diff --git a/README.md b/README.md
index 7774718..db8b873 100644
--- a/README.md
+++ b/README.md
@@ -48,6 +48,19 @@
 make install
 ```
 
+#### Building fmtlib
+
+Check out the [fmtlib source](https://github.com/fmtlib/fmt).
+
+Then run these commands in the source directory.
+
+```
+mkdir build && cd build
+cmake ..
+make
+make install
+```
+
 #### Building stdplus
 
 Check out the [stdplus source](https://github.com/openbmc/stdplus).
diff --git a/configure.ac b/configure.ac
index 94ed8b7..0ed6517 100644
--- a/configure.ac
+++ b/configure.ac
@@ -128,6 +128,18 @@
         [],
         [AC_MSG_ERROR([Could not find libpciaccess... pciaccess package required])]
     )
+    PKG_CHECK_MODULES(
+        [STDPLUS],
+        [stdplus],
+        [],
+        [AC_MSG_ERROR([Could not find stdplus... openbmc/stdplus package required])]
+    )
+    PKG_CHECK_MODULES(
+        [FMT],
+        [fmt],
+        [],
+        [AC_MSG_ERROR([Could not find fmt... fmtlib/fmt package required])]
+    )
 ])
 
 # These packages are required for both the BMC and the host-tool.
diff --git a/tools/Makefile.am b/tools/Makefile.am
index f63a112..9c41e1b 100644
--- a/tools/Makefile.am
+++ b/tools/Makefile.am
@@ -7,12 +7,20 @@
 	$(CODE_COVERAGE_CXXFLAGS)
 
 noinst_LTLIBRARIES = libupdater.la
-libupdater_la_LDFLAGS = -static $(CODE_COVERAGE_LIBS) $(IPMIBLOB_LIBS) $(PCIACCESS_LIBS)
+libupdater_la_LDFLAGS = \
+	-static \
+	$(CODE_COVERAGE_LIBS) \
+	$(FMT_LIBS) \
+	$(IPMIBLOB_LIBS) \
+	$(PCIACCESS_LIBS) \
+	$(STDPLUS_LIBS)
 libupdater_la_CXXFLAGS = \
 	-I$(top_srcdir) \
 	$(CODE_COVERAGE_CXXFLAGS) \
+	$(FMT_CFLAGS) \
 	$(IPMIBLOB_CFLAGS) \
-	$(PCIACCESS_CFLAGS)
+	$(PCIACCESS_CFLAGS) \
+	$(STDPLUS_CFLAGS)
 libupdater_la_SOURCES = \
 	updater.cpp \
 	handler.cpp \
diff --git a/tools/main.cpp b/tools/main.cpp
index dd43c11..3876844 100644
--- a/tools/main.cpp
+++ b/tools/main.cpp
@@ -20,6 +20,7 @@
 #include "net.hpp"
 #include "p2a.hpp"
 #include "pci.hpp"
+#include "pciaccess.hpp"
 #include "progress.hpp"
 #include "tool_errors.hpp"
 #include "updater.hpp"
@@ -249,9 +250,9 @@
         }
         else if (interface == IPMIPCI)
         {
-            auto& pci = host_tool::PciUtilImpl::getInstance();
-            handler = std::make_unique<host_tool::P2aDataHandler>(
-                &blob, &devmem, &pci, &progress);
+            auto& pci = host_tool::PciAccessImpl::getInstance();
+            handler = std::make_unique<host_tool::P2aDataHandler>(&blob, &pci,
+                                                                  &progress);
         }
 
         if (!handler)
diff --git a/tools/p2a.cpp b/tools/p2a.cpp
index 9de60f0..c18df99 100644
--- a/tools/p2a.cpp
+++ b/tools/p2a.cpp
@@ -19,8 +19,12 @@
 #include "data.hpp"
 #include "flags.hpp"
 #include "pci.hpp"
+#include "tool_errors.hpp"
+
+#include <fmt/format.h>
 
 #include <ipmiblob/blob_errors.hpp>
+#include <stdplus/handle/managed.hpp>
 
