ACPI / PNP: Avoid conflicting resource reservations

[linux/fpc-iii.git] / drivers / acpi / resource.c

/*
 * drivers/acpi/resource.c - ACPI device resources interpretation.
 *
 * Copyright (C) 2012, Intel Corp.
 * Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2 as published
 *  by the Free Software Foundation.
 *
 *  This program is distributed in the hope that it will be useful, but
 *  WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 */

#include <linux/acpi.h>
#include <linux/device.h>
#include <linux/export.h>
#include <linux/ioport.h>
#include <linux/list.h>
#include <linux/slab.h>

#ifdef CONFIG_X86
#define valid_IRQ(i) (((i) != 0) && ((i) != 2))
#else
#define valid_IRQ(i) (true)
#endif

static bool acpi_dev_resource_len_valid(u64 start, u64 end, u64 len, bool io)
{
        u64 reslen = end - start + 1;

        /*
         * CHECKME: len might be required to check versus a minimum
         * length as well. 1 for io is fine, but for memory it does
         * not make any sense at all.
         * Note: some BIOSes report incorrect length for ACPI address space
         * descriptor, so remove check of 'reslen == len' to avoid regression.
         */
        if (len && reslen && start <= end)
                return true;

        pr_debug("ACPI: invalid or unassigned resource %s [%016llx - %016llx] length [%016llx]\n",
                io ? "io" : "mem", start, end, len);

        return false;
}

static void acpi_dev_memresource_flags(struct resource *res, u64 len,
                                       u8 write_protect)
{
        res->flags = IORESOURCE_MEM;

        if (!acpi_dev_resource_len_valid(res->start, res->end, len, false))
                res->flags |= IORESOURCE_DISABLED | IORESOURCE_UNSET;

        if (write_protect == ACPI_READ_WRITE_MEMORY)
                res->flags |= IORESOURCE_MEM_WRITEABLE;
}

static void acpi_dev_get_memresource(struct resource *res, u64 start, u64 len,
                                     u8 write_protect)
{
        res->start = start;
        res->end = start + len - 1;
        acpi_dev_memresource_flags(res, len, write_protect);
}

/**
 * acpi_dev_resource_memory - Extract ACPI memory resource information.
 * @ares: Input ACPI resource object.
 * @res: Output generic resource object.
 *
 * Check if the given ACPI resource object represents a memory resource and
 * if that's the case, use the information in it to populate the generic
 * resource object pointed to by @res.
 *
 * Return:
 * 1) false with res->flags setting to zero: not the expected resource type
 * 2) false with IORESOURCE_DISABLED in res->flags: valid unassigned resource
 * 3) true: valid assigned resource
 */
bool acpi_dev_resource_memory(struct acpi_resource *ares, struct resource *res)
{
        struct acpi_resource_memory24 *memory24;
        struct acpi_resource_memory32 *memory32;
        struct acpi_resource_fixed_memory32 *fixed_memory32;

        switch (ares->type) {
        case ACPI_RESOURCE_TYPE_MEMORY24:
                memory24 = &ares->data.memory24;
                acpi_dev_get_memresource(res, memory24->minimum << 8,
                                         memory24->address_length << 8,
                                         memory24->write_protect);
                break;
        case ACPI_RESOURCE_TYPE_MEMORY32:
                memory32 = &ares->data.memory32;
                acpi_dev_get_memresource(res, memory32->minimum,
                                         memory32->address_length,
                                         memory32->write_protect);
                break;
        case ACPI_RESOURCE_TYPE_FIXED_MEMORY32:
                fixed_memory32 = &ares->data.fixed_memory32;
                acpi_dev_get_memresource(res, fixed_memory32->address,
                                         fixed_memory32->address_length,
                                         fixed_memory32->write_protect);
                break;
        default:
                res->flags = 0;
                return false;
        }

        return !(res->flags & IORESOURCE_DISABLED);
}
EXPORT_SYMBOL_GPL(acpi_dev_resource_memory);

static void acpi_dev_ioresource_flags(struct resource *res, u64 len,
                                      u8 io_decode)
{
        res->flags = IORESOURCE_IO;

        if (!acpi_dev_resource_len_valid(res->start, res->end, len, true))
                res->flags |= IORESOURCE_DISABLED | IORESOURCE_UNSET;

        if (res->end >= 0x10003)
                res->flags |= IORESOURCE_DISABLED | IORESOURCE_UNSET;

        if (io_decode == ACPI_DECODE_16)
                res->flags |= IORESOURCE_IO_16BIT_ADDR;
}

static void acpi_dev_get_ioresource(struct resource *res, u64 start, u64 len,
                                    u8 io_decode)
{
        res->start = start;
        res->end = start + len - 1;
        acpi_dev_ioresource_flags(res, len, io_decode);
}

