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SubjectRe: [PATCH] vga: implements VGA arbitration on Linux
Hi,

some minor comments below.

On Tue, 11 Aug 2009 15:52:06 +1000
Dave Airlie <airlied@gmail.com> wrote:

> From: Tiago Vignatti <tiago.vignatti@nokia.com>
>
> Background:
> Graphic devices are accessed through ranges in I/O or memory space. While most
> modern devices allow relocation of such ranges, some "Legacy" VGA devices
> implemented on PCI will typically have the same "hard-decoded" addresses as
> they did on ISA. For more details see "PCI Bus Binding to IEEE Std 1275-1994
> Standard for Boot (Initialization Configuration) Firmware Revision 2.1"
> Section 7, Legacy Devices.
>
> The Resource Access Control (RAC) module inside the X server currently does
> the task of arbitration when more than one legacy device co-exists on the same
> machine. But the problem happens when these devices are trying to be accessed
> by different userspace clients (e.g. two server in parallel). Their address
> assignments conflict. Therefore an arbitration scheme _outside_ of the X
> server is needed to control the sharing of these resources. This document
> introduces the operation of the VGA arbiter implemented for Linux kernel.
>
> Signed-off-by: Tiago Vignatti <tiago.vignatti@nokia.com>
> Signed-off-by: Dave Airlie <airlied@redhat.com>
> ---
> drivers/gpu/Makefile | 2 +-
> drivers/gpu/vga/Kconfig | 10 +
> drivers/gpu/vga/Makefile | 1 +
> drivers/gpu/vga/vgaarb.c | 1206 ++++++++++++++++++++++++++++++++++++++++++++++
> drivers/pci/pci.c | 44 ++
> drivers/video/Kconfig | 2 +
> include/linux/pci.h | 2 +
> include/linux/vgaarb.h | 195 ++++++++
> 8 files changed, 1461 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 include/linux/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..790e675
> --- /dev/null
> +++ b/drivers/gpu/vga/Kconfig
> @@ -0,0 +1,10 @@
> +config VGA_ARB
> + bool "VGA Arbitration" if EMBEDDED
> + default y
> + depends on PCI
> + 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.

The file Documentation/vgaarbiter.txt does not exist.

> 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..199138f
> --- /dev/null
> +++ b/drivers/gpu/vga/vgaarb.c
> @@ -0,0 +1,1206 @@
> +/*
> + * 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

Another reference to 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 <linux/vgaarb.h>
> +
> +static void vga_arbiter_notify_clients(void);
> +/*
> + * 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 */
> +
> + /* allow IRQ enable/disable hook */
> + void *cookie;
> + void (*irq_set_state)(void *cookie, bool enable);
> + unsigned int (*set_vga_decode)(void *cookie, bool decode);
> +};
> +
> +static LIST_HEAD(vga_list);
> +static int vga_count, vga_decode_count;
> +static bool vga_arbiter_used;
> +static DEFINE_SPINLOCK(vga_lock);
> +static DECLARE_WAIT_QUEUE_HEAD(vga_wait_queue);
> +
> +
> +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)
> +{
> + /* we could in theory hand out locks on IO and mem
> + * separately to userspace but it can cause deadlocks */
> + if (strncmp(buf, "none", 4) == 0) {
> + *io_state = VGA_RSRC_NONE;
> + return 1;
> + }
> +
> + /* XXX We're not chekcing the str_size! */
> + if (strncmp(buf, "io+mem", 6) == 0)
> + goto both;
> + else if (strncmp(buf, "io", 2) == 0)
> + goto both;
> + else if (strncmp(buf, "mem", 3) == 0)
> + goto both;
> + return 0;
> +both:
> + *io_state = VGA_RSRC_LEGACY_IO | VGA_RSRC_LEGACY_MEM;
> + return 1;
> +}
> +
> +#ifndef __ARCH_HAS_VGA_DEFAULT_DEVICE
> +/* this is only used a cookie - it should not be dereferenced */
> +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
> +
> +static inline void vga_irq_set_state(struct vga_device *vgadev, bool state)
> +{
> + if (vgadev->irq_set_state)
> + vgadev->irq_set_state(vgadev->cookie, state);
> +}
> +
> +
> +/* If we don't ever use VGA arb we should avoid
> + turning off anything anywhere due to old X servers getting
> + confused about the boot device not being VGA */
> +static void vga_check_first_use(void)
> +{
> + /* we should inform all GPUs in the system that
> + * VGA arb has occured and to try and disable resources
> + * if they can */
> + if (!vga_arbiter_used) {
> + vga_arbiter_used = true;
> + vga_arbiter_notify_clients();
> + }
> +}
> +
> +static struct vga_device *__vga_tryget(struct vga_device *vgadev,
> + unsigned int rsrc)
> +{
> + unsigned int wants, legacy_wants, match;
> + struct vga_device *conflict;
> + unsigned int pci_bits;
> + /* 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;
> +
> + pr_devel("%s: %d\n", __func__, rsrc);
> + pr_devel("%s: owns: %d\n", __func__, vgadev->owns);
> +
> + /* 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
> + */

