PowerPC: adapt for dma_map_ops changes

[deliverable/linux.git] / arch / powerpc / kernel / vio.c

/*
 * IBM PowerPC Virtual I/O Infrastructure Support.
 *
 *    Copyright (c) 2003,2008 IBM Corp.
 *     Dave Engebretsen engebret@us.ibm.com
 *     Santiago Leon santil@us.ibm.com
 *     Hollis Blanchard <hollisb@us.ibm.com>
 *     Stephen Rothwell
 *     Robert Jennings <rcjenn@us.ibm.com>
 *
 *      This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 */

#include <linux/types.h>
#include <linux/stat.h>
#include <linux/device.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/console.h>
#include <linux/export.h>
#include <linux/mm.h>
#include <linux/dma-mapping.h>
#include <linux/kobject.h>

#include <asm/iommu.h>
#include <asm/dma.h>
#include <asm/vio.h>
#include <asm/prom.h>
#include <asm/firmware.h>
#include <asm/tce.h>
#include <asm/abs_addr.h>
#include <asm/page.h>
#include <asm/hvcall.h>
#include <asm/iseries/vio.h>
#include <asm/iseries/hv_types.h>
#include <asm/iseries/hv_lp_config.h>
#include <asm/iseries/hv_call_xm.h>
#include <asm/iseries/iommu.h>

static struct bus_type vio_bus_type;

static struct vio_dev vio_bus_device  = { /* fake "parent" device */
        .name = "vio",
        .type = "",
        .dev.init_name = "vio",
        .dev.bus = &vio_bus_type,
};

#ifdef CONFIG_PPC_SMLPAR
/**
 * vio_cmo_pool - A pool of IO memory for CMO use
 *
 * @size: The size of the pool in bytes
 * @free: The amount of free memory in the pool
 */
struct vio_cmo_pool {
        size_t size;
        size_t free;
};

/* How many ms to delay queued balance work */
#define VIO_CMO_BALANCE_DELAY 100

/* Portion out IO memory to CMO devices by this chunk size */
#define VIO_CMO_BALANCE_CHUNK 131072

/**
 * vio_cmo_dev_entry - A device that is CMO-enabled and requires entitlement
 *
 * @vio_dev: struct vio_dev pointer
 * @list: pointer to other devices on bus that are being tracked
 */
struct vio_cmo_dev_entry {
        struct vio_dev *viodev;
        struct list_head list;
};

/**
 * vio_cmo - VIO bus accounting structure for CMO entitlement
 *
 * @lock: spinlock for entire structure
 * @balance_q: work queue for balancing system entitlement
 * @device_list: list of CMO-enabled devices requiring entitlement
 * @entitled: total system entitlement in bytes
 * @reserve: pool of memory from which devices reserve entitlement, incl. spare
 * @excess: pool of excess entitlement not needed for device reserves or spare
 * @spare: IO memory for device hotplug functionality
 * @min: minimum necessary for system operation
 * @desired: desired memory for system operation
 * @curr: bytes currently allocated
 * @high: high water mark for IO data usage
 */
struct vio_cmo {
        spinlock_t lock;
        struct delayed_work balance_q;
        struct list_head device_list;
        size_t entitled;
        struct vio_cmo_pool reserve;
        struct vio_cmo_pool excess;
        size_t spare;
        size_t min;
        size_t desired;
        size_t curr;
        size_t high;
} vio_cmo;

/**
 * vio_cmo_OF_devices - Count the number of OF devices that have DMA windows
 */
static int vio_cmo_num_OF_devs(void)
{
        struct device_node *node_vroot;
        int count = 0;

        /*
         * Count the number of vdevice entries with an
         * ibm,my-dma-window OF property
         */
        node_vroot = of_find_node_by_name(NULL, "vdevice");
        if (node_vroot) {
                struct device_node *of_node;
                struct property *prop;

                for_each_child_of_node(node_vroot, of_node) {
                        prop = of_find_property(of_node, "ibm,my-dma-window",
                                               NULL);
                        if (prop)
                                count++;
                }
        }
        of_node_put(node_vroot);
        return count;
}

/**
 * vio_cmo_alloc - allocate IO memory for CMO-enable devices
 *
 * @viodev: VIO device requesting IO memory
 * @size: size of allocation requested
 *
 * Allocations come from memory reserved for the devices and any excess
 * IO memory available to all devices.  The spare pool used to service
 * hotplug must be equal to %VIO_CMO_MIN_ENT for the excess pool to be
 * made available.
 *
 * Return codes:
 *  0 for successful allocation and -ENOMEM for a failure
 */
static inline int vio_cmo_alloc(struct vio_dev *viodev, size_t size)
{
        unsigned long flags;
        size_t reserve_free = 0;
        size_t excess_free = 0;
        int ret = -ENOMEM;

        spin_lock_irqsave(&vio_cmo.lock, flags);

        /* Determine the amount of free entitlement available in reserve */
        if (viodev->cmo.entitled > viodev->cmo.allocated)
                reserve_free = viodev->cmo.entitled - viodev->cmo.allocated;

        /* If spare is not fulfilled, the excess pool can not be used. */
        if (vio_cmo.spare >= VIO_CMO_MIN_ENT)
                excess_free = vio_cmo.excess.free;

        /* The request can be satisfied */
        if ((reserve_free + excess_free) >= size) {
                vio_cmo.curr += size;
                if (vio_cmo.curr > vio_cmo.high)
                        vio_cmo.high = vio_cmo.curr;
                viodev->cmo.allocated += size;
                size -= min(reserve_free, size);
                vio_cmo.excess.free -= size;
                ret = 0;
        }

        spin_unlock_irqrestore(&vio_cmo.lock, flags);
        return ret;
}

/**
 * vio_cmo_dealloc - deallocate IO memory from CMO-enable devices
 * @viodev: VIO device freeing IO memory
 * @size: size of deallocation
 *
 * IO memory is freed by the device back to the correct memory pools.
 * The spare pool is replenished first from either memory pool, then
 * the reserve pool is used to reduce device entitlement, the excess
 * pool is used to increase the reserve pool toward the desired entitlement
 * target, and then the remaining memory is returned to the pools.
 *
 */
static inline void vio_cmo_dealloc(struct vio_dev *viodev, size_t size)
{
        unsigned long flags;
        size_t spare_needed = 0;
        size_t excess_freed = 0;
        size_t reserve_freed = size;
        size_t tmp;
        int balance = 0;

        spin_lock_irqsave(&vio_cmo.lock, flags);
        vio_cmo.curr -= size;