 #include <cstdint>
 #include <cstring>
@@ -32,221 +36,99 @@
 
 namespace
 {
-void disablePciBridge(HostIoInterface* io, std::size_t address)
-{
-    /* Read current value, and just blindly unset the bit. */
-    std::uint32_t value;
-    if (!io->read(address + aspeedP2aConfig, sizeof(value), &value))
-    {
-        return;
-    }
 
-    value &= ~p2ABridgeEnabled;
-    io->write(address + aspeedP2aConfig, sizeof(value), &value);
+/** @brief RAII wrapper and its destructor for opening a file descriptor */
+static void closeFd(int&& fd, const internal::Sys* const& sys)
+{
+    sys->close(fd);
 }
+using Fd = stdplus::Managed<int, const internal::Sys* const>::Handle<closeFd>;
 
 } // namespace
 
 bool P2aDataHandler::sendContents(const std::string& input,
                                   std::uint16_t session)
 {
-    PciDevice result;
-    PciFilter filter;
-    bool found = false;
-    pciaddr_t bar;
-    bool returnValue = false;
-    int inputFd = -1;
+    std::unique_ptr<PciBridgeIntf> bridge;
     ipmi_flash::PciConfigResponse pciResp;
     std::int64_t fileSize;
-    std::unique_ptr<std::uint8_t[]> readBuffer;
 
-    std::uint16_t pciDeviceVID;
-    std::uint16_t pciDeviceDID;
-    std::uint32_t p2aOffset;
-    std::uint32_t p2aLength;
-
-    for (auto device : PCIDeviceList)
+    try
     {
-        filter.vid = device.VID;
-        filter.did = device.DID;
-
-        /* Find the PCI device entry we want. */
-        auto output = pci->getPciDevices(filter);
-        for (const auto& d : output)
-        {
-            std::fprintf(stderr, "[0x%x 0x%x] \n", d.vid, d.did);
-
-            /* Verify it's a memory-based bar. */
-            bar = d.bars[device.bar];
-
-            if ((bar & PCI_BASE_ADDRESS_SPACE) == PCI_BASE_ADDRESS_SPACE_IO)
-            {
-                /* We want it to not be IO-based access. */
-                continue;
-            }
-
-            /* For now capture the entire device even if we're only using BAR0
-             */
-            result = d;
-            found = true;
-            break;
-        }
-
-        if (found)
-        {
-            std::fprintf(stderr, "Find [0x%x 0x%x] \n", device.VID, device.DID);
-            std::fprintf(stderr, "bar%u[0x%x] \n", device.bar,
-                         (unsigned int)bar);
-            pciDeviceVID = device.VID;
-            pciDeviceDID = device.DID;
-            p2aOffset = device.Offset;
-            p2aLength = device.Length;
-            break;
-        }
+        bridge = std::make_unique<NuvotonPciBridge>(pci);
     }
+    catch (NotFoundException& e)
+    {}
 
-    if (!found)
+    try
     {
-        return false;
+        bridge = std::make_unique<AspeedPciBridge>(pci);
     }
+    catch (NotFoundException& e)
+    {}
 
-    std::fprintf(stderr, "\n");
-
-    /* We sent the open command before this, so the window should be open and
-     * the bridge enabled on the BMC.