/**
 * acpi_dev_resource_io - Extract ACPI I/O resource information.
 * @ares: Input ACPI resource object.
 * @res: Output generic resource object.
 *
 * Check if the given ACPI resource object represents an I/O resource and
 * if that's the case, use the information in it to populate the generic
 * resource object pointed to by @res.
 *
 * Return:
 * 1) false with res->flags setting to zero: not the expected resource type
 * 2) false with IORESOURCE_DISABLED in res->flags: valid unassigned resource
 * 3) true: valid assigned resource
 */
bool acpi_dev_resource_io(struct acpi_resource *ares, struct resource *res)
{
        struct acpi_resource_io *io;
        struct acpi_resource_fixed_io *fixed_io;

        switch (ares->type) {
        case ACPI_RESOURCE_TYPE_IO:
                io = &ares->data.io;
                acpi_dev_get_ioresource(res, io->minimum,
                                        io->address_length,
                                        io->io_decode);
                break;
        case ACPI_RESOURCE_TYPE_FIXED_IO:
                fixed_io = &ares->data.fixed_io;
                acpi_dev_get_ioresource(res, fixed_io->address,
                                        fixed_io->address_length,
                                        ACPI_DECODE_10);
                break;
        default:
                res->flags = 0;
                return false;
        }

        return !(res->flags & IORESOURCE_DISABLED);
}
EXPORT_SYMBOL_GPL(acpi_dev_resource_io);

static bool acpi_decode_space(struct resource_win *win,
                              struct acpi_resource_address *addr,
                              struct acpi_address64_attribute *attr)
{
        u8 iodec = attr->granularity == 0xfff ? ACPI_DECODE_10 : ACPI_DECODE_16;
        bool wp = addr->info.mem.write_protect;
        u64 len = attr->address_length;
        struct resource *res = &win->res;

        /*
         * Filter out invalid descriptor according to ACPI Spec 5.0, section
         * 6.4.3.5 Address Space Resource Descriptors.
         */
        if ((addr->min_address_fixed != addr->max_address_fixed && len) ||
            (addr->min_address_fixed && addr->max_address_fixed && !len))
                pr_debug("ACPI: Invalid address space min_addr_fix %d, max_addr_fix %d, len %llx\n",
                         addr->min_address_fixed, addr->max_address_fixed, len);

        res->start = attr->minimum;
        res->end = attr->maximum;

        /*
         * For bridges that translate addresses across the bridge,
         * translation_offset is the offset that must be added to the
         * address on the secondary side to obtain the address on the
         * primary side. Non-bridge devices must list 0 for all Address
         * Translation offset bits.
         */
        if (addr->producer_consumer == ACPI_PRODUCER) {
                res->start += attr->translation_offset;
                res->end += attr->translation_offset;
        } else if (attr->translation_offset) {
                pr_debug("ACPI: translation_offset(%lld) is invalid for non-bridge device.\n",
                         attr->translation_offset);
        }

        switch (addr->resource_type) {
        case ACPI_MEMORY_RANGE:
                acpi_dev_memresource_flags(res, len, wp);
                break;
        case ACPI_IO_RANGE:
                acpi_dev_ioresource_flags(res, len, iodec);
                break;
        case ACPI_BUS_NUMBER_RANGE:
                res->flags = IORESOURCE_BUS;
                break;
        default:
                return false;
        }

        win->offset = attr->translation_offset;

        if (addr->producer_consumer == ACPI_PRODUCER)
                res->flags |= IORESOURCE_WINDOW;

        if (addr->info.mem.caching == ACPI_PREFETCHABLE_MEMORY)
                res->flags |= IORESOURCE_PREFETCH;

        return !(res->flags & IORESOURCE_DISABLED);
}

/**
 * acpi_dev_resource_address_space - Extract ACPI address space information.
 * @ares: Input ACPI resource object.
 * @win: Output generic resource object.
 *
 * Check if the given ACPI resource object represents an address space resource
 * and if that's the case, use the information in it to populate the generic
 * resource object pointed to by @win.
 *
 * Return:
 * 1) false with win->res.flags setting to zero: not the expected resource type
 * 2) false with IORESOURCE_DISABLED in win->res.flags: valid unassigned
 *    resource
 * 3) true: valid assigned resource
 */
bool acpi_dev_resource_address_space(struct acpi_resource *ares,
                                     struct resource_win *win)
{
        struct acpi_resource_address64 addr;

        win->res.flags = 0;
        if (ACPI_FAILURE(acpi_resource_to_address64(ares, &addr)))
                return false;

        return acpi_decode_space(win, (struct acpi_resource_address *)&addr,
                                 &addr.address);
}
EXPORT_SYMBOL_GPL(acpi_dev_resource_address_space);