        /* Amount of memory freed from the excess pool */
        if (viodev->cmo.allocated > viodev->cmo.entitled) {
                excess_freed = min(reserve_freed, (viodev->cmo.allocated -
                                                   viodev->cmo.entitled));
                reserve_freed -= excess_freed;
        }

        /* Remove allocation from device */
        viodev->cmo.allocated -= (reserve_freed + excess_freed);

        /* Spare is a subset of the reserve pool, replenish it first. */
        spare_needed = VIO_CMO_MIN_ENT - vio_cmo.spare;

        /*
         * Replenish the spare in the reserve pool from the excess pool.
         * This moves entitlement into the reserve pool.
         */
        if (spare_needed && excess_freed) {
                tmp = min(excess_freed, spare_needed);
                vio_cmo.excess.size -= tmp;
                vio_cmo.reserve.size += tmp;
                vio_cmo.spare += tmp;
                excess_freed -= tmp;
                spare_needed -= tmp;
                balance = 1;
        }

        /*
         * Replenish the spare in the reserve pool from the reserve pool.
         * This removes entitlement from the device down to VIO_CMO_MIN_ENT,
         * if needed, and gives it to the spare pool. The amount of used
         * memory in this pool does not change.
         */
        if (spare_needed && reserve_freed) {
                tmp = min3(spare_needed, reserve_freed, (viodev->cmo.entitled - VIO_CMO_MIN_ENT));

                vio_cmo.spare += tmp;
                viodev->cmo.entitled -= tmp;
                reserve_freed -= tmp;
                spare_needed -= tmp;
                balance = 1;
        }

        /*
         * Increase the reserve pool until the desired allocation is met.
         * Move an allocation freed from the excess pool into the reserve
         * pool and schedule a balance operation.
         */
        if (excess_freed && (vio_cmo.desired > vio_cmo.reserve.size)) {
                tmp = min(excess_freed, (vio_cmo.desired - vio_cmo.reserve.size));

                vio_cmo.excess.size -= tmp;
                vio_cmo.reserve.size += tmp;
                excess_freed -= tmp;
                balance = 1;
        }

        /* Return memory from the excess pool to that pool */
        if (excess_freed)
                vio_cmo.excess.free += excess_freed;

        if (balance)
                schedule_delayed_work(&vio_cmo.balance_q, VIO_CMO_BALANCE_DELAY);
        spin_unlock_irqrestore(&vio_cmo.lock, flags);
}

/**
 * vio_cmo_entitlement_update - Manage system entitlement changes
 *
 * @new_entitlement: new system entitlement to attempt to accommodate
 *
 * Increases in entitlement will be used to fulfill the spare entitlement
 * and the rest is given to the excess pool.  Decreases, if they are
 * possible, come from the excess pool and from unused device entitlement
 *
 * Returns: 0 on success, -ENOMEM when change can not be made
 */
int vio_cmo_entitlement_update(size_t new_entitlement)
{
        struct vio_dev *viodev;
        struct vio_cmo_dev_entry *dev_ent;
        unsigned long flags;
        size_t avail, delta, tmp;

        spin_lock_irqsave(&vio_cmo.lock, flags);

        /* Entitlement increases */
        if (new_entitlement > vio_cmo.entitled) {
                delta = new_entitlement - vio_cmo.entitled;

                /* Fulfill spare allocation */
                if (vio_cmo.spare < VIO_CMO_MIN_ENT) {
                        tmp = min(delta, (VIO_CMO_MIN_ENT - vio_cmo.spare));
                        vio_cmo.spare += tmp;
                        vio_cmo.reserve.size += tmp;
                        delta -= tmp;
                }

                /* Remaining new allocation goes to the excess pool */
                vio_cmo.entitled += delta;
                vio_cmo.excess.size += delta;
                vio_cmo.excess.free += delta;

                goto out;
        }

        /* Entitlement decreases */
        delta = vio_cmo.entitled - new_entitlement;
        avail = vio_cmo.excess.free;

        /*
         * Need to check how much unused entitlement each device can
         * sacrifice to fulfill entitlement change.
         */
        list_for_each_entry(dev_ent, &vio_cmo.device_list, list) {
                if (avail >= delta)
                        break;

                viodev = dev_ent->viodev;
                if ((viodev->cmo.entitled > viodev->cmo.allocated) &&
                    (viodev->cmo.entitled > VIO_CMO_MIN_ENT))
                                avail += viodev->cmo.entitled -
                                         max_t(size_t, viodev->cmo.allocated,
                                               VIO_CMO_MIN_ENT);
        }

        if (delta <= avail) {
                vio_cmo.entitled -= delta;

                /* Take entitlement from the excess pool first */
                tmp = min(vio_cmo.excess.free, delta);
                vio_cmo.excess.size -= tmp;
                vio_cmo.excess.free -= tmp;
                delta -= tmp;

                /*
                 * Remove all but VIO_CMO_MIN_ENT bytes from devices
                 * until entitlement change is served
                 */
                list_for_each_entry(dev_ent, &vio_cmo.device_list, list) {
                        if (!delta)
                                break;

                        viodev = dev_ent->viodev;
                        tmp = 0;
                        if ((viodev->cmo.entitled > viodev->cmo.allocated) &&
                            (viodev->cmo.entitled > VIO_CMO_MIN_ENT))
                                tmp = viodev->cmo.entitled -
                                      max_t(size_t, viodev->cmo.allocated,
                                            VIO_CMO_MIN_ENT);
                        viodev->cmo.entitled -= min(tmp, delta);
                        delta -= min(tmp, delta);
                }
        } else {
                spin_unlock_irqrestore(&vio_cmo.lock, flags);
                return -ENOMEM;
        }

out:
        schedule_delayed_work(&vio_cmo.balance_q, 0);
        spin_unlock_irqrestore(&vio_cmo.lock, flags);
        return 0;
}

/**
 * vio_cmo_balance - Balance entitlement among devices
 *
 * @work: work queue structure for this operation
 *
 * Any system entitlement above the minimum needed for devices, or
 * already allocated to devices, can be distributed to the devices.
 * The list of devices is iterated through to recalculate the desired
 * entitlement level and to determine how much entitlement above the
 * minimum entitlement is allocated to devices.
 *
 * Small chunks of the available entitlement are given to devices until
 * their requirements are fulfilled or there is no entitlement left to give.
 * Upon completion sizes of the reserve and excess pools are calculated.
 *
 * The system minimum entitlement level is also recalculated here.
 * Entitlement will be reserved for devices even after vio_bus_remove to
 * accommodate reloading the driver.  The OF tree is walked to count the
 * number of devices present and this will remove entitlement for devices
 * that have actually left the system after having vio_bus_remove called.
 */
static void vio_cmo_balance(struct work_struct *work)
{
        struct vio_cmo *cmo;
        struct vio_dev *viodev;
        struct vio_cmo_dev_entry *dev_ent;
        unsigned long flags;
        size_t avail = 0, level, chunk, need;
        int devcount = 0, fulfilled;

        cmo = container_of(work, struct vio_cmo, balance_q.work);

        spin_lock_irqsave(&vio_cmo.lock, flags);

