[PATCH 1/2] vga: implements VGA arbitration on Linux

[Tiago Vignatti <tiago.vignatti@nokia.com>]

Signed-off-by: Tiago Vignatti <tiago.vignatti@nokia.com>
---
 drivers/gpu/Makefile     |    2 +-
 drivers/gpu/vga/Kconfig  |    8 +
 drivers/gpu/vga/Makefile |    1 +
 drivers/gpu/vga/vgaarb.c | 1120 ++++++++++++++++++++++++++++++++++++++++++++++
 drivers/gpu/vga/vgaarb.h |  168 +++++++
 drivers/video/Kconfig    |    2 +
 6 files changed, 1300 insertions(+), 1 deletions(-)
 create mode 100644 drivers/gpu/vga/Kconfig
 create mode 100644 drivers/gpu/vga/Makefile
 create mode 100644 drivers/gpu/vga/vgaarb.c
 create mode 100644 drivers/gpu/vga/vgaarb.h

diff --git a/drivers/gpu/Makefile b/drivers/gpu/Makefile
index de566cf..30879df 100644
--- a/drivers/gpu/Makefile
+++ b/drivers/gpu/Makefile
@@ -1 +1 @@
-obj-y			+= drm/
+obj-y			+= drm/ vga/
diff --git a/drivers/gpu/vga/Kconfig b/drivers/gpu/vga/Kconfig
new file mode 100644
index 0000000..06e0ab4
--- /dev/null
+++ b/drivers/gpu/vga/Kconfig
@@ -0,0 +1,8 @@
+config VGA_ARB
+	tristate "VGA arbitration"
+	help
+	  Some "legacy" VGA devices implemented on PCI typically have the same
+	  hard-decoded addresses as they did on ISA. When multiple PCI devices
+	  are accessed at same time they need some kind of coordination. Please
+	  see Documentation/vgaarbiter.txt for more details. Select this to
+	  enable VGA arbiter.
diff --git a/drivers/gpu/vga/Makefile b/drivers/gpu/vga/Makefile
new file mode 100644
index 0000000..7cc8c1e
--- /dev/null
+++ b/drivers/gpu/vga/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_VGA_ARB)  += vgaarb.o
diff --git a/drivers/gpu/vga/vgaarb.c b/drivers/gpu/vga/vgaarb.c
new file mode 100644
index 0000000..db89eee
--- /dev/null
+++ b/drivers/gpu/vga/vgaarb.c
@@ -0,0 +1,1120 @@
+/*
+ * vgaarb.c
+ *
+ * (C) Copyright 2005 Benjamin Herrenschmidt <benh@kernel.crashing.org>
+ * (C) Copyright 2007 Paulo R. Zanoni <przanoni@gmail.com>
+ * (C) Copyright 2007, 2009 Tiago Vignatti <vignatti@freedesktop.org>
+ *
+ * Implements the VGA arbitration. For details refer to
+ * Documentation/vgaarbiter.txt
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/pci.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/list.h>
+#include <linux/sched.h>
+#include <linux/wait.h>
+#include <linux/spinlock.h>
+#include <linux/poll.h>
+#include <linux/miscdevice.h>
+
+#include <linux/uaccess.h>
+
+#include "vgaarb.h"
+
+/*
+ * We keep a list of all vga devices in the system to speed
+ * up the various operations of the arbiter
+ */
+struct vga_device {
+	struct list_head list;
+	struct pci_dev *pdev;
+	unsigned int decodes;	/* what does it decodes */
+	unsigned int owns;	/* what does it owns */
+	unsigned int locks;	/* what does it locks */
+	unsigned int io_lock_cnt;	/* legacy IO lock count */
+	unsigned int mem_lock_cnt;	/* legacy MEM lock count */
+	unsigned int io_norm_cnt;	/* normal IO count */
+	unsigned int mem_norm_cnt;	/* normal MEM count */
+};
+
+static LIST_HEAD(vga_list);
+static DEFINE_SPINLOCK(vga_lock);
+static DECLARE_WAIT_QUEUE_HEAD(vga_wait_queue);
+
+#ifndef __ARCH_HAS_VGA_DEFAULT_DEVICE
+static struct pci_dev *vga_default;
+#endif
+
+static void vga_arb_device_card_gone(struct pci_dev *pdev);
+
+/* Find somebody in our list */
+static struct vga_device *vgadev_find(struct pci_dev *pdev)
+{
+	struct vga_device *vgadev;
+
+	list_for_each_entry(vgadev, &vga_list, list)
+	    if (pdev == vgadev->pdev)
+		return vgadev;
+	return NULL;
+}
+
+/* Returns the default VGA device (vgacon's babe) */
+#ifndef __ARCH_HAS_VGA_DEFAULT_DEVICE
+struct pci_dev *vga_default_device(void)
+{
+	return vga_default;
+}
+#endif
+
+/* Architecture can override enabling/disabling of a given
+ * device resources here
+ *
+ * TODO: <benh>  you can try to be "smart" and if for example you have 2 cards
+ * that are behind separate bridges, you need only swapping the bridge controls
+ * and you can keep the card master IO and memory enable.