/**
 * acpi_dev_resource_ext_address_space - Extract ACPI address space information.
 * @ares: Input ACPI resource object.
 * @win: Output generic resource object.
 *
 * Check if the given ACPI resource object represents an extended address space
 * resource and if that's the case, use the information in it to populate the
 * generic resource object pointed to by @win.
 *
 * Return:
 * 1) false with win->res.flags setting to zero: not the expected resource type
 * 2) false with IORESOURCE_DISABLED in win->res.flags: valid unassigned
 *    resource
 * 3) true: valid assigned resource
 */
bool acpi_dev_resource_ext_address_space(struct acpi_resource *ares,
                                         struct resource_win *win)
{
        struct acpi_resource_extended_address64 *ext_addr;

        win->res.flags = 0;
        if (ares->type != ACPI_RESOURCE_TYPE_EXTENDED_ADDRESS64)
                return false;

        ext_addr = &ares->data.ext_address64;

        return acpi_decode_space(win, (struct acpi_resource_address *)ext_addr,
                                 &ext_addr->address);
}
EXPORT_SYMBOL_GPL(acpi_dev_resource_ext_address_space);

/**
 * acpi_dev_irq_flags - Determine IRQ resource flags.
 * @triggering: Triggering type as provided by ACPI.
 * @polarity: Interrupt polarity as provided by ACPI.
 * @shareable: Whether or not the interrupt is shareable.
 */
unsigned long acpi_dev_irq_flags(u8 triggering, u8 polarity, u8 shareable)
{
        unsigned long flags;

        if (triggering == ACPI_LEVEL_SENSITIVE)
                flags = polarity == ACPI_ACTIVE_LOW ?
                        IORESOURCE_IRQ_LOWLEVEL : IORESOURCE_IRQ_HIGHLEVEL;
        else
                flags = polarity == ACPI_ACTIVE_LOW ?
                        IORESOURCE_IRQ_LOWEDGE : IORESOURCE_IRQ_HIGHEDGE;

        if (shareable == ACPI_SHARED)
                flags |= IORESOURCE_IRQ_SHAREABLE;

        return flags | IORESOURCE_IRQ;
}
EXPORT_SYMBOL_GPL(acpi_dev_irq_flags);

static void acpi_dev_irqresource_disabled(struct resource *res, u32 gsi)
{
        res->start = gsi;
        res->end = gsi;
        res->flags = IORESOURCE_IRQ | IORESOURCE_DISABLED | IORESOURCE_UNSET;
}

static void acpi_dev_get_irqresource(struct resource *res, u32 gsi,
                                     u8 triggering, u8 polarity, u8 shareable,
                                     bool legacy)
{
        int irq, p, t;

        if (!valid_IRQ(gsi)) {
                acpi_dev_irqresource_disabled(res, gsi);
                return;
        }

        /*
         * In IO-APIC mode, use overrided attribute. Two reasons:
         * 1. BIOS bug in DSDT
         * 2. BIOS uses IO-APIC mode Interrupt Source Override
         *
         * We do this only if we are dealing with IRQ() or IRQNoFlags()
         * resource (the legacy ISA resources). With modern ACPI 5 devices
         * using extended IRQ descriptors we take the IRQ configuration
         * from _CRS directly.
         */
        if (legacy && !acpi_get_override_irq(gsi, &t, &p)) {
                u8 trig = t ? ACPI_LEVEL_SENSITIVE : ACPI_EDGE_SENSITIVE;
                u8 pol = p ? ACPI_ACTIVE_LOW : ACPI_ACTIVE_HIGH;

                if (triggering != trig || polarity != pol) {
                        pr_warning("ACPI: IRQ %d override to %s, %s\n", gsi,
                                   t ? "level" : "edge", p ? "low" : "high");
                        triggering = trig;
                        polarity = pol;
                }
        }

        res->flags = acpi_dev_irq_flags(triggering, polarity, shareable);
        irq = acpi_register_gsi(NULL, gsi, triggering, polarity);
        if (irq >= 0) {
                res->start = irq;
                res->end = irq;
        } else {
                acpi_dev_irqresource_disabled(res, gsi);
        }
}