        /* Calculate minimum entitlement and fulfill spare */
        cmo->min = vio_cmo_num_OF_devs() * VIO_CMO_MIN_ENT;
        BUG_ON(cmo->min > cmo->entitled);
        cmo->spare = min_t(size_t, VIO_CMO_MIN_ENT, (cmo->entitled - cmo->min));
        cmo->min += cmo->spare;
        cmo->desired = cmo->min;

        /*
         * Determine how much entitlement is available and reset device
         * entitlements
         */
        avail = cmo->entitled - cmo->spare;
        list_for_each_entry(dev_ent, &vio_cmo.device_list, list) {
                viodev = dev_ent->viodev;
                devcount++;
                viodev->cmo.entitled = VIO_CMO_MIN_ENT;
                cmo->desired += (viodev->cmo.desired - VIO_CMO_MIN_ENT);
                avail -= max_t(size_t, viodev->cmo.allocated, VIO_CMO_MIN_ENT);
        }

        /*
         * Having provided each device with the minimum entitlement, loop
         * over the devices portioning out the remaining entitlement
         * until there is nothing left.
         */
        level = VIO_CMO_MIN_ENT;
        while (avail) {
                fulfilled = 0;
                list_for_each_entry(dev_ent, &vio_cmo.device_list, list) {
                        viodev = dev_ent->viodev;

                        if (viodev->cmo.desired <= level) {
                                fulfilled++;
                                continue;
                        }

                        /*
                         * Give the device up to VIO_CMO_BALANCE_CHUNK
                         * bytes of entitlement, but do not exceed the
                         * desired level of entitlement for the device.
                         */
                        chunk = min_t(size_t, avail, VIO_CMO_BALANCE_CHUNK);
                        chunk = min(chunk, (viodev->cmo.desired -
                                            viodev->cmo.entitled));
                        viodev->cmo.entitled += chunk;

                        /*
                         * If the memory for this entitlement increase was
                         * already allocated to the device it does not come
                         * from the available pool being portioned out.
                         */
                        need = max(viodev->cmo.allocated, viodev->cmo.entitled)-
                               max(viodev->cmo.allocated, level);
                        avail -= need;

                }
                if (fulfilled == devcount)
                        break;
                level += VIO_CMO_BALANCE_CHUNK;
        }

        /* Calculate new reserve and excess pool sizes */
        cmo->reserve.size = cmo->min;
        cmo->excess.free = 0;
        cmo->excess.size = 0;
        need = 0;
        list_for_each_entry(dev_ent, &vio_cmo.device_list, list) {
                viodev = dev_ent->viodev;
                /* Calculated reserve size above the minimum entitlement */
                if (viodev->cmo.entitled)
                        cmo->reserve.size += (viodev->cmo.entitled -
                                              VIO_CMO_MIN_ENT);
                /* Calculated used excess entitlement */
                if (viodev->cmo.allocated > viodev->cmo.entitled)
                        need += viodev->cmo.allocated - viodev->cmo.entitled;
        }
        cmo->excess.size = cmo->entitled - cmo->reserve.size;
        cmo->excess.free = cmo->excess.size - need;

        cancel_delayed_work(to_delayed_work(work));
        spin_unlock_irqrestore(&vio_cmo.lock, flags);
}

static void *vio_dma_iommu_alloc_coherent(struct device *dev, size_t size,
                                          dma_addr_t *dma_handle, gfp_t flag,
                                          struct dma_attrs *attrs)
{
        struct vio_dev *viodev = to_vio_dev(dev);
        void *ret;

        if (vio_cmo_alloc(viodev, roundup(size, PAGE_SIZE))) {
                atomic_inc(&viodev->cmo.allocs_failed);
                return NULL;
        }

        ret = dma_iommu_ops.alloc(dev, size, dma_handle, flag, attrs);
        if (unlikely(ret == NULL)) {
                vio_cmo_dealloc(viodev, roundup(size, PAGE_SIZE));
                atomic_inc(&viodev->cmo.allocs_failed);
        }

        return ret;
}

static void vio_dma_iommu_free_coherent(struct device *dev, size_t size,
                                        void *vaddr, dma_addr_t dma_handle,
                                        struct dma_attrs *attrs)
{
        struct vio_dev *viodev = to_vio_dev(dev);

        dma_iommu_ops.free(dev, size, vaddr, dma_handle, attrs);

        vio_cmo_dealloc(viodev, roundup(size, PAGE_SIZE));
}

static dma_addr_t vio_dma_iommu_map_page(struct device *dev, struct page *page,
                                         unsigned long offset, size_t size,
                                         enum dma_data_direction direction,
                                         struct dma_attrs *attrs)
{
        struct vio_dev *viodev = to_vio_dev(dev);
        dma_addr_t ret = DMA_ERROR_CODE;

        if (vio_cmo_alloc(viodev, roundup(size, IOMMU_PAGE_SIZE))) {
                atomic_inc(&viodev->cmo.allocs_failed);
                return ret;
        }

        ret = dma_iommu_ops.map_page(dev, page, offset, size, direction, attrs);
        if (unlikely(dma_mapping_error(dev, ret))) {
                vio_cmo_dealloc(viodev, roundup(size, IOMMU_PAGE_SIZE));
                atomic_inc(&viodev->cmo.allocs_failed);
        }

        return ret;
}

static void vio_dma_iommu_unmap_page(struct device *dev, dma_addr_t dma_handle,
                                     size_t size,
                                     enum dma_data_direction direction,
                                     struct dma_attrs *attrs)
{
        struct vio_dev *viodev = to_vio_dev(dev);

        dma_iommu_ops.unmap_page(dev, dma_handle, size, direction, attrs);

        vio_cmo_dealloc(viodev, roundup(size, IOMMU_PAGE_SIZE));
}

static int vio_dma_iommu_map_sg(struct device *dev, struct scatterlist *sglist,
                                int nelems, enum dma_data_direction direction,
                                struct dma_attrs *attrs)
{
        struct vio_dev *viodev = to_vio_dev(dev);
        struct scatterlist *sgl;
        int ret, count = 0;
        size_t alloc_size = 0;

        for (sgl = sglist; count < nelems; count++, sgl++)
                alloc_size += roundup(sgl->length, IOMMU_PAGE_SIZE);