+ */
+#ifndef __ARCH_HAS_VGA_DISABLE_RESOURCES
+static inline void vga_disable_resources(struct pci_dev *pdev,
+					 unsigned int rsrc,
+					 unsigned int change_bridge)
+{
+	struct pci_bus *bus;
+	struct pci_dev *bridge;
+	u16 cmd;
+
+#ifdef DEBUG
+	printk(KERN_DEBUG "%s\n", __func__);
+#endif
+	pci_read_config_word(pdev, PCI_COMMAND, &cmd);
+	if (rsrc & (VGA_RSRC_LEGACY_IO | VGA_RSRC_NORMAL_IO))
+		cmd &= ~PCI_COMMAND_IO;
+	if (rsrc & (VGA_RSRC_LEGACY_MEM | VGA_RSRC_NORMAL_MEM))
+		cmd &= ~PCI_COMMAND_MEMORY;
+	pci_write_config_word(pdev, PCI_COMMAND, cmd);
+
+	if (!change_bridge)
+		return;
+
+	bus = pdev->bus;
+	while (bus) {
+		bridge = bus->self;
+		if (bridge) {
+			pci_read_config_word(bridge, PCI_BRIDGE_CONTROL,
+					     &cmd);
+			if (cmd & PCI_BRIDGE_CTL_VGA) {
+				cmd &= ~PCI_BRIDGE_CTL_VGA;
+				pci_write_config_word(bridge,
+						      PCI_BRIDGE_CONTROL,
+						      cmd);
+			}
+		}
+		bus = bus->parent;
+	}
+}
+#endif
+
+#ifndef __ARCH_HAS_VGA_ENABLE_RESOURCES
+static inline void vga_enable_resources(struct pci_dev *pdev,
+					unsigned int rsrc)
+{
+	struct pci_bus *bus;
+	struct pci_dev *bridge;
+	u16 cmd;
+
+#ifdef DEBUG
+	printk(KERN_DEBUG "%s\n", __func__);
+#endif
+	pci_read_config_word(pdev, PCI_COMMAND, &cmd);
+	if (rsrc & (VGA_RSRC_LEGACY_IO | VGA_RSRC_NORMAL_IO))
+		cmd |= PCI_COMMAND_IO;
+	if (rsrc & (VGA_RSRC_LEGACY_MEM | VGA_RSRC_NORMAL_MEM))
+		cmd |= PCI_COMMAND_MEMORY;
+	pci_write_config_word(pdev, PCI_COMMAND, cmd);
+
+	if (!(rsrc & VGA_RSRC_LEGACY_MASK))
+		return;
+
+	bus = pdev->bus;
+	while (bus) {
+		bridge = bus->self;
+		if (bridge) {
+			pci_read_config_word(bridge, PCI_BRIDGE_CONTROL,
+					     &cmd);
+			if (!(cmd & PCI_BRIDGE_CTL_VGA)) {
+				cmd |= PCI_BRIDGE_CTL_VGA;
+				pci_write_config_word(bridge,
+						      PCI_BRIDGE_CONTROL,
+						      cmd);
+			}
+		}
+		bus = bus->parent;
+	}
+}
+#endif
+
+static struct vga_device *__vga_tryget(struct vga_device *vgadev,
+				       unsigned int rsrc)
+{
+	unsigned int wants, legacy_wants, match;
+	struct vga_device *conflict;
+
+	/* Account for "normal" resources to lock. If we decode the legacy,
+	 * counterpart, we need to request it as well
+	 */
+	if ((rsrc & VGA_RSRC_NORMAL_IO) &&
+	    (vgadev->decodes & VGA_RSRC_LEGACY_IO))
+		rsrc |= VGA_RSRC_LEGACY_IO;
+	if ((rsrc & VGA_RSRC_NORMAL_MEM) &&
+	    (vgadev->decodes & VGA_RSRC_LEGACY_MEM))
+		rsrc |= VGA_RSRC_LEGACY_MEM;
+
+#ifdef DEBUG
+	printk(KERN_DEBUG "%s: %d\n", __func__, rsrc);
+	printk(KERN_DEBUG "%s: owns: %d\n", __func__, vgadev->owns);
+#endif
+
+	/* Check what resources we need to acquire */
+	wants = rsrc & ~vgadev->owns;
+
+	/* We already own everything, just mark locked & bye bye */
+	if (wants == 0)
+		goto lock_them;
+
+	/* We don't need to request a legacy resource, we just enable
+	 * appropriate decoding and go
+	 */
+	legacy_wants = wants & VGA_RSRC_LEGACY_MASK;
+	if (legacy_wants == 0)
+		goto enable_them;
+
+	/* Ok, we don't, let's find out how we need to kick off */
+	list_for_each_entry(conflict, &vga_list, list) {
+		unsigned int lwants = legacy_wants;
+		unsigned int change_bridge = 0;
+
+		/* Don't conflict with myself */
+		if (vgadev == conflict)
+			continue;
+
+		/* Check if the architecture allows a conflict between those
+		 * 2 devices or if they are on separate domains
+		 */
+		if (!vga_conflicts(vgadev->pdev, conflict->pdev))
+			continue;
+
+		/* We have a possible conflict. before we go further, we must
+		 * check if we sit on the same bus as the conflicting device.
+		 * if we don't, then we must tie both IO and MEM resources
+		 * together since there is only a single bit controlling
+		 * VGA forwarding on P2P bridges
+		 */
+		if (vgadev->pdev->bus != conflict->pdev->bus) {
+			change_bridge = 1;
+			lwants = VGA_RSRC_LEGACY_IO | VGA_RSRC_LEGACY_MEM;
+		}
+
+		/* Check if the guy has a lock on the resource. If he does,
+		 * return the conflicting entry
+		 */
+		if (conflict->locks & lwants)
+			return conflict;
+
+		/* Ok, now check if he owns the resource we want. We don't need
+		 * to check "decodes" since it should be impossible to own
+		 * own legacy resources you don't decode unless I have a bug
+		 * in this code...
+		 */
+		WARN_ON(conflict->owns & ~conflict->decodes);
+		match = lwants & conflict->owns;
+		if (!match)
+			continue;
+
+		/* looks like he doesn't have a lock, we can steal
+		 * them from him
+		 */
+		vga_disable_resources(conflict->pdev, lwants,
+				      change_bridge);
+		conflict->owns &= ~lwants;
+		/* If he also owned non-legacy, that is no longer the case */
+		if (lwants & VGA_RSRC_LEGACY_MEM)
+			conflict->owns &= ~VGA_RSRC_NORMAL_MEM;
+		if (lwants & VGA_RSRC_LEGACY_IO)
+			conflict->owns &= ~VGA_RSRC_NORMAL_IO;
+	}
+
+enable_them:
+	/* ok dude, we got it, everybody conflicting has been disabled, let's
+	 * enable us. Make sure we don't mark a bit in "owns" that we don't
+	 * also have in "decodes". We can lock resources we don't decode but
+	 * not own them.