/**
 * acpi_dev_resource_interrupt - Extract ACPI interrupt resource information.
 * @ares: Input ACPI resource object.
 * @index: Index into the array of GSIs represented by the resource.
 * @res: Output generic resource object.
 *
 * Check if the given ACPI resource object represents an interrupt resource
 * and @index does not exceed the resource's interrupt count (true is returned
 * in that case regardless of the results of the other checks)).  If that's the
 * case, register the GSI corresponding to @index from the array of interrupts
 * represented by the resource and populate the generic resource object pointed
 * to by @res accordingly.  If the registration of the GSI is not successful,
 * IORESOURCE_DISABLED will be set it that object's flags.
 *
 * Return:
 * 1) false with res->flags setting to zero: not the expected resource type
 * 2) false with IORESOURCE_DISABLED in res->flags: valid unassigned resource
 * 3) true: valid assigned resource
 */
bool acpi_dev_resource_interrupt(struct acpi_resource *ares, int index,
                                 struct resource *res)
{
        struct acpi_resource_irq *irq;
        struct acpi_resource_extended_irq *ext_irq;

        switch (ares->type) {
        case ACPI_RESOURCE_TYPE_IRQ:
                /*
                 * Per spec, only one interrupt per descriptor is allowed in
                 * _CRS, but some firmware violates this, so parse them all.
                 */
                irq = &ares->data.irq;
                if (index >= irq->interrupt_count) {
                        acpi_dev_irqresource_disabled(res, 0);
                        return false;
                }
                acpi_dev_get_irqresource(res, irq->interrupts[index],
                                         irq->triggering, irq->polarity,
                                         irq->sharable, true);
                break;
        case ACPI_RESOURCE_TYPE_EXTENDED_IRQ:
                ext_irq = &ares->data.extended_irq;
                if (index >= ext_irq->interrupt_count) {
                        acpi_dev_irqresource_disabled(res, 0);
                        return false;
                }
                acpi_dev_get_irqresource(res, ext_irq->interrupts[index],
                                         ext_irq->triggering, ext_irq->polarity,
                                         ext_irq->sharable, false);
                break;
        default:
                res->flags = 0;
                return false;
        }

        return true;
}
EXPORT_SYMBOL_GPL(acpi_dev_resource_interrupt);

/**
 * acpi_dev_free_resource_list - Free resource from %acpi_dev_get_resources().
 * @list: The head of the resource list to free.
 */
void acpi_dev_free_resource_list(struct list_head *list)
{
        resource_list_free(list);
}
EXPORT_SYMBOL_GPL(acpi_dev_free_resource_list);

struct res_proc_context {
        struct list_head *list;
        int (*preproc)(struct acpi_resource *, void *);
        void *preproc_data;
        int count;
        int error;
};

static acpi_status acpi_dev_new_resource_entry(struct resource_win *win,
                                               struct res_proc_context *c)
{
        struct resource_entry *rentry;

        rentry = resource_list_create_entry(NULL, 0);
        if (!rentry) {
                c->error = -ENOMEM;
                return AE_NO_MEMORY;
        }
        *rentry->res = win->res;
        rentry->offset = win->offset;
        resource_list_add_tail(rentry, c->list);
        c->count++;
        return AE_OK;
}

static acpi_status acpi_dev_process_resource(struct acpi_resource *ares,
                                             void *context)
{
        struct res_proc_context *c = context;
        struct resource_win win;
        struct resource *res = &win.res;
        int i;

        if (c->preproc) {
                int ret;

                ret = c->preproc(ares, c->preproc_data);
                if (ret < 0) {
                        c->error = ret;
                        return AE_CTRL_TERMINATE;
                } else if (ret > 0) {
                        return AE_OK;
                }
        }

        memset(&win, 0, sizeof(win));

        if (acpi_dev_resource_memory(ares, res)
            || acpi_dev_resource_io(ares, res)
            || acpi_dev_resource_address_space(ares, &win)
            || acpi_dev_resource_ext_address_space(ares, &win))
                return acpi_dev_new_resource_entry(&win, c);

        for (i = 0; acpi_dev_resource_interrupt(ares, i, res); i++) {
                acpi_status status;