        if (vio_cmo_alloc(viodev, alloc_size)) {
                atomic_inc(&viodev->cmo.allocs_failed);
                return 0;
        }

        ret = dma_iommu_ops.map_sg(dev, sglist, nelems, direction, attrs);

        if (unlikely(!ret)) {
                vio_cmo_dealloc(viodev, alloc_size);
                atomic_inc(&viodev->cmo.allocs_failed);
                return ret;
        }

        for (sgl = sglist, count = 0; count < ret; count++, sgl++)
                alloc_size -= roundup(sgl->dma_length, IOMMU_PAGE_SIZE);
        if (alloc_size)
                vio_cmo_dealloc(viodev, alloc_size);

        return ret;
}

static void vio_dma_iommu_unmap_sg(struct device *dev,
                struct scatterlist *sglist, int nelems,
                enum dma_data_direction direction,
                struct dma_attrs *attrs)
{
        struct vio_dev *viodev = to_vio_dev(dev);
        struct scatterlist *sgl;
        size_t alloc_size = 0;
        int count = 0;

        for (sgl = sglist; count < nelems; count++, sgl++)
                alloc_size += roundup(sgl->dma_length, IOMMU_PAGE_SIZE);

        dma_iommu_ops.unmap_sg(dev, sglist, nelems, direction, attrs);

        vio_cmo_dealloc(viodev, alloc_size);
}

static int vio_dma_iommu_dma_supported(struct device *dev, u64 mask)
{
        return dma_iommu_ops.dma_supported(dev, mask);
}

static u64 vio_dma_get_required_mask(struct device *dev)
{
        return dma_iommu_ops.get_required_mask(dev);
}

struct dma_map_ops vio_dma_mapping_ops = {
        .alloc             = vio_dma_iommu_alloc_coherent,
        .free              = vio_dma_iommu_free_coherent,
        .map_sg            = vio_dma_iommu_map_sg,
        .unmap_sg          = vio_dma_iommu_unmap_sg,
        .map_page          = vio_dma_iommu_map_page,
        .unmap_page        = vio_dma_iommu_unmap_page,
        .dma_supported     = vio_dma_iommu_dma_supported,
        .get_required_mask = vio_dma_get_required_mask,
};

/**
 * vio_cmo_set_dev_desired - Set desired entitlement for a device
 *
 * @viodev: struct vio_dev for device to alter
 * @new_desired: new desired entitlement level in bytes
 *
 * For use by devices to request a change to their entitlement at runtime or
 * through sysfs.  The desired entitlement level is changed and a balancing
 * of system resources is scheduled to run in the future.
 */
void vio_cmo_set_dev_desired(struct vio_dev *viodev, size_t desired)
{
        unsigned long flags;
        struct vio_cmo_dev_entry *dev_ent;
        int found = 0;

        if (!firmware_has_feature(FW_FEATURE_CMO))
                return;

        spin_lock_irqsave(&vio_cmo.lock, flags);
        if (desired < VIO_CMO_MIN_ENT)
                desired = VIO_CMO_MIN_ENT;

        /*
         * Changes will not be made for devices not in the device list.
         * If it is not in the device list, then no driver is loaded
         * for the device and it can not receive entitlement.
         */
        list_for_each_entry(dev_ent, &vio_cmo.device_list, list)
                if (viodev == dev_ent->viodev) {
                        found = 1;
                        break;
                }
        if (!found) {
                spin_unlock_irqrestore(&vio_cmo.lock, flags);
                return;
        }

        /* Increase/decrease in desired device entitlement */
        if (desired >= viodev->cmo.desired) {
                /* Just bump the bus and device values prior to a balance*/
                vio_cmo.desired += desired - viodev->cmo.desired;
                viodev->cmo.desired = desired;
        } else {
                /* Decrease bus and device values for desired entitlement */
                vio_cmo.desired -= viodev->cmo.desired - desired;
                viodev->cmo.desired = desired;
                /*
                 * If less entitlement is desired than current entitlement, move
                 * any reserve memory in the change region to the excess pool.
                 */
                if (viodev->cmo.entitled > desired) {
                        vio_cmo.reserve.size -= viodev->cmo.entitled - desired;
                        vio_cmo.excess.size += viodev->cmo.entitled - desired;
                        /*
                         * If entitlement moving from the reserve pool to the
                         * excess pool is currently unused, add to the excess
                         * free counter.
                         */
                        if (viodev->cmo.allocated < viodev->cmo.entitled)
                                vio_cmo.excess.free += viodev->cmo.entitled -
                                                       max(viodev->cmo.allocated, desired);
                        viodev->cmo.entitled = desired;
                }
        }
        schedule_delayed_work(&vio_cmo.balance_q, 0);
        spin_unlock_irqrestore(&vio_cmo.lock, flags);
}

/**
 * vio_cmo_bus_probe - Handle CMO specific bus probe activities
 *
 * @viodev - Pointer to struct vio_dev for device
 *
 * Determine the devices IO memory entitlement needs, attempting
 * to satisfy the system minimum entitlement at first and scheduling
 * a balance operation to take care of the rest at a later time.
 *
 * Returns: 0 on success, -EINVAL when device doesn't support CMO, and
 *          -ENOMEM when entitlement is not available for device or
 *          device entry.
 *
 */
static int vio_cmo_bus_probe(struct vio_dev *viodev)
{
        struct vio_cmo_dev_entry *dev_ent;
        struct device *dev = &viodev->dev;
        struct vio_driver *viodrv = to_vio_driver(dev->driver);
        unsigned long flags;
        size_t size;

        /*
         * Check to see that device has a DMA window and configure
         * entitlement for the device.
         */
        if (of_get_property(viodev->dev.of_node,
                            "ibm,my-dma-window", NULL)) {
                /* Check that the driver is CMO enabled and get desired DMA */
                if (!viodrv->get_desired_dma) {
                        dev_err(dev, "%s: device driver does not support CMO\n",
                                __func__);
                        return -EINVAL;
                }

                viodev->cmo.desired = IOMMU_PAGE_ALIGN(viodrv->get_desired_dma(viodev));
                if (viodev->cmo.desired < VIO_CMO_MIN_ENT)
                        viodev->cmo.desired = VIO_CMO_MIN_ENT;
                size = VIO_CMO_MIN_ENT;

                dev_ent = kmalloc(sizeof(struct vio_cmo_dev_entry),
                                  GFP_KERNEL);
                if (!dev_ent)
                        return -ENOMEM;

                dev_ent->viodev = viodev;
                spin_lock_irqsave(&vio_cmo.lock, flags);
                list_add(&dev_ent->list, &vio_cmo.device_list);
        } else {
                viodev->cmo.desired = 0;
                size = 0;
                spin_lock_irqsave(&vio_cmo.lock, flags);
        }