Does this comment mean "We don't need to request a legacy resource,
therefore ..." or "If a legacy resource is not required, ..."?
Well, it gets clear when I read and think about the code, but
the comment got me confused for a moment.

> + 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 */

We don't what?

> + 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_irq_set_state(conflict, false);
> +
> + pci_bits = 0;
> + if (lwants & (VGA_RSRC_LEGACY_MEM|VGA_RSRC_NORMAL_MEM))
> + pci_bits |= PCI_COMMAND_MEMORY;
> + if (lwants & (VGA_RSRC_LEGACY_IO|VGA_RSRC_NORMAL_IO))
> + pci_bits |= PCI_COMMAND_IO;
> +
> + pci_set_vga_state(conflict->pdev, false, pci_bits,
> + 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.
> + */
> + pci_bits = 0;
> + if (wants & (VGA_RSRC_LEGACY_MEM|VGA_RSRC_NORMAL_MEM))
> + pci_bits |= PCI_COMMAND_MEMORY;
> + if (wants & (VGA_RSRC_LEGACY_IO|VGA_RSRC_NORMAL_IO))
> + pci_bits |= PCI_COMMAND_IO;
> + pci_set_vga_state(vgadev->pdev, true, pci_bits, !!(wants & VGA_RSRC_LEGACY_MASK));
> +
> + vga_irq_set_state(vgadev, true);
> + 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;
> +
> + pr_devel("%s\n", __func__);
> +
> + /* 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;
> +
> + vga_check_first_use();
> + /* 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;
> +}
> +EXPORT_SYMBOL(vga_get);
> +
> +int vga_tryget(struct pci_dev *pdev, unsigned int rsrc)
> +{
> + struct vga_device *vgadev;
> + unsigned long flags;
> + int rc = 0;
> +
> + vga_check_first_use();
> +
> + /* 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;
> +}
> +EXPORT_SYMBOL(vga_tryget);
> +
> +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);
> +}
> +EXPORT_SYMBOL(vga_put);
> +
> +/*
> + * 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 bool 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 false;
> +
> + /* Allocate structure */
> + vgadev = kmalloc(sizeof(struct vga_device), GFP_KERNEL);
> + if (vgadev == NULL) {
> + pr_err("vgaarb: failed to allocate pci device\n");
> + /* 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 false;
> + }
> +
> + 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;
> +
> + /* by default mark it as decoding */
> + vga_decode_count++;
> + /* 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_MASK) == VGA_RSRC_LEGACY_MASK))
> + vga_default = pci_dev_get(pdev);
> +#endif
> +
> + /* Add to the list */
> + list_add(&vgadev->list, &vga_list);
> + vga_count++;
> + pr_info("vgaarb: device added: PCI:%s,decodes=%s,owns=%s,locks=%s\n",
> + pci_name(pdev),
> + vga_iostate_to_str(vgadev->decodes),
> + vga_iostate_to_str(vgadev->owns),
> + vga_iostate_to_str(vgadev->locks));
> +
> + spin_unlock_irqrestore(&vga_lock, flags);
> + return true;
> +fail:
> + spin_unlock_irqrestore(&vga_lock, flags);
> + kfree(vgadev);
> + return false;
> +}
> +
> +static bool vga_arbiter_del_pci_device(struct pci_dev *pdev)
> +{
> + struct vga_device *vgadev;
> + unsigned long flags;
> + bool ret = true;
> +
> + spin_lock_irqsave(&vga_lock, flags);
> + vgadev = vgadev_find(pdev);
> + if (vgadev == NULL) {
> + ret = false;
> + goto bail;
> + }
> +
> + if (vga_default == pdev) {
> + pci_dev_put(vga_default);
> + vga_default = NULL;
> + }
> +
> + if (vgadev->decodes & (VGA_RSRC_LEGACY_IO | VGA_RSRC_LEGACY_MEM))
> + vga_decode_count--;
> +
> + /* Remove entry from list */
> + list_del(&vgadev->list);
> + vga_count--;
> + /* 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);
> + return ret;
> +}
> +
> +/* this is called with the lock */
> +static inline void vga_update_device_decodes(struct vga_device *vgadev,
> + int new_decodes)
> +{
> + int old_decodes;
> + struct vga_device *new_vgadev, *conflict;
> +
> + old_decodes = vgadev->decodes;
> + vgadev->decodes = new_decodes;
> +
> + pr_info("vgaarb: device changed decodes: PCI:%s,olddecodes=%s,decodes=%s:owns=%s\n",
> + pci_name(vgadev->pdev),
> + vga_iostate_to_str(old_decodes),
> + vga_iostate_to_str(vgadev->decodes),
> + vga_iostate_to_str(vgadev->owns));
> +
> +
> + /* if we own the decodes we should move them along to
> + another card */
> + if ((vgadev->owns & old_decodes) && (vga_count > 1)) {
> + /* set us to own nothing */
> + vgadev->owns &= ~old_decodes;
> + list_for_each_entry(new_vgadev, &vga_list, list) {
> + if ((new_vgadev != vgadev) &&
> + (new_vgadev->decodes & VGA_RSRC_LEGACY_MASK)) {
> + pr_info("vgaarb: transferring owner from PCI:%s to PCI:%s\n", pci_name(vgadev->pdev), pci_name(new_vgadev->pdev));
> + conflict = __vga_tryget(new_vgadev, VGA_RSRC_LEGACY_MASK);
> + if (!conflict)
> + __vga_put(new_vgadev, VGA_RSRC_LEGACY_MASK);
> + break;
> + }
> + }
> + }
> +
> + /* change decodes counter */
> + if (old_decodes != new_decodes) {
> + if (new_decodes & (VGA_RSRC_LEGACY_IO | VGA_RSRC_LEGACY_MEM))
> + vga_decode_count++;
> + else
> + vga_decode_count--;
> + }
> +}
> +
> +void __vga_set_legacy_decoding(struct pci_dev *pdev, unsigned int decodes, bool userspace)
> +{
> + 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;
> +
> + /* don't let userspace futz with kernel driver decodes */
> + if (userspace && vgadev->set_vga_decode)
> + goto bail;
> +
> + /* update the device decodes + counter */
> + vga_update_device_decodes(vgadev, 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);
> +}
> +
> +void vga_set_legacy_decoding(struct pci_dev *pdev, unsigned int decodes)
> +{
> + __vga_set_legacy_decoding(pdev, decodes, false);
> +}
> +EXPORT_SYMBOL(vga_set_legacy_decoding);
> +
> +/* return number of active VGA devices */