                status = acpi_dev_new_resource_entry(&win, c);
                if (ACPI_FAILURE(status))
                        return status;
        }

        return AE_OK;
}

/**
 * acpi_dev_get_resources - Get current resources of a device.
 * @adev: ACPI device node to get the resources for.
 * @list: Head of the resultant list of resources (must be empty).
 * @preproc: The caller's preprocessing routine.
 * @preproc_data: Pointer passed to the caller's preprocessing routine.
 *
 * Evaluate the _CRS method for the given device node and process its output by
 * (1) executing the @preproc() rountine provided by the caller, passing the
 * resource pointer and @preproc_data to it as arguments, for each ACPI resource
 * returned and (2) converting all of the returned ACPI resources into struct
 * resource objects if possible.  If the return value of @preproc() in step (1)
 * is different from 0, step (2) is not applied to the given ACPI resource and
 * if that value is negative, the whole processing is aborted and that value is
 * returned as the final error code.
 *
 * The resultant struct resource objects are put on the list pointed to by
 * @list, that must be empty initially, as members of struct resource_entry
 * objects.  Callers of this routine should use %acpi_dev_free_resource_list() to
 * free that list.
 *
 * The number of resources in the output list is returned on success, an error
 * code reflecting the error condition is returned otherwise.
 */
int acpi_dev_get_resources(struct acpi_device *adev, struct list_head *list,
                           int (*preproc)(struct acpi_resource *, void *),
                           void *preproc_data)
{
        struct res_proc_context c;
        acpi_status status;

        if (!adev || !adev->handle || !list_empty(list))
                return -EINVAL;

        if (!acpi_has_method(adev->handle, METHOD_NAME__CRS))
                return 0;

        c.list = list;
        c.preproc = preproc;
        c.preproc_data = preproc_data;
        c.count = 0;
        c.error = 0;
        status = acpi_walk_resources(adev->handle, METHOD_NAME__CRS,
                                     acpi_dev_process_resource, &c);
        if (ACPI_FAILURE(status)) {
                acpi_dev_free_resource_list(list);
                return c.error ? c.error : -EIO;
        }

        return c.count;
}
EXPORT_SYMBOL_GPL(acpi_dev_get_resources);

/**
 * acpi_dev_filter_resource_type - Filter ACPI resource according to resource
 *                                 types
 * @ares: Input ACPI resource object.
 * @types: Valid resource types of IORESOURCE_XXX
 *
 * This is a helper function to support acpi_dev_get_resources(), which filters
 * ACPI resource objects according to resource types.
 */
int acpi_dev_filter_resource_type(struct acpi_resource *ares,
                                  unsigned long types)
{
        unsigned long type = 0;

        switch (ares->type) {
        case ACPI_RESOURCE_TYPE_MEMORY24:
        case ACPI_RESOURCE_TYPE_MEMORY32:
        case ACPI_RESOURCE_TYPE_FIXED_MEMORY32:
                type = IORESOURCE_MEM;
                break;
        case ACPI_RESOURCE_TYPE_IO:
        case ACPI_RESOURCE_TYPE_FIXED_IO:
                type = IORESOURCE_IO;
                break;
        case ACPI_RESOURCE_TYPE_IRQ:
        case ACPI_RESOURCE_TYPE_EXTENDED_IRQ:
                type = IORESOURCE_IRQ;
                break;
        case ACPI_RESOURCE_TYPE_DMA:
        case ACPI_RESOURCE_TYPE_FIXED_DMA:
                type = IORESOURCE_DMA;
                break;
        case ACPI_RESOURCE_TYPE_GENERIC_REGISTER:
                type = IORESOURCE_REG;
                break;
        case ACPI_RESOURCE_TYPE_ADDRESS16:
        case ACPI_RESOURCE_TYPE_ADDRESS32:
        case ACPI_RESOURCE_TYPE_ADDRESS64:
        case ACPI_RESOURCE_TYPE_EXTENDED_ADDRESS64:
                if (ares->data.address.resource_type == ACPI_MEMORY_RANGE)
                        type = IORESOURCE_MEM;
                else if (ares->data.address.resource_type == ACPI_IO_RANGE)
                        type = IORESOURCE_IO;
                else if (ares->data.address.resource_type ==
                         ACPI_BUS_NUMBER_RANGE)
                        type = IORESOURCE_BUS;
                break;
        default:
                break;
        }

        return (type & types) ? 0 : 1;
}
EXPORT_SYMBOL_GPL(acpi_dev_filter_resource_type);