+	 */
+	vga_enable_resources(vgadev->pdev, wants);
+	vgadev->owns |= (wants & vgadev->decodes);
+lock_them:
+	vgadev->locks |= (rsrc & VGA_RSRC_LEGACY_MASK);
+	if (rsrc & VGA_RSRC_LEGACY_IO)
+		vgadev->io_lock_cnt++;
+	if (rsrc & VGA_RSRC_LEGACY_MEM)
+		vgadev->mem_lock_cnt++;
+	if (rsrc & VGA_RSRC_NORMAL_IO)
+		vgadev->io_norm_cnt++;
+	if (rsrc & VGA_RSRC_NORMAL_MEM)
+		vgadev->mem_norm_cnt++;
+
+	return NULL;
+}
+
+static void __vga_put(struct vga_device *vgadev, unsigned int rsrc)
+{
+	unsigned int old_locks = vgadev->locks;
+
+#ifdef DEBUG
+	printk(KERN_DEBUG "%s\n", __func__);
+#endif
+
+	/* Update our counters, and account for equivalent legacy resources
+	 * if we decode them
+	 */
+	if ((rsrc & VGA_RSRC_NORMAL_IO) && vgadev->io_norm_cnt > 0) {
+		vgadev->io_norm_cnt--;
+		if (vgadev->decodes & VGA_RSRC_LEGACY_IO)
+			rsrc |= VGA_RSRC_LEGACY_IO;
+	}
+	if ((rsrc & VGA_RSRC_NORMAL_MEM) && vgadev->mem_norm_cnt > 0) {
+		vgadev->mem_norm_cnt--;
+		if (vgadev->decodes & VGA_RSRC_LEGACY_MEM)
+			rsrc |= VGA_RSRC_LEGACY_MEM;
+	}
+	if ((rsrc & VGA_RSRC_LEGACY_IO) && vgadev->io_lock_cnt > 0)
+		vgadev->io_lock_cnt--;
+	if ((rsrc & VGA_RSRC_LEGACY_MEM) && vgadev->mem_lock_cnt > 0)
+		vgadev->mem_lock_cnt--;
+
+	/* Just clear lock bits, we do lazy operations so we don't really
+	 * have to bother about anything else at this point
+	 */
+	if (vgadev->io_lock_cnt == 0)
+		vgadev->locks &= ~VGA_RSRC_LEGACY_IO;
+	if (vgadev->mem_lock_cnt == 0)
+		vgadev->locks &= ~VGA_RSRC_LEGACY_MEM;
+
+	/* Kick the wait queue in case somebody was waiting if we actually
+	 * released something
+	 */
+	if (old_locks != vgadev->locks)
+		wake_up_all(&vga_wait_queue);
+}
+
+int vga_get(struct pci_dev *pdev, unsigned int rsrc, int interruptible)
+{
+	struct vga_device *vgadev, *conflict;
+	unsigned long flags;
+	wait_queue_t wait;
+	int rc = 0;
+
+	/* The one who calls us should check for this, but lets be sure... */
+	if (pdev == NULL)
+		pdev = vga_default_device();
+	if (pdev == NULL)
+		return 0;
+
+	for (;;) {
+		spin_lock_irqsave(&vga_lock, flags);
+		vgadev = vgadev_find(pdev);
+		if (vgadev == NULL) {
+			spin_unlock_irqrestore(&vga_lock, flags);
+			rc = -ENODEV;
+			break;
+		}
+		conflict = __vga_tryget(vgadev, rsrc);
+		spin_unlock_irqrestore(&vga_lock, flags);
+		if (conflict == NULL)
+			break;
+
+
+		/* We have a conflict, we wait until somebody kicks the
+		 * work queue. Currently we have one work queue that we
+		 * kick each time some resources are released, but it would
+		 * be fairly easy to have a per device one so that we only
+		 * need to attach to the conflicting device
+		 */
+		init_waitqueue_entry(&wait, current);
+		add_wait_queue(&vga_wait_queue, &wait);
+		set_current_state(interruptible ?
+				  TASK_INTERRUPTIBLE :
+				  TASK_UNINTERRUPTIBLE);
+		if (signal_pending(current)) {
+			rc = -EINTR;
+			break;
+		}
+		schedule();
+		remove_wait_queue(&vga_wait_queue, &wait);
+		set_current_state(TASK_RUNNING);
+	}
+	return rc;
+}
+
+int vga_tryget(struct pci_dev *pdev, unsigned int rsrc)
+{
+	struct vga_device *vgadev;
+	unsigned long flags;
+	int rc = 0;
+
+	/* The one who calls us should check for this, but lets be sure... */
+	if (pdev == NULL)
+		pdev = vga_default_device();
+	if (pdev == NULL)
+		return 0;
+	spin_lock_irqsave(&vga_lock, flags);
+	vgadev = vgadev_find(pdev);
+	if (vgadev == NULL) {
+		rc = -ENODEV;
+		goto bail;
+	}
+	if (__vga_tryget(vgadev, rsrc))
+		rc = -EBUSY;
+bail:
+	spin_unlock_irqrestore(&vga_lock, flags);
+	return rc;
+}
+
+void vga_put(struct pci_dev *pdev, unsigned int rsrc)
+{
+	struct vga_device *vgadev;
+	unsigned long flags;
+
+	/* The one who calls us should check for this, but lets be sure... */
+	if (pdev == NULL)
+		pdev = vga_default_device();
+	if (pdev == NULL)
+		return;
+	spin_lock_irqsave(&vga_lock, flags);
+	vgadev = vgadev_find(pdev);
+	if (vgadev == NULL)
+		goto bail;
+	__vga_put(vgadev, rsrc);
+bail:
+	spin_unlock_irqrestore(&vga_lock, flags);
+}
+
+/*
+ * Currently, we assume that the "initial" setup of the system is
+ * not sane, that is we come up with conflicting devices and let
+ * the arbiter's client decides if devices decodes or not legacy
+ * things.