        /*
         * If the needs for vio_cmo.min have not changed since they
         * were last set, the number of devices in the OF tree has
         * been constant and the IO memory for this is already in
         * the reserve pool.
         */
        if (vio_cmo.min == ((vio_cmo_num_OF_devs() + 1) *
                            VIO_CMO_MIN_ENT)) {
                /* Updated desired entitlement if device requires it */
                if (size)
                        vio_cmo.desired += (viodev->cmo.desired -
                                        VIO_CMO_MIN_ENT);
        } else {
                size_t tmp;

                tmp = vio_cmo.spare + vio_cmo.excess.free;
                if (tmp < size) {
                        dev_err(dev, "%s: insufficient free "
                                "entitlement to add device. "
                                "Need %lu, have %lu\n", __func__,
                                size, (vio_cmo.spare + tmp));
                        spin_unlock_irqrestore(&vio_cmo.lock, flags);
                        return -ENOMEM;
                }

                /* Use excess pool first to fulfill request */
                tmp = min(size, vio_cmo.excess.free);
                vio_cmo.excess.free -= tmp;
                vio_cmo.excess.size -= tmp;
                vio_cmo.reserve.size += tmp;

                /* Use spare if excess pool was insufficient */
                vio_cmo.spare -= size - tmp;

                /* Update bus accounting */
                vio_cmo.min += size;
                vio_cmo.desired += viodev->cmo.desired;
        }
        spin_unlock_irqrestore(&vio_cmo.lock, flags);
        return 0;
}

/**
 * vio_cmo_bus_remove - Handle CMO specific bus removal activities
 *
 * @viodev - Pointer to struct vio_dev for device
 *
 * Remove the device from the cmo device list.  The minimum entitlement
 * will be reserved for the device as long as it is in the system.  The
 * rest of the entitlement the device had been allocated will be returned
 * to the system.
 */
static void vio_cmo_bus_remove(struct vio_dev *viodev)
{
        struct vio_cmo_dev_entry *dev_ent;
        unsigned long flags;
        size_t tmp;

        spin_lock_irqsave(&vio_cmo.lock, flags);
        if (viodev->cmo.allocated) {
                dev_err(&viodev->dev, "%s: device had %lu bytes of IO "
                        "allocated after remove operation.\n",
                        __func__, viodev->cmo.allocated);
                BUG();
        }

        /*
         * Remove the device from the device list being maintained for
         * CMO enabled devices.
         */
        list_for_each_entry(dev_ent, &vio_cmo.device_list, list)
                if (viodev == dev_ent->viodev) {
                        list_del(&dev_ent->list);
                        kfree(dev_ent);
                        break;
                }

        /*
         * Devices may not require any entitlement and they do not need
         * to be processed.  Otherwise, return the device's entitlement
         * back to the pools.
         */
        if (viodev->cmo.entitled) {
                /*
                 * This device has not yet left the OF tree, it's
                 * minimum entitlement remains in vio_cmo.min and
                 * vio_cmo.desired
                 */
                vio_cmo.desired -= (viodev->cmo.desired - VIO_CMO_MIN_ENT);

                /*
                 * Save min allocation for device in reserve as long
                 * as it exists in OF tree as determined by later
                 * balance operation
                 */
                viodev->cmo.entitled -= VIO_CMO_MIN_ENT;

                /* Replenish spare from freed reserve pool */
                if (viodev->cmo.entitled && (vio_cmo.spare < VIO_CMO_MIN_ENT)) {
                        tmp = min(viodev->cmo.entitled, (VIO_CMO_MIN_ENT -
                                                         vio_cmo.spare));
                        vio_cmo.spare += tmp;
                        viodev->cmo.entitled -= tmp;
                }

                /* Remaining reserve goes to excess pool */
                vio_cmo.excess.size += viodev->cmo.entitled;
                vio_cmo.excess.free += viodev->cmo.entitled;
                vio_cmo.reserve.size -= viodev->cmo.entitled;

                /*
                 * Until the device is removed it will keep a
                 * minimum entitlement; this will guarantee that
                 * a module unload/load will result in a success.
                 */
                viodev->cmo.entitled = VIO_CMO_MIN_ENT;
                viodev->cmo.desired = VIO_CMO_MIN_ENT;
                atomic_set(&viodev->cmo.allocs_failed, 0);
        }

        spin_unlock_irqrestore(&vio_cmo.lock, flags);
}

static void vio_cmo_set_dma_ops(struct vio_dev *viodev)
{
        set_dma_ops(&viodev->dev, &vio_dma_mapping_ops);
}

/**
 * vio_cmo_bus_init - CMO entitlement initialization at bus init time
 *
 * Set up the reserve and excess entitlement pools based on available
 * system entitlement and the number of devices in the OF tree that
 * require entitlement in the reserve pool.
 */
static void vio_cmo_bus_init(void)
{
        struct hvcall_mpp_data mpp_data;
        int err;

        memset(&vio_cmo, 0, sizeof(struct vio_cmo));
        spin_lock_init(&vio_cmo.lock);
        INIT_LIST_HEAD(&vio_cmo.device_list);
        INIT_DELAYED_WORK(&vio_cmo.balance_q, vio_cmo_balance);

        /* Get current system entitlement */
        err = h_get_mpp(&mpp_data);

        /*
         * On failure, continue with entitlement set to 0, will panic()
         * later when spare is reserved.
         */
        if (err != H_SUCCESS) {
                printk(KERN_ERR "%s: unable to determine system IO "\
                       "entitlement. (%d)\n", __func__, err);
                vio_cmo.entitled = 0;
        } else {
                vio_cmo.entitled = mpp_data.entitled_mem;
        }

        /* Set reservation and check against entitlement */
        vio_cmo.spare = VIO_CMO_MIN_ENT;
        vio_cmo.reserve.size = vio_cmo.spare;
        vio_cmo.reserve.size += (vio_cmo_num_OF_devs() *
                                 VIO_CMO_MIN_ENT);
        if (vio_cmo.reserve.size > vio_cmo.entitled) {
                printk(KERN_ERR "%s: insufficient system entitlement\n",
                       __func__);
                panic("%s: Insufficient system entitlement", __func__);
        }

        /* Set the remaining accounting variables */
        vio_cmo.excess.size = vio_cmo.entitled - vio_cmo.reserve.size;
        vio_cmo.excess.free = vio_cmo.excess.size;
        vio_cmo.min = vio_cmo.reserve.size;
        vio_cmo.desired = vio_cmo.reserve.size;
}

