	mutex_lock(&vgasr_mutex);
	if (!vgasr_priv.delayed_switch_active)
	goto err;

	printk(KERN_INFO "vga_switcheroo: processing delayed switch to %d\n", vgasr_priv.delayed_client_id);

	for (i = 0; i < VGA_SWITCHEROO_MAX_CLIENTS; i++) {
	if (vgasr_priv.clients[i].id == vgasr_priv.delayed_client_id)
	client = &vgasr_priv.clients[i];
	can_switch = vgasr_priv.clients[i].can_switch(vgasr_priv.clients[i].pdev);
	if (can_switch == false) {
	printk(KERN_ERR "vga_switcheroo: client %d refused switch\n", i);
	break;
	}
	}

	if (can_switch == false \|\| client == NULL)
	goto err;

	pdev_name = pci_name(client->pdev);
	ret = vga_switchto(client);
	if (ret)
	printk(KERN_ERR "vga_switcheroo: delayed switching failed %d\n", ret);

	vgasr_priv.delayed_switch_active = false;
	err = 0;
	err:
	mutex_unlock(&vgasr_mutex);
	return err;
	}
	EXPORT_SYMBOL(vga_switcheroo_process_delayed_switch);