+ */
+static void vga_arbiter_add_pci_device(struct pci_dev *pdev)
+{
+	struct vga_device *vgadev;
+	unsigned long flags;
+	struct pci_bus *bus;
+	struct pci_dev *bridge;
+	u16 cmd;
+
+	/* Only deal with VGA class devices */
+	if ((pdev->class >> 8) != PCI_CLASS_DISPLAY_VGA)
+		return;
+
+	/* Allocate structure */
+	vgadev = kmalloc(sizeof(struct vga_device), GFP_KERNEL);
+	if (vgadev == NULL) {
+		/* What to do on allocation failure ? For now, let's
+		 * just do nothing, I'm not sure there is anything saner
+		 * to be done
+		 */
+		return;
+	}
+
+	memset(vgadev, 0, sizeof(*vgadev));
+
+	/* Take lock & check for duplicates */
+	spin_lock_irqsave(&vga_lock, flags);
+	if (vgadev_find(pdev) != NULL) {
+		BUG_ON(1);
+		goto fail;
+	}
+	vgadev->pdev = pdev;
+
+	/* By default, assume we decode everything */
+	vgadev->decodes = VGA_RSRC_LEGACY_IO | VGA_RSRC_LEGACY_MEM |
+	    VGA_RSRC_NORMAL_IO | VGA_RSRC_NORMAL_MEM;
+
+	/* Mark that we "own" resources based on our enables, we will
+	 * clear that below if the bridge isn't forwarding
+	 */
+	pci_read_config_word(pdev, PCI_COMMAND, &cmd);
+	if (cmd & PCI_COMMAND_IO)
+		vgadev->owns |= VGA_RSRC_LEGACY_IO;
+	if (cmd & PCI_COMMAND_MEMORY)
+		vgadev->owns |= VGA_RSRC_LEGACY_MEM;
+
+	/* Check if VGA cycles can get down to us */
+	bus = pdev->bus;
+	while (bus) {
+		bridge = bus->self;
+		if (bridge) {
+			u16 l;
+			pci_read_config_word(bridge, PCI_BRIDGE_CONTROL,
+					     &l);
+			if (!(l & PCI_BRIDGE_CTL_VGA)) {
+				vgadev->owns = 0;
+				break;
+			}
+		}
+		bus = bus->parent;
+	}
+
+	/* Deal with VGA default device. Use first enabled one
+	 * by default if arch doesn't have it's own hook
+	 */
+#ifndef __ARCH_HAS_VGA_DEFAULT_DEVICE
+	if (vga_default == NULL && (vgadev->owns & VGA_RSRC_LEGACY_MEM) &&
+	    (vgadev->owns & VGA_RSRC_LEGACY_IO))
+		vga_default = pdev;
+
+#endif
+
+	/* Add to the list */
+	list_add(&vgadev->list, &vga_list);
+	printk(KERN_INFO "VGA Arbiter: device added: %d %d %d\n",
+						pdev->device, pdev->vendor, pdev->devfn);
+	spin_unlock_irqrestore(&vga_lock, flags);
+	return;
+fail:
+	spin_unlock_irqrestore(&vga_lock, flags);
+	kfree(vgadev);
+}
+
+static void vga_arbiter_del_pci_device(struct pci_dev *pdev)
+{
+	struct vga_device *vgadev;
+	unsigned long flags;
+
+	spin_lock_irqsave(&vga_lock, flags);
+	vgadev = vgadev_find(pdev);
+	if (vgadev == NULL)
+		goto bail;
+
+	/* Remove entry from list */
+	list_del(&vgadev->list);
+
+	/* Notify userland driver that the device is gone so it discards
+	 * it's copies of the pci_dev pointer
+	 */
+	vga_arb_device_card_gone(pdev);
+
+	/* Wake up all possible waiters */
+	wake_up_all(&vga_wait_queue);
+bail:
+	spin_unlock_irqrestore(&vga_lock, flags);
+	kfree(vgadev);
+}
+
+void vga_set_legacy_decoding(struct pci_dev *pdev, unsigned int decodes)
+{
+	struct vga_device *vgadev;
+	unsigned long flags;
+
+	decodes &= VGA_RSRC_LEGACY_MASK;
+
+	spin_lock_irqsave(&vga_lock, flags);
+	vgadev = vgadev_find(pdev);
+	if (vgadev == NULL)
+		goto bail;
+
+	vgadev->decodes = decodes;
+	vgadev->owns &= decodes;
+
+	/* XXX if somebody is going from "doesn't decode" to "decodes" state
+	 * here, additional care must be taken as we may have pending owner
+	 * ship of non-legacy region ...
+	 */
+bail:
+	spin_unlock_irqrestore(&vga_lock, flags);
+}
+
+
+/*
+ * Char driver implementation
+ *
+ * Semantics is:
+ *
+ *  open       : open user instance of the arbitrer. by default, it's
+ *                attached to the default VGA device of the system.
+ *
+ *  close      : close user instance, release locks
+ *
+ *  read       : return a string indicating the status of the target.
+ *                an IO state string is of the form {io,mem,io+mem,none},
+ *                mc and ic are respectively mem and io lock counts (for
+ *                debugging/diagnostic only). "decodes" indicate what the
+ *                card currently decodes, "owns" indicates what is currently
+ *                enabled on it, and "locks" indicates what is locked by this
+ *                card. If the card is unplugged, we get "invalid" then for
+ *                card_ID and an -ENODEV error is returned for any command
+ *                until a new card is targeted
+ *
+ *   "<card_ID>,decodes=<io_state>,owns=<io_state>,locks=<io_state> (ic,mc)"
+ *
+ * write       : write a command to the arbiter. List of commands is:
+ *
+ *   target <card_ID>   : switch target to card <card_ID> (see below)
+ *   lock <io_state>    : acquires locks on target ("none" is invalid io_state)
+ *   trylock <io_state> : non-blocking acquire locks on target
+ *   unlock <io_state>  : release locks on target
+ *   unlock all         : release all locks on target held by this user
+ *   decodes <io_state> : set the legacy decoding attributes for the card
+ *
+ * poll         : event if something change on any card (not just the target)
+ *
+ * card_ID is of the form "PCI:domain:bus:dev.fn". It can be set to "default"
+ * to go back to the system default card (TODO: not implemented yet).
+ * Currently, only PCI is supported as a prefix, but the userland API may
+ * support other bus types in the future, even if the current kernel
+ * implementation doesn't.
+ *
+ * Note about locks:
+ *
+ * The driver keeps track of which user has what locks on which card. It
+ * supports stacking, like the kernel one. This complexifies the implementation
+ * a bit, but makes the arbiter more tolerant to userspace problems and able
+ * to properly cleanup in all cases when a process dies.
+ * Currently, a max of 16 cards simultaneously can have locks issued from
+ * userspace for a given user (file descriptor instance) of the arbiter.
+ *
+ * If the device is hot-unplugged, there is a hook inside the module to notify
+ * they being added/removed in the system and automatically added/removed in
+ * the arbiter.