-     */
-    if (pciDeviceVID == aspeedPciDeviceInfo.VID &&
-        pciDeviceDID == aspeedPciDeviceInfo.DID)
+    if (!bridge)
     {
-        std::uint32_t value;
-        if (!io->read(bar + aspeedP2aConfig, sizeof(value), &value))
-        {
-            std::fprintf(stderr, "PCI config read failed\n");
-            return false;
-        }
-
-        if (0 == (value & p2ABridgeEnabled))
-        {
-            std::fprintf(stderr, "Bridge not enabled - Enabling from host\n");
-
-            value |= p2ABridgeEnabled;
-            if (!io->write(bar + aspeedP2aConfig, sizeof(value), &value))
-            {
-                std::fprintf(stderr, "PCI config write failed\n");
-                return false;
-            }
-        }
-
-        /* From this point down we need to disable the bridge. */
-        std::fprintf(stderr, "The bridge is enabled!\n");
+        throw NotFoundException("supported PCI device");
     }
 
     /* Read the configuration via blobs metadata (stat). */
     ipmiblob::StatResponse stat = blob->getStat(session);
     if (stat.metadata.size() != sizeof(ipmi_flash::PciConfigResponse))
     {
-        std::fprintf(stderr, "Didn't receive expected size of metadata for "
-                             "PCI Configuration response\n");
-        goto exit;
+        throw ToolException("Didn't receive expected size of metadata for "
+                            "PCI Configuration response");
     }
 
     std::memcpy(&pciResp, stat.metadata.data(), sizeof(pciResp));
-    std::fprintf(stderr, "Received address: 0x%x\n", pciResp.address);
-
-    if (pciDeviceVID == aspeedPciDeviceInfo.VID &&
-        pciDeviceDID == aspeedPciDeviceInfo.DID)
-    {
-        /* Configure the mmio to point there. */
-        if (!io->write(bar + aspeedP2aBridge, sizeof(pciResp.address),
-                       &pciResp.address))
-        {
-            // Failed to set it up, so fall back.
-            std::fprintf(stderr, "Failed to update the bridge address\n");
-            goto exit;
-        }
-    }
+    bridge->configure(pciResp);
 
     /* For data blocks in 64kb, stage data, and send blob write command. */
-    inputFd = sys->open(input.c_str(), 0);
-    if (inputFd < 0)
+    Fd inputFd(sys->open(input.c_str(), 0), sys);
+    if (*inputFd < 0)
     {
-        std::fprintf(stderr, "Unable to open file: '%s'\n", input.c_str());
-        goto exit;
+        (void)inputFd.release();
+        throw internal::errnoException(
+            fmt::format("Error opening file '{}'", input));
     }
 
     fileSize = sys->getSize(input.c_str());
     if (fileSize == 0)
     {
-        std::fprintf(stderr, "Zero-length file, or other file access error\n");
-        goto exit;
+        throw ToolException("Zero-length file, or other file access error");
     }
 
     progress->start(fileSize);
 
-    readBuffer = std::make_unique<std::uint8_t[]>(p2aLength);
-    if (nullptr == readBuffer)
-    {
-        std::fprintf(stderr, "Unable to allocate memory for read buffer.\n");
-        goto exit;
-    }
+    std::vector<std::uint8_t> readBuffer(bridge->getDataLength());
 
-    try
-    {
-        int bytesRead = 0;
-        std::uint32_t offset = 0;
+    int bytesRead = 0;
+    std::uint32_t offset = 0;
 
-        do
+    do
+    {
+        bytesRead = sys->read(*inputFd, readBuffer.data(), readBuffer.size());
+        if (bytesRead > 0)
         {
-            bytesRead = sys->read(inputFd, readBuffer.get(), p2aLength);
-            if (bytesRead > 0)
-            {
-                /* TODO: Will likely need to store an rv somewhere to know when
-                 * we're exiting from failure.
-                 */
-                if (!io->write(bar + p2aOffset, bytesRead, readBuffer.get()))
-                {
-                    std::fprintf(stderr,
-                                 "Failed to write to region in memory!\n");
-                    goto exit;
-                }
+            bridge->write(stdplus::span<const std::uint8_t>(readBuffer.data(),
+                                                            bytesRead));
 
-                /* Ok, so the data is staged, now send the blob write with the
-                 * details.
-                 */
-                struct ipmi_flash::ExtChunkHdr chunk;
-                chunk.length = bytesRead;
-                std::vector<std::uint8_t> chunkBytes(sizeof(chunk));
-                std::memcpy(chunkBytes.data(), &chunk, sizeof(chunk));
+            /* Ok, so the data is staged, now send the blob write with the
+             * details.