struct reserved_region {
        struct list_head node;
        u64 start;
        u64 end;
};

static LIST_HEAD(reserved_io_regions);
static LIST_HEAD(reserved_mem_regions);

static int request_range(u64 start, u64 end, u8 space_id, unsigned long flags,
                         char *desc)
{
        unsigned int length = end - start + 1;
        struct resource *res;

        res = space_id == ACPI_ADR_SPACE_SYSTEM_IO ?
                request_region(start, length, desc) :
                request_mem_region(start, length, desc);
        if (!res)
                return -EIO;

        res->flags &= ~flags;
        return 0;
}

static int add_region_before(u64 start, u64 end, u8 space_id,
                             unsigned long flags, char *desc,
                             struct list_head *head)
{
        struct reserved_region *reg;
        int error;

        reg = kmalloc(sizeof(*reg), GFP_KERNEL);
        if (!reg)
                return -ENOMEM;

        error = request_range(start, end, space_id, flags, desc);
        if (error)
                return error;

        reg->start = start;
        reg->end = end;
        list_add_tail(&reg->node, head);
        return 0;
}

/**
 * acpi_reserve_region - Reserve an I/O or memory region as a system resource.
 * @start: Starting address of the region.
 * @length: Length of the region.
 * @space_id: Identifier of address space to reserve the region from.
 * @flags: Resource flags to clear for the region after requesting it.
 * @desc: Region description (for messages).
 *
 * Reserve an I/O or memory region as a system resource to prevent others from
 * using it.  If the new region overlaps with one of the regions (in the given
 * address space) already reserved by this routine, only the non-overlapping
 * parts of it will be reserved.
 *
 * Returned is either 0 (success) or a negative error code indicating a resource
 * reservation problem.  It is the code of the first encountered error, but the
 * routine doesn't abort until it has attempted to request all of the parts of
 * the new region that don't overlap with other regions reserved previously.
 *
 * The resources requested by this routine are never released.
 */
int acpi_reserve_region(u64 start, unsigned int length, u8 space_id,
                        unsigned long flags, char *desc)
{
        struct list_head *regions;
        struct reserved_region *reg;
        u64 end = start + length - 1;
        int ret = 0, error = 0;

        if (space_id == ACPI_ADR_SPACE_SYSTEM_IO)
                regions = &reserved_io_regions;
        else if (space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY)
                regions = &reserved_mem_regions;
        else
                return -EINVAL;

        if (list_empty(regions))
                return add_region_before(start, end, space_id, flags, desc, regions);

        list_for_each_entry(reg, regions, node)
                if (reg->start == end + 1) {
                        /* The new region can be prepended to this one. */
                        ret = request_range(start, end, space_id, flags, desc);
                        if (!ret)
                                reg->start = start;

                        return ret;
                } else if (reg->start > end) {
                        /* No overlap.  Add the new region here and get out. */
                        return add_region_before(start, end, space_id, flags,
                                                 desc, &reg->node);
                } else if (reg->end == start - 1) {
                        goto combine;
                } else if (reg->end >= start) {
                        goto overlap;
                }

        /* The new region goes after the last existing one. */
        return add_region_before(start, end, space_id, flags, desc, regions);

 overlap:
        /*
         * The new region overlaps an existing one.
         *
         * The head part of the new region immediately preceding the existing
         * overlapping one can be combined with it right away.
         */
        if (reg->start > start) {
                error = request_range(start, reg->start - 1, space_id, flags, desc);
                if (error)
                        ret = error;
                else
                        reg->start = start;
        }

 combine:
        /*
         * The new region is adjacent to an existing one.  If it extends beyond
         * that region all the way to the next one, it is possible to combine
         * all three of them.
         */
        while (reg->end < end) {
                struct reserved_region *next = NULL;
                u64 a = reg->end + 1, b = end;

                if (!list_is_last(&reg->node, regions)) {
                        next = list_next_entry(reg, node);
                        if (next->start <= end)
                                b = next->start - 1;
                }
                error = request_range(a, b, space_id, flags, desc);
                if (!error) {
                        if (next && next->start == b + 1) {
                                reg->end = next->end;
                                list_del(&next->node);
                                kfree(next);
                        } else {
                                reg->end = end;
                                break;
                        }
                } else if (next) {
                        if (!ret)
                                ret = error;

                        reg = next;
                } else {
                        break;
                }
        }

        return ret ? ret : error;
}
EXPORT_SYMBOL_GPL(acpi_reserve_region);