+ */
+
+#define MAX_USER_CARDS         16
+#define PCI_INVALID_CARD       ((struct pci_dev *)-1UL)
+
+/*
+ * Each user has an array of these, tracking which cards have locks
+ */
+struct vga_arb_user_card {
+	struct pci_dev *pdev;
+	unsigned int mem_cnt;
+	unsigned int io_cnt;
+};
+
+struct vga_arb_private {
+	struct list_head list;
+	struct pci_dev *target;
+	struct vga_arb_user_card cards[MAX_USER_CARDS];
+	spinlock_t lock;
+};
+
+static LIST_HEAD(vga_user_list);
+static DEFINE_SPINLOCK(vga_user_lock);
+
+static const char *vga_iostate_to_str(unsigned int iostate)
+{
+	/* Ignore VGA_RSRC_IO and VGA_RSRC_MEM */
+	iostate &= VGA_RSRC_LEGACY_IO | VGA_RSRC_LEGACY_MEM;
+	switch (iostate) {
+	case VGA_RSRC_LEGACY_IO | VGA_RSRC_LEGACY_MEM:
+		return "io+mem";
+	case VGA_RSRC_LEGACY_IO:
+		return "io";
+	case VGA_RSRC_LEGACY_MEM:
+		return "mem";
+	}
+	return "none";
+}
+
+static int vga_str_to_iostate(char *buf, int str_size, int *io_state)
+{
+	/* XXX We're not chekcing the str_size! */
+	if (strncmp(buf, "io+mem", 6) == 0)
+		*io_state = VGA_RSRC_LEGACY_IO | VGA_RSRC_LEGACY_MEM;
+	else if (strncmp(buf, "io", 2) == 0)
+		*io_state = VGA_RSRC_LEGACY_IO;
+	else if (strncmp(buf, "mem", 3) == 0)
+		*io_state = VGA_RSRC_LEGACY_MEM;
+	else if (strncmp(buf, "none", 4) == 0)
+		*io_state = VGA_RSRC_NONE;
+	else
+		return 0;
+	return 1;
+}
+
+/*
+ * This function gets a string in the format: "PCI:domain:bus:dev.fn" and
+ * returns the respective values. If the string is not in this format,
+ * it returns 0.
+ */
+static int vga_pci_str_to_vars(char *buf, int count, unsigned int *domain,
+			       unsigned int *bus, unsigned int *devfn)
+{
+	int n;
+	unsigned int slot, func;
+
+	n = sscanf(buf, "PCI:%d:%d:%d.%d", domain, bus, &slot, &func);
+	if (n != 4)
+		return 0;
+
+	*devfn = PCI_DEVFN(slot, func);
+
+	return 1;
+}
+
+static ssize_t vga_arb_read(struct file *file, char __user * buf,
+			    size_t count, loff_t *ppos)
+{
+	struct vga_arb_private *priv = file->private_data;
+	struct vga_device *vgadev;
+	struct pci_dev *pdev;
+	unsigned long flags;
+	size_t len;
+	int rc;
+	char *lbuf;
+
+#ifdef DEBUG
+	printk(KERN_DEBUG "vga_arb_read()\n");
+#endif
+	lbuf = kmalloc(1024, GFP_KERNEL);
+	if (lbuf == NULL)
+		return -ENOMEM;
+
+	/* Shields against vga_arb_device_card_gone (pci_dev going
+	 * away), and allows access to vga list
+	 */
+	spin_lock_irqsave(&vga_lock, flags);
+
+	/* If we are targetting the default, use it */
+	pdev = priv->target;
+	if (pdev == NULL || pdev == PCI_INVALID_CARD) {
+		spin_unlock_irqrestore(&vga_lock, flags);
+		len = sprintf(lbuf, "invalid");
+		goto done;
+	}
+
+	/* Find card vgadev structure */
+	vgadev = vgadev_find(pdev);
+	if (vgadev == NULL) {
+		/* Wow, it's not in the list, that shouldn't happen,
+		 * let's fix us up and return invalid card
+		 */
+		if (pdev == priv->target)
+			vga_arb_device_card_gone(pdev);
+		spin_unlock_irqrestore(&vga_lock, flags);
+		len = sprintf(lbuf, "invalid");
+		goto done;
+	}
+
+	/* Fill the buffer with infos */
+	len = snprintf(lbuf, 1024,
+		       "PCI:%s,decodes=%s,owns=%s,locks=%s (%d,%d)\n",
+		       pci_name(pdev),
+		       vga_iostate_to_str(vgadev->decodes),
+		       vga_iostate_to_str(vgadev->owns),
+		       vga_iostate_to_str(vgadev->locks),
+		       vgadev->io_lock_cnt, vgadev->mem_lock_cnt);
+
+	spin_unlock_irqrestore(&vga_lock, flags);
+done:
+
+	/* Copy that to user */
+	if (len > count)
+		len = count;
+	rc = copy_to_user(buf, lbuf, len);
+	kfree(lbuf);
+	if (rc)
+		return -EFAULT;
+	return len;
+}
+
+/*
+ * TODO: To avoid parsing inside kernel and to improve the speed we may
+ * consider use ioctl here
+ */
+static ssize_t vga_arb_write(struct file *file, const char __user * buf,
+			     size_t count, loff_t *ppos)
+{
+	struct vga_arb_private *priv = file->private_data;
+	struct pci_dev *pdev;
+
+	unsigned int io_state;
+
+	char *kbuf, *curr_pos;
+	size_t remaining = count;
+
+	int ret_val;
+	int i;
+
+
+	kbuf = kmalloc(count + 1, GFP_KERNEL);
+	if (!kbuf)
+		return -ENOMEM;
+
+	if (copy_from_user(kbuf, buf, count)) {
+		kfree(kbuf);
+		return -EFAULT;
+	}
+	curr_pos = kbuf;
+	kbuf[count] = '\0';	/* Just to make sure... */
+
+	if (strncmp(curr_pos, "lock ", 5) == 0) {
+		curr_pos += 5;
+		remaining -= 5;
+#ifdef DEBUG
+		printk(KERN_DEBUG "client 0x%X called 'lock'\n", (int)priv);
+#endif
+
+		if (!vga_str_to_iostate(curr_pos, remaining, &io_state)) {
+			ret_val = -EPROTO;
+			goto done;
+		}
+		if (io_state == VGA_RSRC_NONE) {
+			ret_val = -EPROTO;
+			goto done;
+		}
+
+		pdev = priv->target;
+		if (priv->target == NULL) {
+				ret_val = -ENODEV;
+			goto done;
+		}
+
+		vga_get_uninterruptible(pdev, io_state);
+
+		/* Update the client's locks lists... */
+		for (i = 0; i < MAX_USER_CARDS; i++) {
+			if (priv->cards[i].pdev == pdev) {
+				if (io_state & VGA_RSRC_LEGACY_IO)
+					priv->cards[i].io_cnt++;
+				if (io_state & VGA_RSRC_LEGACY_MEM)
+					priv->cards[i].mem_cnt++;
+				break;
+			}
+		}
+
+		ret_val = count;
+		goto done;
+	} else if (strncmp(curr_pos, "unlock ", 7) == 0) {
+		curr_pos += 7;
+		remaining -= 7;
+#ifdef DEBUG
+		printk(KERN_DEBUG "client 0x%X called 'unlock'\n", (int)priv);
+#endif
+
+		if (strncmp(curr_pos, "all", 3) == 0)
+			io_state = VGA_RSRC_LEGACY_IO | VGA_RSRC_LEGACY_MEM;
+		else {
+			if (!vga_str_to_iostate
+			    (curr_pos, remaining, &io_state)) {
+				ret_val = -EPROTO;
+				goto done;
+			}
+			/* TODO: Add this?