+             */
+            struct ipmi_flash::ExtChunkHdr chunk;
+            chunk.length = bytesRead;
+            std::vector<std::uint8_t> chunkBytes(sizeof(chunk));
+            std::memcpy(chunkBytes.data(), &chunk, sizeof(chunk));
 
-                /* This doesn't return anything on success. */
-                blob->writeBytes(session, offset, chunkBytes);
-                offset += bytesRead;
-                progress->updateProgress(bytesRead);
-            }
-        } while (bytesRead > 0);
-    }
-    catch (const ipmiblob::BlobException& b)
-    {
-        goto exit;
-    }
+            /* This doesn't return anything on success. */
+            blob->writeBytes(session, offset, chunkBytes);
+            offset += bytesRead;
+            progress->updateProgress(bytesRead);
+        }
+    } while (bytesRead > 0);
 
-    /* defaults to failure. */
-    returnValue = true;
-
-exit:
-    /* disable ASPEED PCI bridge. */
-    if (pciDeviceVID == aspeedPciDeviceInfo.VID &&
-        pciDeviceDID == aspeedPciDeviceInfo.DID)
-    {
-        disablePciBridge(io, bar);
-    }
-
-    /* close input file. */
-    if (inputFd != -1)
-    {
-        sys->close(inputFd);
-    }
-    return returnValue;
+    return true;
 }
 
 } // namespace host_tool
diff --git a/tools/p2a.hpp b/tools/p2a.hpp
index 1d1cb2d..08153d2 100644
--- a/tools/p2a.hpp
+++ b/tools/p2a.hpp
@@ -2,7 +2,6 @@
 
 #include "interface.hpp"
 #include "internal/sys.hpp"
-#include "io.hpp"
 #include "pci.hpp"
 #include "progress.hpp"
 
@@ -11,30 +10,17 @@
 #include <cstdint>
 #include <vector>
 
-constexpr std::size_t aspeedP2aConfig = 0x0f000;
-constexpr std::size_t aspeedP2aBridge = 0x0f004;
-constexpr std::uint32_t p2ABridgeEnabled = 0x1;
-
-struct PciDeviceInfo
-{
-    std::uint16_t VID;
-    std::uint16_t DID;
-    std::size_t Offset;
-    std::size_t Length;
-    std::uint16_t bar;
-};
-
 namespace host_tool
 {
 
 class P2aDataHandler : public DataInterface
 {
   public:
-    P2aDataHandler(ipmiblob::BlobInterface* blob, HostIoInterface* io,
-                   PciUtilInterface* pci, ProgressInterface* progress,
+    P2aDataHandler(ipmiblob::BlobInterface* blob, const PciAccess* pci,
+                   ProgressInterface* progress,
                    const internal::Sys* sys = &internal::sys_impl) :
         blob(blob),
-        io(io), pci(pci), progress(progress), sys(sys)
+        pci(pci), progress(progress), sys(sys)
     {}
 
     bool sendContents(const std::string& input, std::uint16_t session) override;
@@ -45,16 +31,9 @@
 
   private:
     ipmiblob::BlobInterface* blob;
-    HostIoInterface* io;
-    PciUtilInterface* pci;
+    const PciAccess* pci;
     ProgressInterface* progress;
     const internal::Sys* sys;
-
-    constexpr struct PciDeviceInfo static aspeedPciDeviceInfo = {
-        0x1a03, 0x2000, 0x10000, 0x10000, 1};
-    constexpr struct PciDeviceInfo static nuvotonPciDeviceInfo = {
-        0x1050, 0x0750, 0x0, 0x4000, 0};
-    const std::vector<PciDeviceInfo> PCIDeviceList = {aspeedPciDeviceInfo,
-                                                      nuvotonPciDeviceInfo};
 };
+
 } // namespace host_tool
diff --git a/tools/pci.cpp b/tools/pci.cpp
index 7fa4d59..6e9cfe4 100644
--- a/tools/pci.cpp
+++ b/tools/pci.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright 2019 Google Inc.