That comment is incorrect.

> +/* call with NULL to unregister */
> +int vga_client_register(struct pci_dev *pdev, void *cookie,
> + void (*irq_set_state)(void *cookie, bool state),
> + unsigned int (*set_vga_decode)(void *cookie, bool decode))
> +{
> + int ret = -1;
> + struct vga_device *vgadev;
> + unsigned long flags;
> +
> + spin_lock_irqsave(&vga_lock, flags);
> + vgadev = vgadev_find(pdev);
> + if (!vgadev)
> + goto bail;
> +
> + vgadev->irq_set_state = irq_set_state;
> + vgadev->set_vga_decode = set_vga_decode;
> + vgadev->cookie = cookie;
> + ret = 0;
> +
> +bail:
> + spin_unlock_irqrestore(&vga_lock, flags);
> + return ret;
> +
> +}
> +EXPORT_SYMBOL(vga_client_register);
> +
> +/*
> + * 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);
> +
> +
> +/*
> + * 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:%x:%x:%x.%x", 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;
> +
> + 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,
> + "count:%d,PCI:%s,decodes=%s,owns=%s,locks=%s(%d:%d)\n",
> + vga_decode_count, 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 vga_arb_user_card *uc = NULL;
> + 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;
> +
> + pr_devel("client 0x%X called 'lock'\n", (int)priv);
> +
> + 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;
> +
> + pr_devel("client 0x%X called 'unlock'\n", (int)priv);
> +
> + 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;
> + }
> + for (i = 0; i < MAX_USER_CARDS; i++) {
> + if (priv->cards[i].pdev == pdev)
> + uc = &priv->cards[i];
> + }
> +
> + if (!uc)
> + return -EINVAL;
> +
> + if (io_state & VGA_RSRC_LEGACY_IO && uc->io_cnt == 0)
> + return -EINVAL;
> +
> + if (io_state & VGA_RSRC_LEGACY_MEM && uc->mem_cnt == 0)
> + return -EINVAL;
> +
> + vga_put(pdev, io_state);
> +
> + if (io_state & VGA_RSRC_LEGACY_IO)
> + uc->io_cnt--;
> + if (io_state & VGA_RSRC_LEGACY_MEM)
> + uc->mem_cnt--;
> +
> + ret_val = count;
> + goto done;
> + } else if (strncmp(curr_pos, "trylock ", 8) == 0) {
> + curr_pos += 8;
> + remaining -= 8;
> +
> + pr_devel("client 0x%X called 'trylock'\n", (int)priv);
> +
> + 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;
> + pr_devel("client 0x%X called 'target'\n", (int)priv);
> + /* if target is default */
> + if (!strncmp(buf, "default", 7))
> + pdev = pci_dev_get(vga_default_device());
> + else {
> + 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) {
> + pr_info("vgaarb: invalid PCI address!\n");
> + ret_val = -ENODEV;
> + goto done;
> + }
> + }
> +
> + vgadev = vgadev_find(pdev);
> + if (vgadev == NULL) {
> + pr_info("vgaarb: this pci device is not a vga device\n");
> + pci_dev_put(pdev);
> + 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) {
> + pr_err("vgaarb: maximum user cards number reached!\n");
> + pci_dev_put(pdev);
> + /* XXX: which value to return? */
> + ret_val = -ENOMEM;
> + goto done;
> + }
> +
> + ret_val = count;
> + pci_dev_put(pdev);
> + goto done;
> +
> +
> + } else if (strncmp(curr_pos, "decodes ", 8) == 0) {
> + curr_pos += 8;
> + remaining -= 8;
> + pr_devel("vgaarb: client 0x%X called 'decodes'\n", (int)priv);
> +
> + 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, true);
> + 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;
> +}

How about splitting those else-if case implementations into separate
functions?