+			   if (io_state == VGA_RSRC_NONE) {
+			   ret_val = -EPROTO;
+			   goto done;
+			   }
+			  */
+		}
+
+		pdev = priv->target;
+		if (priv->target == NULL) {
+				ret_val = -ENODEV;
+			goto done;
+		}
+
+		vga_put(pdev, io_state);
+		for (i = 0; i < MAX_USER_CARDS; i++) {
+			if (priv->cards[i].pdev == pdev) {
+				if (io_state & VGA_RSRC_LEGACY_IO)
+					priv->cards[i].io_cnt--;
+				if (io_state & VGA_RSRC_LEGACY_MEM)
+					priv->cards[i].mem_cnt--;
+				break;
+			}
+		}
+
+		ret_val = count;
+		goto done;
+	} else if (strncmp(curr_pos, "trylock ", 8) == 0) {
+		curr_pos += 8;
+		remaining -= 8;
+
+#ifdef DEBUG
+		printk(KERN_DEBUG "client 0x%X called 'trylock'\n", (int)priv);
+#endif
+		if (!vga_str_to_iostate(curr_pos, remaining, &io_state)) {
+			ret_val = -EPROTO;
+			goto done;
+		}
+		/* TODO: Add this?
+		   if (io_state == VGA_RSRC_NONE) {
+		   ret_val = -EPROTO;
+		   goto done;
+		   }
+		 */
+
+		pdev = priv->target;
+		if (priv->target == NULL) {
+			ret_val = -ENODEV;
+			goto done;
+		}
+
+		if (vga_tryget(pdev, io_state)) {
+			/* Update the client's locks lists... */
+			for (i = 0; i < MAX_USER_CARDS; i++) {
+				if (priv->cards[i].pdev == pdev) {
+					if (io_state & VGA_RSRC_LEGACY_IO)
+						priv->cards[i].io_cnt++;
+					if (io_state & VGA_RSRC_LEGACY_MEM)
+						priv->cards[i].mem_cnt++;
+					break;
+				}
+			}
+			ret_val = count;
+			goto done;
+		} else {
+			ret_val = -EBUSY;
+			goto done;
+		}
+
+	} else if (strncmp(curr_pos, "target ", 7) == 0) {
+		unsigned int domain, bus, devfn;
+		struct vga_device *vgadev;
+
+		curr_pos += 7;
+		remaining -= 7;
+#ifdef DEBUG
+		printk(KERN_DEBUG "client 0x%X called 'target'\n", (int)priv);
+#endif
+		if (!vga_pci_str_to_vars(curr_pos, remaining,
+					 &domain, &bus, &devfn)) {
+			ret_val = -EPROTO;
+			goto done;
+		}
+
+		pdev = pci_get_bus_and_slot(bus, devfn);
+		if (!pdev) {
+			printk(KERN_INFO "Invalid pci address!\n");
+			ret_val = -ENODEV;
+			goto done;
+		}
+
+		vgadev = vgadev_find(pdev);
+		if (vgadev == NULL) {
+			printk(KERN_INFO "This PCI is not a vga device\n");
+			ret_val = -ENODEV;
+			goto done;
+		}
+
+		priv->target = pdev;
+		for (i = 0; i < MAX_USER_CARDS; i++) {
+			if (priv->cards[i].pdev == pdev)
+				break;
+			if (priv->cards[i].pdev == NULL) {
+				priv->cards[i].pdev = pdev;
+				priv->cards[i].io_cnt = 0;
+				priv->cards[i].mem_cnt = 0;
+				break;
+			}
+		}
+		if (i == MAX_USER_CARDS) {
+			printk(KERN_ERR "Maximum user cards number reached!\n");
+			/* XXX: which value to return? */
+			ret_val =  -ENOMEM;
+			goto done;
+		}
+
+		ret_val = count;
+		goto done;
+
+
+	} else if (strncmp(curr_pos, "decodes ", 8) == 0) {
+		curr_pos += 8;
+		remaining -= 8;
+#ifdef DEBUG
+		printk(KERN_DEBUG "client 0x%X called 'decodes'\n", (int)priv);
+#endif
+
+		if (!vga_str_to_iostate(curr_pos, remaining, &io_state)) {
+			ret_val = -EPROTO;
+			goto done;
+		}
+		pdev = priv->target;
+		if (priv->target == NULL) {
+				ret_val = -ENODEV;
+			goto done;
+		}
+
+		vga_set_legacy_decoding(pdev, io_state);
+		ret_val = count;
+		goto done;
+	}
+	/* If we got here, the message written is not part of the protocol! */
+	kfree(kbuf);
+	return -EPROTO;
+
+done:
+	kfree(kbuf);
+	return ret_val;
+}
+
+static unsigned int vga_arb_fpoll(struct file *file, poll_table * wait)
+{
+	struct vga_arb_private *priv = file->private_data;
+
+#ifdef DEBUG
+	printk(KERN_DEBUG "vga_arb_fpoll()\n");
+#endif
+
+	if (priv == NULL)
+		return -ENODEV;
+	poll_wait(file, &vga_wait_queue, wait);
+	return POLLIN;
+}
+
+static int vga_arb_open(struct inode *inode, struct file *file)
+{
+	struct vga_arb_private *priv;
+	unsigned long flags;
+
+#ifdef DEBUG
+	printk(KERN_DEBUG "vga_arb_open()\n");
+#endif
+	priv = kmalloc(sizeof(struct vga_arb_private), GFP_KERNEL);
+	if (priv == NULL)
+		return -ENOMEM;
+	memset(priv, 0, sizeof(*priv));
+	spin_lock_init(&priv->lock);
+	file->private_data = priv;
+
+	spin_lock_irqsave(&vga_user_lock, flags);
+	list_add(&priv->list, &vga_user_list);
+	spin_unlock_irqrestore(&vga_user_lock, flags);
+
+	/* Set the client' lists of locks */
+	priv->target = vga_default_device(); /* Maybe this is still null! */
+	priv->cards[0].pdev = priv->target;
+	priv->cards[0].io_cnt = 0;
+	priv->cards[0].mem_cnt = 0;
+
+
+	return 0;
+}
+