+ * Copyright 2020 Google Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,58 +16,141 @@
 
 #include "pci.hpp"
 
+#include "tool_errors.hpp"
+
 extern "C"
 {
 #include <pciaccess.h>
 } // extern "C"
 
-#include <linux/pci_regs.h>
+#include <fmt/format.h>
+
+#include <stdplus/handle/managed.hpp>
 
 #include <cstring>
-#include <optional>
-#include <vector>
+#include <system_error>
 
 namespace host_tool
 {
 
-std::vector<PciDevice>
-    PciUtilImpl::getPciDevices(std::optional<PciFilter> filter)
+namespace
 {
-    struct pci_id_match match = {PCI_MATCH_ANY, PCI_MATCH_ANY, PCI_MATCH_ANY,
-                                 PCI_MATCH_ANY};
-    std::vector<PciDevice> results;
 
-    if (filter.has_value())
+/** @brief RAII wrapper and its destructor for creating a pci_device_iterator */
+static void closeIt(struct pci_device_iterator*&& it,
+                    const PciAccess* const& pci)
+{
+    pci->pci_iterator_destroy(it);
+}
+using It = stdplus::Managed<struct pci_device_iterator*,
+                            const PciAccess* const>::Handle<closeIt>;
+
+} // namespace
+
+PciAccessBridge::PciAccessBridge(const struct pci_id_match* match, int bar,
+                                 std::size_t dataOffset, std::size_t dataLength,
+                                 const PciAccess* pci) :
+    dataOffset(dataOffset),
+    dataLength(dataLength), pci(pci)
+{
+    It it(pci->pci_id_match_iterator_create(match), pci);
+
+    while ((dev = pci->pci_device_next(*it)))
     {
-        match.vendor_id = filter.value().vid;
-        match.device_id = filter.value().did;
-    }
-
-    auto it = pci_id_match_iterator_create(&match);
-    struct pci_device* dev;
-
-    while ((dev = pci_device_next(it)))
-    {
-        PciDevice item;
-
-        pci_device_probe(dev);
-
-        item.bus = dev->bus;
-        item.dev = dev->dev;
-        item.func = dev->func;
-        item.vid = dev->vendor_id;
-        item.did = dev->device_id;
-
-        for (int i = 0; i < PCI_STD_NUM_BARS; i++)
+        int ret = pci->pci_device_probe(dev);
+        if (ret)
         {
-            item.bars[i] = dev->regions[i].base_addr;
+            throw std::system_error(ret, std::generic_category(),
+                                    "Error probing PCI device");
         }
 
-        results.push_back(item);
+        /* Verify it's a memory-based bar. */
+        if (!dev->regions[bar].is_IO)
+            break;
     }
 
-    pci_iterator_destroy(it);
-    return results;
+    if (!dev)
+    {
+        throw NotFoundException(fmt::format(
+            "PCI device {:#04x}:{:#04x}", match->vendor_id, match->device_id));
+    }
+
+    std::fprintf(stderr, "Find [0x%x 0x%x] \n", match->vendor_id,
+                 match->device_id);
+    std::fprintf(stderr, "bar%d[0x%x] \n", bar,
+                 static_cast<unsigned int>(dev->regions[bar].base_addr));
+
+    size = dev->regions[bar].size;
+    int ret = pci->pci_device_map_range(
+        dev, dev->regions[bar].base_addr, dev->regions[bar].size,
+        PCI_DEV_MAP_FLAG_WRITABLE, reinterpret_cast<void**>(&addr));
+    if (ret)
+    {
+        throw std::system_error(ret, std::generic_category(),
+                                "Error mapping PCI device memory");
+    }
+}
+
+PciAccessBridge::~PciAccessBridge()
+{
+    int ret = pci->pci_device_unmap_range(dev, addr, size);
+
+    if (ret)
+    {
+        std::fprintf(stderr, "Error while unmapping PCI device memory: %s\n",
+                     std::strerror(ret));
+    }
+}
+
+void PciAccessBridge::write(const stdplus::span<const std::uint8_t> data)
+{
+    if (data.size() > dataLength)
+    {
+        throw ToolException(
+            fmt::format("Write of {} bytes exceeds maximum of {}", data.size(),
+                        dataLength));
+    }
+
+    std::memcpy(addr + dataOffset, data.data(), data.size());
+}
+
+void AspeedPciBridge::enableBridge()
+{
+    /* We sent the open command before this, so the window should be open and
+     * the bridge enabled on the BMC.