/* sysfs device functions and data structures for CMO */

#define viodev_cmo_rd_attr(name)                                        \
static ssize_t viodev_cmo_##name##_show(struct device *dev,             \
                                        struct device_attribute *attr,  \
                                         char *buf)                     \
{                                                                       \
        return sprintf(buf, "%lu\n", to_vio_dev(dev)->cmo.name);        \
}

static ssize_t viodev_cmo_allocs_failed_show(struct device *dev,
                struct device_attribute *attr, char *buf)
{
        struct vio_dev *viodev = to_vio_dev(dev);
        return sprintf(buf, "%d\n", atomic_read(&viodev->cmo.allocs_failed));
}

static ssize_t viodev_cmo_allocs_failed_reset(struct device *dev,
                struct device_attribute *attr, const char *buf, size_t count)
{
        struct vio_dev *viodev = to_vio_dev(dev);
        atomic_set(&viodev->cmo.allocs_failed, 0);
        return count;
}

static ssize_t viodev_cmo_desired_set(struct device *dev,
                struct device_attribute *attr, const char *buf, size_t count)
{
        struct vio_dev *viodev = to_vio_dev(dev);
        size_t new_desired;
        int ret;

        ret = strict_strtoul(buf, 10, &new_desired);
        if (ret)
                return ret;

        vio_cmo_set_dev_desired(viodev, new_desired);
        return count;
}

viodev_cmo_rd_attr(desired);
viodev_cmo_rd_attr(entitled);
viodev_cmo_rd_attr(allocated);

static ssize_t name_show(struct device *, struct device_attribute *, char *);
static ssize_t devspec_show(struct device *, struct device_attribute *, char *);
static ssize_t modalias_show(struct device *dev, struct device_attribute *attr,
                             char *buf);
static struct device_attribute vio_cmo_dev_attrs[] = {
        __ATTR_RO(name),
        __ATTR_RO(devspec),
        __ATTR_RO(modalias),
        __ATTR(cmo_desired,       S_IWUSR|S_IRUSR|S_IWGRP|S_IRGRP|S_IROTH,
               viodev_cmo_desired_show, viodev_cmo_desired_set),
        __ATTR(cmo_entitled,      S_IRUGO, viodev_cmo_entitled_show,      NULL),
        __ATTR(cmo_allocated,     S_IRUGO, viodev_cmo_allocated_show,     NULL),
        __ATTR(cmo_allocs_failed, S_IWUSR|S_IRUSR|S_IWGRP|S_IRGRP|S_IROTH,
               viodev_cmo_allocs_failed_show, viodev_cmo_allocs_failed_reset),
        __ATTR_NULL
};

/* sysfs bus functions and data structures for CMO */

#define viobus_cmo_rd_attr(name)                                        \
static ssize_t                                                          \
viobus_cmo_##name##_show(struct bus_type *bt, char *buf)                \
{                                                                       \
        return sprintf(buf, "%lu\n", vio_cmo.name);                     \
}

#define viobus_cmo_pool_rd_attr(name, var)                              \
static ssize_t                                                          \
viobus_cmo_##name##_pool_show_##var(struct bus_type *bt, char *buf)     \
{                                                                       \
        return sprintf(buf, "%lu\n", vio_cmo.name.var);                 \
}

static ssize_t viobus_cmo_high_reset(struct bus_type *bt, const char *buf,
                                     size_t count)
{
        unsigned long flags;

        spin_lock_irqsave(&vio_cmo.lock, flags);
        vio_cmo.high = vio_cmo.curr;
        spin_unlock_irqrestore(&vio_cmo.lock, flags);

        return count;
}

viobus_cmo_rd_attr(entitled);
viobus_cmo_pool_rd_attr(reserve, size);
viobus_cmo_pool_rd_attr(excess, size);
viobus_cmo_pool_rd_attr(excess, free);
viobus_cmo_rd_attr(spare);
viobus_cmo_rd_attr(min);
viobus_cmo_rd_attr(desired);
viobus_cmo_rd_attr(curr);
viobus_cmo_rd_attr(high);

static struct bus_attribute vio_cmo_bus_attrs[] = {
        __ATTR(cmo_entitled, S_IRUGO, viobus_cmo_entitled_show, NULL),
        __ATTR(cmo_reserve_size, S_IRUGO, viobus_cmo_reserve_pool_show_size, NULL),
        __ATTR(cmo_excess_size, S_IRUGO, viobus_cmo_excess_pool_show_size, NULL),
        __ATTR(cmo_excess_free, S_IRUGO, viobus_cmo_excess_pool_show_free, NULL),
        __ATTR(cmo_spare,   S_IRUGO, viobus_cmo_spare_show,   NULL),
        __ATTR(cmo_min,     S_IRUGO, viobus_cmo_min_show,     NULL),
        __ATTR(cmo_desired, S_IRUGO, viobus_cmo_desired_show, NULL),
        __ATTR(cmo_curr,    S_IRUGO, viobus_cmo_curr_show,    NULL),
        __ATTR(cmo_high,    S_IWUSR|S_IRUSR|S_IWGRP|S_IRGRP|S_IROTH,
               viobus_cmo_high_show, viobus_cmo_high_reset),
        __ATTR_NULL
};

static void vio_cmo_sysfs_init(void)
{
        vio_bus_type.dev_attrs = vio_cmo_dev_attrs;
        vio_bus_type.bus_attrs = vio_cmo_bus_attrs;
}
#else /* CONFIG_PPC_SMLPAR */
/* Dummy functions for iSeries platform */
int vio_cmo_entitlement_update(size_t new_entitlement) { return 0; }
void vio_cmo_set_dev_desired(struct vio_dev *viodev, size_t desired) {}
static int vio_cmo_bus_probe(struct vio_dev *viodev) { return 0; }
static void vio_cmo_bus_remove(struct vio_dev *viodev) {}
static void vio_cmo_set_dma_ops(struct vio_dev *viodev) {}
static void vio_cmo_bus_init(void) {}
static void vio_cmo_sysfs_init(void) { }
#endif /* CONFIG_PPC_SMLPAR */
EXPORT_SYMBOL(vio_cmo_entitlement_update);
EXPORT_SYMBOL(vio_cmo_set_dev_desired);

static struct iommu_table *vio_build_iommu_table(struct vio_dev *dev)
{
        const unsigned char *dma_window;
        struct iommu_table *tbl;
        unsigned long offset, size;

        if (firmware_has_feature(FW_FEATURE_ISERIES))
                return vio_build_iommu_table_iseries(dev);

        dma_window = of_get_property(dev->dev.of_node,
                                  "ibm,my-dma-window", NULL);
        if (!dma_window)
                return NULL;

        tbl = kzalloc(sizeof(*tbl), GFP_KERNEL);
        if (tbl == NULL)
                return NULL;

        of_parse_dma_window(dev->dev.of_node, dma_window,
                            &tbl->it_index, &offset, &size);