+static int vga_arb_release(struct inode *inode, struct file *file)
+{
+	struct vga_arb_private *priv = file->private_data;
+	struct vga_arb_user_card *uc;
+	unsigned long flags;
+	int i;
+
+#ifdef DEBUG
+	printk(KERN_DEBUG "vga_arb_release()\n");
+#endif
+	if (priv == NULL)
+		return -ENODEV;
+
+	spin_lock_irqsave(&vga_user_lock, flags);
+	list_del(&priv->list);
+	for (i = 0; i < MAX_USER_CARDS; i++) {
+		uc = &priv->cards[i];
+		if (uc->pdev == NULL)
+			continue;
+#ifdef DEBUG
+		printk(KERN_DEBUG "uc->io_cnt == %d, uc->mem_cnt == %d\n",
+		       uc->io_cnt, uc->mem_cnt);
+#endif
+		while (uc->io_cnt--)
+			vga_put(uc->pdev, VGA_RSRC_LEGACY_IO);
+		while (uc->mem_cnt--)
+			vga_put(uc->pdev, VGA_RSRC_LEGACY_MEM);
+	}
+	spin_unlock_irqrestore(&vga_user_lock, flags);
+
+	kfree(priv);
+
+	return 0;
+}
+
+static void vga_arb_device_card_gone(struct pci_dev *pdev)
+{
+}
+
+static int pci_notify(struct notifier_block *nb, unsigned long action,
+		      void *data)
+{
+	struct device *dev = data;
+	struct pci_dev *pdev = to_pci_dev(dev);
+
+#ifdef DEBUG
+	printk(KERN_DEBUG "pci_notify()\n");
+#endif
+	/* For now we're only intereted in devices added and removed. I didn't
+	 * test this thing here, so someone needs to double check for the
+	 * cases of hotplugable vga cards. */
+	if (action == BUS_NOTIFY_ADD_DEVICE)
+		vga_arbiter_add_pci_device(pdev);
+	else if (action == BUS_NOTIFY_DEL_DEVICE)
+		vga_arbiter_del_pci_device(pdev);
+
+	return 0;
+}
+
+static struct notifier_block pci_notifier = {
+	.notifier_call = pci_notify,
+};
+
+static const struct file_operations vga_arb_device_fops = {
+	.read = vga_arb_read,
+	.write = vga_arb_write,
+	.poll = vga_arb_fpoll,
+	.open = vga_arb_open,
+	.release = vga_arb_release,
+};
+
+static struct miscdevice vga_arb_device = {
+	MISC_DYNAMIC_MINOR, "vga_arbiter", &vga_arb_device_fops
+};
+
+static int __init vga_arb_device_init(void)
+{
+	int rc;
+	struct pci_dev *pdev;
+
+	rc = misc_register(&vga_arb_device);
+	if (rc < 0)
+		printk(KERN_ERR
+		       "VGA Arbiter: error %d registering device\n", rc);
+
+	bus_register_notifier(&pci_bus_type, &pci_notifier);
+
+	/* We add all pci devices satisfying vga class in the arbiter by
+	 * default */
+	pdev = NULL;
+	while ((pdev =
+		pci_get_subsys(PCI_ANY_ID, PCI_ANY_ID, PCI_ANY_ID,
+			       PCI_ANY_ID, pdev)) != NULL)
+		vga_arbiter_add_pci_device(pdev);
+
+	printk(KERN_INFO "VGA Arbiter: loaded\n");
+	return rc;
+}
+
+static void __exit vga_arb_device_exit(void)
+{
+	misc_deregister(&vga_arb_device);
+#ifdef DEBUG
+	printk(KERN_DEBUG "VGA Arbiter: unloaded\n");
+#endif
+}
+
+MODULE_AUTHOR("Benjamin Herrenschmidt, Paulo R. Zanoni, Tiago Vignatti");
+MODULE_DESCRIPTION("VGA arbiter");
+MODULE_LICENSE("GPL");
+
+module_init(vga_arb_device_init);
+module_exit(vga_arb_device_exit);
diff --git a/drivers/gpu/vga/vgaarb.h b/drivers/gpu/vga/vgaarb.h
new file mode 100644
index 0000000..4dcff9e
--- /dev/null
+++ b/drivers/gpu/vga/vgaarb.h
@@ -0,0 +1,168 @@
+/*
+ * vgaarb.c
+ *
+ * (C) Copyright 2005 Benjamin Herrenschmidt <benh@kernel.crashing.org>
+ * (C) Copyright 2007 Paulo R. Zanoni <przanoni@gmail.com>
+ * (C) Copyright 2007, 2009 Tiago Vignatti <vignatti@freedesktop.org>
+ */
+
+#ifndef LINUX_VGA_H
+
+#include <asm/vga.h>
+
+/* Legacy VGA regions */
+#define VGA_RSRC_NONE	       0x00
+#define VGA_RSRC_LEGACY_IO     0x01
+#define VGA_RSRC_LEGACY_MEM    0x02
+#define VGA_RSRC_LEGACY_MASK   (VGA_RSRC_LEGACY_IO | VGA_RSRC_LEGACY_MEM)
+/* Non-legacy access */
+#define VGA_RSRC_NORMAL_IO     0x04
+#define VGA_RSRC_NORMAL_MEM    0x08
+
+/* Passing that instead of a pci_dev to use the system "default"
+ * device, that is the one used by vgacon. Archs will probably
+ * have to provide their own vga_default_device();
+ */
+#define VGA_DEFAULT_DEVICE     (NULL)
+
+/* For use by clients */
+
+/**
+ *     vga_set_legacy_decoding
+ *
+ *     @pdev: pci device of the VGA card
+ *     @decodes: bit mask of what legacy regions the card decodes
+ *
+ *     Indicates to the arbiter if the card decodes legacy VGA IOs,
+ *     legacy VGA Memory, both, or none. All cards default to both,
+ *     the card driver (fbdev for example) should tell the arbiter
+ *     if it has disabled legacy decoding, so the card can be left
+ *     out of the arbitration process (and can be safe to take
+ *     interrupts at any time.