+     */
+    std::uint32_t value;
+    std::memcpy(&value, addr + config, sizeof(value));
+
+    if (0 == (value & bridgeEnabled))
+    {
+        std::fprintf(stderr, "Bridge not enabled - Enabling from host\n");
+
+        value |= bridgeEnabled;
+        std::memcpy(addr + config, &value, sizeof(value));
+    }
+
+    std::fprintf(stderr, "The bridge is enabled!\n");
+}
+
+void AspeedPciBridge::disableBridge()
+{
+    /* addr is valid if the constructor completed */
+
+    /* Read current value, and just blindly unset the bit. */
+    std::uint32_t value;
+    std::memcpy(&value, addr + config, sizeof(value));
+
+    value &= ~bridgeEnabled;
+    std::memcpy(addr + config, &value, sizeof(value));
+}
+
+void AspeedPciBridge::configure(const ipmi_flash::PciConfigResponse& configResp)
+{
+    std::fprintf(stderr, "Received address: 0x%x\n", configResp.address);
+
+    /* Configure the mmio to point there. */
+    std::memcpy(addr + bridge, &configResp.address, sizeof(configResp.address));
 }
 
 } // namespace host_tool
diff --git a/tools/pci.hpp b/tools/pci.hpp
index f421892..7f0cfb7 100644
--- a/tools/pci.hpp
+++ b/tools/pci.hpp
@@ -1,19 +1,30 @@
+/*
+ * Copyright 2020 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
 #pragma once
 
+#include "data.hpp"
 #include "internal/sys.hpp"
-
-extern "C"
-{
-#include <pciaccess.h>
-} // extern "C"
+#include "pciaccess.hpp"
 
 #include <linux/pci_regs.h>
 
-#include <cstdint>
-#include <memory>
-#include <optional>
-#include <vector>
+#include <stdplus/types.hpp>
 
+// Some versions of the linux/pci_regs.h header don't define this
 #ifndef PCI_STD_NUM_BARS
 #define PCI_STD_NUM_BARS 6
 #endif // !PCI_STD_NUM_BARS
@@ -21,76 +32,113 @@
 namespace host_tool
 {
 
-/* The ASPEED AST2400 & AST2500 have the same VIDDID. */
-
-/**
- * The PciDevice structure is a copy of the information to uniquely identify a
- * PCI device.
- */
-struct PciDevice
-{
-    std::uint16_t vid;
-    std::uint16_t did;
-    std::uint8_t bus;
-    std::uint8_t dev;
-    std::uint8_t func;
-    pciaddr_t bars[PCI_STD_NUM_BARS];
-};
-
-/**
- * The PciFilter structure is a simple mechanism for filtering devices by their
- * vendor and/or device ids.
- */
-struct PciFilter
-{
-    std::uint16_t vid;
-    std::uint16_t did;
-};
-
-class PciUtilInterface
+class PciBridgeIntf
 {
   public:
-    virtual ~PciUtilInterface() = default;
+    virtual ~PciBridgeIntf() = default;
 
-    /**
-     * Get a list of PCI devices from a system.
-     *
-     * @param[in] filter - optional filter for the list.
-     * @return the list of devices.