        /* TCE table size - measured in tce entries */
        tbl->it_size = size >> IOMMU_PAGE_SHIFT;
        /* offset for VIO should always be 0 */
        tbl->it_offset = offset >> IOMMU_PAGE_SHIFT;
        tbl->it_busno = 0;
        tbl->it_type = TCE_VB;
        tbl->it_blocksize = 16;

        return iommu_init_table(tbl, -1);
}

/**
 * vio_match_device: - Tell if a VIO device has a matching
 *                      VIO device id structure.
 * @ids:        array of VIO device id structures to search in
 * @dev:        the VIO device structure to match against
 *
 * Used by a driver to check whether a VIO device present in the
 * system is in its list of supported devices. Returns the matching
 * vio_device_id structure or NULL if there is no match.
 */
static const struct vio_device_id *vio_match_device(
                const struct vio_device_id *ids, const struct vio_dev *dev)
{
        while (ids->type[0] != '\0') {
                if ((strncmp(dev->type, ids->type, strlen(ids->type)) == 0) &&
                    of_device_is_compatible(dev->dev.of_node,
                                         ids->compat))
                        return ids;
                ids++;
        }
        return NULL;
}

/*
 * Convert from struct device to struct vio_dev and pass to driver.
 * dev->driver has already been set by generic code because vio_bus_match
 * succeeded.
 */
static int vio_bus_probe(struct device *dev)
{
        struct vio_dev *viodev = to_vio_dev(dev);
        struct vio_driver *viodrv = to_vio_driver(dev->driver);
        const struct vio_device_id *id;
        int error = -ENODEV;

        if (!viodrv->probe)
                return error;

        id = vio_match_device(viodrv->id_table, viodev);
        if (id) {
                memset(&viodev->cmo, 0, sizeof(viodev->cmo));
                if (firmware_has_feature(FW_FEATURE_CMO)) {
                        error = vio_cmo_bus_probe(viodev);
                        if (error)
                                return error;
                }
                error = viodrv->probe(viodev, id);
                if (error && firmware_has_feature(FW_FEATURE_CMO))
                        vio_cmo_bus_remove(viodev);
        }

        return error;
}

/* convert from struct device to struct vio_dev and pass to driver. */
static int vio_bus_remove(struct device *dev)
{
        struct vio_dev *viodev = to_vio_dev(dev);
        struct vio_driver *viodrv = to_vio_driver(dev->driver);
        struct device *devptr;
        int ret = 1;

        /*
         * Hold a reference to the device after the remove function is called
         * to allow for CMO accounting cleanup for the device.
         */
        devptr = get_device(dev);

        if (viodrv->remove)
                ret = viodrv->remove(viodev);

        if (!ret && firmware_has_feature(FW_FEATURE_CMO))
                vio_cmo_bus_remove(viodev);

        put_device(devptr);
        return ret;
}

/**
 * vio_register_driver: - Register a new vio driver
 * @drv:        The vio_driver structure to be registered.
 */
int vio_register_driver(struct vio_driver *viodrv)
{
        printk(KERN_DEBUG "%s: driver %s registering\n", __func__,
                viodrv->driver.name);

        /* fill in 'struct driver' fields */
        viodrv->driver.bus = &vio_bus_type;

        return driver_register(&viodrv->driver);
}
EXPORT_SYMBOL(vio_register_driver);

/**
 * vio_unregister_driver - Remove registration of vio driver.
 * @driver:     The vio_driver struct to be removed form registration
 */
void vio_unregister_driver(struct vio_driver *viodrv)
{
        driver_unregister(&viodrv->driver);
}
EXPORT_SYMBOL(vio_unregister_driver);

/* vio_dev refcount hit 0 */
static void __devinit vio_dev_release(struct device *dev)
{
        struct iommu_table *tbl = get_iommu_table_base(dev);

        /* iSeries uses a common table for all vio devices */
        if (!firmware_has_feature(FW_FEATURE_ISERIES) && tbl)
                iommu_free_table(tbl, dev->of_node ?
                        dev->of_node->full_name : dev_name(dev));
        of_node_put(dev->of_node);
        kfree(to_vio_dev(dev));
}

/**
 * vio_register_device_node: - Register a new vio device.
 * @of_node:    The OF node for this device.
 *
 * Creates and initializes a vio_dev structure from the data in
 * of_node and adds it to the list of virtual devices.
 * Returns a pointer to the created vio_dev or NULL if node has
 * NULL device_type or compatible fields.
 */
struct vio_dev *vio_register_device_node(struct device_node *of_node)
{
        struct vio_dev *viodev;
        const unsigned int *unit_address;

        /* we need the 'device_type' property, in order to match with drivers */
        if (of_node->type == NULL) {
                printk(KERN_WARNING "%s: node %s missing 'device_type'\n",
                                __func__,
                                of_node->name ? of_node->name : "<unknown>");
                return NULL;
        }

        unit_address = of_get_property(of_node, "reg", NULL);
        if (unit_address == NULL) {
                printk(KERN_WARNING "%s: node %s missing 'reg'\n",
                                __func__,
                                of_node->name ? of_node->name : "<unknown>");
                return NULL;
        }

        /* allocate a vio_dev for this node */
        viodev = kzalloc(sizeof(struct vio_dev), GFP_KERNEL);
        if (viodev == NULL)
                return NULL;

        viodev->irq = irq_of_parse_and_map(of_node, 0);

        dev_set_name(&viodev->dev, "%x", *unit_address);
        viodev->name = of_node->name;
        viodev->type = of_node->type;
        viodev->unit_address = *unit_address;
        if (firmware_has_feature(FW_FEATURE_ISERIES)) {
                unit_address = of_get_property(of_node,
                                "linux,unit_address", NULL);
                if (unit_address != NULL)
                        viodev->unit_address = *unit_address;
        }
        viodev->dev.of_node = of_node_get(of_node);

        if (firmware_has_feature(FW_FEATURE_CMO))
                vio_cmo_set_dma_ops(viodev);
        else
                set_dma_ops(&viodev->dev, &dma_iommu_ops);
        set_iommu_table_base(&viodev->dev, vio_build_iommu_table(viodev));
        set_dev_node(&viodev->dev, of_node_to_nid(of_node));