> +
> +static unsigned int vga_arb_fpoll(struct file *file, poll_table * wait)
> +{
> + struct vga_arb_private *priv = file->private_data;
> +
> + pr_devel("%s\n", __func__);
> +
> + 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;
> +
> + pr_devel("%s\n", __func__);
> +
> + 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;
> +
> + pr_devel("%s\n", __func__);
> +
> + 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;
> + pr_devel("uc->io_cnt == %d, uc->mem_cnt == %d\n",
> + uc->io_cnt, uc->mem_cnt);
> + 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)
> +{
> +}
> +
> +/*
> + * callback any registered clients to let them know we have a
> + * change in VGA cards
> + */
> +static void vga_arbiter_notify_clients(void)
> +{
> + struct vga_device *vgadev;
> + unsigned long flags;
> + uint32_t new_decodes;
> + bool new_state;
> +
> + if (!vga_arbiter_used)
> + return;
> +
> + spin_lock_irqsave(&vga_lock, flags);
> + list_for_each_entry(vgadev, &vga_list, list) {
> + if (vga_count > 1)
> + new_state = false;
> + else
> + new_state = true;
> + if (vgadev->set_vga_decode) {
> + new_decodes = vgadev->set_vga_decode(vgadev->cookie, new_state);
> + vga_update_device_decodes(vgadev, new_decodes);
> + }
> + }
> + spin_unlock_irqrestore(&vga_lock, flags);
> +}
> +
> +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);
> + bool notify = false;
> +
> + pr_devel("%s\n", __func__);
> +
> + /* 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)
> + notify = vga_arbiter_add_pci_device(pdev);
> + else if (action == BUS_NOTIFY_DEL_DEVICE)
> + notify = vga_arbiter_del_pci_device(pdev);
> +
> + if (notify)
> + vga_arbiter_notify_clients();
> + 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)
> + pr_err("vgaarb: 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);
> +
> + pr_info("vgaarb: loaded\n");
> + return rc;
> +}
> +subsys_initcall(vga_arb_device_init);
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index dbd0f94..d837606 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -2502,6 +2502,50 @@ int pci_resource_bar(struct pci_dev *dev, int resno, enum pci_bar_type *type)
> return 0;
> }
>
> +/**
> + * pci_set_vga_state - set VGA decode state on device and parents if requested
> + * @dev the PCI device
> + * @decode - true = enable decoding, false = disable decoding
> + * @command_bits PCI_COMMAND_IO and/or PCI_COMMAND_MEMORY
> + * @change_bridge - traverse ancestors and change bridges
> + */
> +int pci_set_vga_state(struct pci_dev *dev, bool decode,
> + unsigned int command_bits, bool change_bridge)
> +{
> + struct pci_bus *bus;
> + struct pci_dev *bridge;
> + u16 cmd;
> +
> + WARN_ON(command_bits & ~(PCI_COMMAND_IO|PCI_COMMAND_MEMORY));
> +
> + pci_read_config_word(dev, PCI_COMMAND, &cmd);
> + if (decode == true)
> + cmd |= command_bits;
> + else
> + cmd &= ~command_bits;
> + pci_write_config_word(dev, PCI_COMMAND, cmd);
> +
> + if (change_bridge == false)
> + return 0;
> +
> + bus = dev->bus;
> + while (bus) {
> + bridge = bus->self;
> + if (bridge) {