+ */
+extern void vga_set_legacy_decoding(struct pci_dev *pdev,
+									unsigned int decodes);
+
+/**
+ *     vga_get         - acquire & locks VGA resources
+ *
+ *     pdev: pci device of the VGA card or NULL for the system default
+ *     rsrc: bit mask of resources to acquire and lock
+ *     interruptible: blocking should be interruptible by signals ?
+ *
+ *     This function acquires VGA resources for the given
+ *     card and mark those resources locked. If the resource requested
+ *     are "normal" (and not legacy) resources, the arbiter will first check
+ *     wether the card is doing legacy decoding for that type of resource. If
+ *     yes, the lock is "converted" into a legacy resource lock.
+ *     The arbiter will first look for all VGA cards that might conflict
+ *     and disable their IOs and/or Memory access, inlcuding VGA forwarding
+ *     on P2P bridges if necessary, so that the requested resources can
+ *     be used. Then, the card is marked as locking these resources and
+ *     the IO and/or Memory accesse are enabled on the card (including
+ *     VGA forwarding on parent P2P bridges if any).
+ *     This function will block if some conflicting card is already locking
+ *     one of the required resources (or any resource on a different bus
+ *     segment, since P2P bridges don't differenciate VGA memory and IO
+ *     afaik). You can indicate wether this blocking should be interruptible
+ *     by a signal (for userland interface) or not.
+ *     Must not be called at interrupt time or in atomic context.
+ *     If the card already owns the resources, the function succeeds.
+ *     Nested calls are supported (a per-resource counter is maintained)
+ */
+
+extern int vga_get(struct pci_dev *pdev, unsigned int rsrc,
+											int interruptible);
+
+/**
+ *     vga_get_interruptible
+ *
+ *     Shortcut to vga_get
+ */
+
+static inline int vga_get_interruptible(struct pci_dev *pdev,
+										unsigned int rsrc)
+{
+       return vga_get(pdev, rsrc, 1);
+}
+
+/**
+ *     vga_get_interruptible
+ *
+ *     Shortcut to vga_get
+ */
+
+static inline int vga_get_uninterruptible(struct pci_dev *pdev,
+											unsigned int rsrc)
+{
+       return vga_get(pdev, rsrc, 0);
+}
+
+/**
+ *     vga_tryget      - try to acquire & lock legacy VGA resources
+ *
+ *     @pdev: pci devivce of VGA card or NULL for system default
+ *     @rsrc: bit mask of resources to acquire and lock
+ *
+ *     This function performs the same operation as vga_get(), but
+ *     will return an error (-EBUSY) instead of blocking if the resources
+ *     are already locked by another card. It can be called in any context
+ */
+
+extern int vga_tryget(struct pci_dev *pdev, unsigned int rsrc);
+
+/**
+ *     vga_put         - release lock on legacy VGA resources
+ *
+ *     @pdev: pci device of VGA card or NULL for system default
+ *     @rsrc: but mask of resource to release
+ *
+ *     This function releases resources previously locked by vga_get()
+ *     or vga_tryget(). The resources aren't disabled right away, so
+ *     that a subsequence vga_get() on the same card will succeed
+ *     immediately. Resources have a counter, so locks are only
+ *     released if the counter reaches 0.
+ */
+
+extern void vga_put(struct pci_dev *pdev, unsigned int rsrc);
+
+
+/**
+ *     vga_default_device
+ *
+ *     This can be defined by the platform. The default implementation
+ *     is rather dumb and will probably only work properly on single
+ *     vga card setups and/or x86 platforms.
+ *
+ *     If your VGA default device is not PCI, you'll have to return
+ *     NULL here. In this case, I assume it will not conflict with
+ *     any PCI card. If this is not true, I'll have to define two archs
+ *     hooks for enabling/disabling the VGA default device if that is
+ *     possible. This may be a problem with real _ISA_ VGA cards, in
+ *     addition to a PCI one. I don't know at this point how to deal
+ *     with that card. Can theirs IOs be disabled at all ? If not, then
+ *     I suppose it's a matter of having the proper arch hook telling
+ *     us about it, so we basically never allow anybody to succeed a
+ *     vga_get()...
+ */
+
+#ifndef __ARCH_HAS_VGA_DEFAULT_DEVICE
+extern struct pci_dev *vga_default_device(void);
+#endif
+
+/**
+ *     vga_conflicts
+ *
+ *     Architectures should define this if they have several
+ *     independant PCI domains that can afford concurrent VGA
+ *     decoding
+ */
+
+#ifndef __ARCH_HAS_VGA_CONFLICT
+static inline int vga_conflicts(struct pci_dev *p1, struct pci_dev *p2)
+{
+       return 1;
+}
+#endif
+
+#endif /* LINUX_VGA_H */
diff --git a/drivers/video/Kconfig b/drivers/video/Kconfig
index 8afcf08..f4ed145 100644
--- a/drivers/video/Kconfig
+++ b/drivers/video/Kconfig
@@ -7,6 +7,8 @@ menu "Graphics support"
 
 source "drivers/char/agp/Kconfig"
 
+source "drivers/gpu/vga/Kconfig"
+
 source "drivers/gpu/drm/Kconfig"
 
 config VGASTATE
-- 
1.5.6.3