        /* init generic 'struct device' fields: */
        viodev->dev.parent = &vio_bus_device.dev;
        viodev->dev.bus = &vio_bus_type;
        viodev->dev.release = vio_dev_release;
        /* needed to ensure proper operation of coherent allocations
         * later, in case driver doesn't set it explicitly */
        dma_set_mask(&viodev->dev, DMA_BIT_MASK(64));
        dma_set_coherent_mask(&viodev->dev, DMA_BIT_MASK(64));

        /* register with generic device framework */
        if (device_register(&viodev->dev)) {
                printk(KERN_ERR "%s: failed to register device %s\n",
                                __func__, dev_name(&viodev->dev));
                put_device(&viodev->dev);
                return NULL;
        }

        return viodev;
}
EXPORT_SYMBOL(vio_register_device_node);

/**
 * vio_bus_init: - Initialize the virtual IO bus
 */
static int __init vio_bus_init(void)
{
        int err;
        struct device_node *node_vroot;

        if (firmware_has_feature(FW_FEATURE_CMO))
                vio_cmo_sysfs_init();

        err = bus_register(&vio_bus_type);
        if (err) {
                printk(KERN_ERR "failed to register VIO bus\n");
                return err;
        }

        /*
         * The fake parent of all vio devices, just to give us
         * a nice directory
         */
        err = device_register(&vio_bus_device.dev);
        if (err) {
                printk(KERN_WARNING "%s: device_register returned %i\n",
                                __func__, err);
                return err;
        }

        if (firmware_has_feature(FW_FEATURE_CMO))
                vio_cmo_bus_init();

        node_vroot = of_find_node_by_name(NULL, "vdevice");
        if (node_vroot) {
                struct device_node *of_node;

                /*
                 * Create struct vio_devices for each virtual device in
                 * the device tree. Drivers will associate with them later.
                 */
                for (of_node = node_vroot->child; of_node != NULL;
                                of_node = of_node->sibling)
                        vio_register_device_node(of_node);
                of_node_put(node_vroot);
        }

        return 0;
}
__initcall(vio_bus_init);

static ssize_t name_show(struct device *dev,
                struct device_attribute *attr, char *buf)
{
        return sprintf(buf, "%s\n", to_vio_dev(dev)->name);
}

static ssize_t devspec_show(struct device *dev,
                struct device_attribute *attr, char *buf)
{
        struct device_node *of_node = dev->of_node;

        return sprintf(buf, "%s\n", of_node ? of_node->full_name : "none");
}

static ssize_t modalias_show(struct device *dev, struct device_attribute *attr,
                             char *buf)
{
        const struct vio_dev *vio_dev = to_vio_dev(dev);
        struct device_node *dn;
        const char *cp;

        dn = dev->of_node;
        if (!dn)
                return -ENODEV;
        cp = of_get_property(dn, "compatible", NULL);
        if (!cp)
                return -ENODEV;

        return sprintf(buf, "vio:T%sS%s\n", vio_dev->type, cp);
}

static struct device_attribute vio_dev_attrs[] = {
        __ATTR_RO(name),
        __ATTR_RO(devspec),
        __ATTR_RO(modalias),
        __ATTR_NULL
};

void __devinit vio_unregister_device(struct vio_dev *viodev)
{
        device_unregister(&viodev->dev);
}
EXPORT_SYMBOL(vio_unregister_device);

static int vio_bus_match(struct device *dev, struct device_driver *drv)
{
        const struct vio_dev *vio_dev = to_vio_dev(dev);
        struct vio_driver *vio_drv = to_vio_driver(drv);
        const struct vio_device_id *ids = vio_drv->id_table;

        return (ids != NULL) && (vio_match_device(ids, vio_dev) != NULL);
}

static int vio_hotplug(struct device *dev, struct kobj_uevent_env *env)
{
        const struct vio_dev *vio_dev = to_vio_dev(dev);
        struct device_node *dn;
        const char *cp;

        dn = dev->of_node;
        if (!dn)
                return -ENODEV;
        cp = of_get_property(dn, "compatible", NULL);
        if (!cp)
                return -ENODEV;

        add_uevent_var(env, "MODALIAS=vio:T%sS%s", vio_dev->type, cp);
        return 0;
}

static struct bus_type vio_bus_type = {
        .name = "vio",
        .dev_attrs = vio_dev_attrs,
        .uevent = vio_hotplug,
        .match = vio_bus_match,
        .probe = vio_bus_probe,
        .remove = vio_bus_remove,
};

/**
 * vio_get_attribute: - get attribute for virtual device
 * @vdev:       The vio device to get property.
 * @which:      The property/attribute to be extracted.
 * @length:     Pointer to length of returned data size (unused if NULL).
 *
 * Calls prom.c's of_get_property() to return the value of the
 * attribute specified by @which
*/
const void *vio_get_attribute(struct vio_dev *vdev, char *which, int *length)
{
        return of_get_property(vdev->dev.of_node, which, length);
}
EXPORT_SYMBOL(vio_get_attribute);

#ifdef CONFIG_PPC_PSERIES
/* vio_find_name() - internal because only vio.c knows how we formatted the
 * kobject name
 */
static struct vio_dev *vio_find_name(const char *name)
{
        struct device *found;

        found = bus_find_device_by_name(&vio_bus_type, NULL, name);
        if (!found)
                return NULL;

        return to_vio_dev(found);
}

/**
 * vio_find_node - find an already-registered vio_dev
 * @vnode: device_node of the virtual device we're looking for
 */
struct vio_dev *vio_find_node(struct device_node *vnode)
{
        const uint32_t *unit_address;
        char kobj_name[20];

        /* construct the kobject name from the device node */
        unit_address = of_get_property(vnode, "reg", NULL);
        if (!unit_address)
                return NULL;
        snprintf(kobj_name, sizeof(kobj_name), "%x", *unit_address);

        return vio_find_name(kobj_name);
}
EXPORT_SYMBOL(vio_find_node);

int vio_enable_interrupts(struct vio_dev *dev)
{
        int rc = h_vio_signal(dev->unit_address, VIO_IRQ_ENABLE);
        if (rc != H_SUCCESS)
                printk(KERN_ERR "vio: Error 0x%x enabling interrupts\n", rc);
        return rc;
}
EXPORT_SYMBOL(vio_enable_interrupts);

int vio_disable_interrupts(struct vio_dev *dev)
{
        int rc = h_vio_signal(dev->unit_address, VIO_IRQ_DISABLE);
        if (rc != H_SUCCESS)
                printk(KERN_ERR "vio: Error 0x%x disabling interrupts\n", rc);
        return rc;
}
EXPORT_SYMBOL(vio_disable_interrupts);
#endif /* CONFIG_PPC_PSERIES */