> + pci_read_config_word(bridge, PCI_BRIDGE_CONTROL,
> + &cmd);
> + if (decode == true)
> + cmd |= PCI_BRIDGE_CTL_VGA;
> + else
> + cmd &= ~PCI_BRIDGE_CTL_VGA;
> + pci_write_config_word(bridge, PCI_BRIDGE_CONTROL,
> + cmd);
> + }
> + bus = bus->parent;
> + }
> + return 0;
> +}
> +
> #define RESOURCE_ALIGNMENT_PARAM_SIZE COMMAND_LINE_SIZE
> static char resource_alignment_param[RESOURCE_ALIGNMENT_PARAM_SIZE] = {0};
> spinlock_t resource_alignment_lock = SPIN_LOCK_UNLOCKED;
> diff --git a/drivers/video/Kconfig b/drivers/video/Kconfig
> index 3b54b39..a0d9ee1 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
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 115fb7b..7ba6eba 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -805,6 +805,8 @@ int pci_cfg_space_size_ext(struct pci_dev *dev);
> int pci_cfg_space_size(struct pci_dev *dev);
> unsigned char pci_bus_max_busnr(struct pci_bus *bus);
>
> +int pci_set_vga_state(struct pci_dev *pdev, bool decode,
> + unsigned int command_bits, bool change_bridge);
> /* kmem_cache style wrapper around pci_alloc_consistent() */
>
> #include <linux/dmapool.h>
> diff --git a/include/linux/vgaarb.h b/include/linux/vgaarb.h
> new file mode 100644
> index 0000000..68229ce
> --- /dev/null
> +++ b/include/linux/vgaarb.h
> @@ -0,0 +1,195 @@
> +/*
> + * 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 ?

I don't know the kerneldoc format, but looks like argument names
should be prefixed with @.

> + *
> + * 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

Should be vga_get_uninterruptible.

> + *
> + * 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
> +
> +/*
> + * Register a client with the VGA arbitration logic
> + * return value: number of VGA devices in system.

The return value is documented incorrectly here.

> + *
> + * Clients have two callback mechanisms they can use.
> + * irq enable/disable callback -
> + * If a client can't disable its GPUs VGA resources, then we
> + * need to be able to ask it to turn off its irqs when we
> + * turn off its mem and io decoding.
> + * set_vga_decode
> + * If a client can disable its GPU VGA resource, it will
> + * get a callback from this to set the encode/decode state
> + *
> + * Clients with disable abilities should check the return value
> + * of this function and if the VGA device count is > 1, should
> + * disable VGA decoding resources.
> + *
> + * Rationale: we cannot disable VGA decode resources unconditionally
> + * some single GPU laptops seem to require ACPI or BIOS access to the
> + * VGA registers to control things like backlights etc.
> + * Hopefully newer multi-GPU laptops do something saner, and desktops
> + * won't have any special ACPI for this.
> + */
> +int vga_client_register(struct pci_dev *pdev, void *cookie,
> + void (*irq_set_state)(void *cookie, bool state),
> + unsigned int (*set_vga_decode)(void *cookie, bool state));
> +
> +#endif /* LINUX_VGA_H */
> --
> 1.6.0.6

--
Pekka Paalanen
http://www.iki.fi/pq/



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