-     */
-    virtual std::vector<PciDevice>
-        getPciDevices(std::optional<PciFilter> filter = std::nullopt) = 0;
+    virtual void write(const stdplus::span<const std::uint8_t> data) = 0;
+    virtual void configure(const ipmi_flash::PciConfigResponse& config) = 0;
+
+    virtual std::size_t getDataLength() = 0;
 };
 
-class PciUtilImpl : public PciUtilInterface
+class PciAccessBridge : public PciBridgeIntf
 {
   public:
-    static PciUtilImpl& getInstance()
+    virtual ~PciAccessBridge();
+
+    virtual void write(const stdplus::span<const std::uint8_t> data) override;
+    virtual void
+        configure(const ipmi_flash::PciConfigResponse& configResp) override{};
+
+    std::size_t getDataLength() override
     {
-        static PciUtilImpl instance;
-        return instance;
+        return dataLength;
     }
 
-    std::vector<PciDevice>
-        getPciDevices(std::optional<PciFilter> filter = std::nullopt) override;
+  protected:
+    /**
+     * Finds the PCI device matching @a match and saves a reference to it in @a
+     * dev. Also maps the memory region described in BAR number @a bar to
+     * address @a addr,
+     */
+    PciAccessBridge(const struct pci_id_match* match, int bar,
+                    std::size_t dataOffset, std::size_t dataLength,
+                    const PciAccess* pci);
 
-    PciUtilImpl(const PciUtilImpl&) = delete;
-    PciUtilImpl& operator=(const PciUtilImpl&) = delete;
+    struct pci_device* dev = nullptr;
+    std::uint8_t* addr = nullptr;
+    std::size_t size = 0;
 
   private:
-    PciUtilImpl()
+    std::size_t dataOffset;
+    std::size_t dataLength;
+
+  protected:
+    const PciAccess* pci;
+};
+
+class NuvotonPciBridge : public PciAccessBridge
+{
+  public:
+    explicit NuvotonPciBridge(const PciAccess* pci) :
+        PciAccessBridge(&match, bar, dataOffset, dataLength, pci)
+    {}
+
+    ~NuvotonPciBridge()
+    {}
+
+  private:
+    static constexpr std::uint32_t vid = 0x1050;
+    static constexpr std::uint32_t did = 0x0750;
+    static constexpr int bar = 0;
+    static constexpr struct pci_id_match match
     {
-        int ret = pci_system_init();
-        if (ret)
-        {
-            throw internal::errnoException("pci_system_init");
-        }
+        vid, did, PCI_MATCH_ANY, PCI_MATCH_ANY
+    };
+
+    static constexpr pciaddr_t bridge = 0x04;
+    static constexpr std::uint8_t bridgeEnabled = 0x02;
+
+    static constexpr std::size_t dataOffset = 0x0;
+    static constexpr std::size_t dataLength = 0x4000;
+};
+
+class AspeedPciBridge : public PciAccessBridge
+{
+  public:
+    explicit AspeedPciBridge(const PciAccess* pci) :
+        PciAccessBridge(&match, bar, dataOffset, dataLength, pci)
+    {
+        enableBridge();
     }
 
-    ~PciUtilImpl()
+    ~AspeedPciBridge()
     {
-        pci_system_cleanup();
+        disableBridge();
     }
+
+    void configure(const ipmi_flash::PciConfigResponse& configResp) override;
+
+  private:
+    static constexpr std::uint32_t vid = 0x1a03;
+    static constexpr std::uint32_t did = 0x2000;
+    static constexpr int bar = 1;
+    static constexpr struct pci_id_match match
+    {
+        vid, did, PCI_MATCH_ANY, PCI_MATCH_ANY
+    };
+
+    static constexpr std::size_t config = 0x0f000;
+    static constexpr std::size_t bridge = 0x0f004;
+    static constexpr std::uint32_t bridgeEnabled = 0x1;
+
+    static constexpr std::size_t dataOffset = 0x10000;
+    static constexpr std::size_t dataLength = 0x10000;
+
+    void enableBridge();
+    void disableBridge();
 };
 
 } // namespace host_tool
diff --git a/tools/test/tools_pci_unittest.cpp b/tools/test/tools_pci_unittest.cpp
index cc67926..00b3eb1 100644
--- a/tools/test/tools_pci_unittest.cpp
+++ b/tools/test/tools_pci_unittest.cpp
@@ -1,5 +1,30 @@
+/*
+ * Copyright 2020 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
 #include "internal_sys_mock.hpp"
+#include "pci.hpp"
 #include "pciaccess_mock.hpp"
+#include "tool_errors.hpp"
+
+#include <stdplus/raw.hpp>
+
+#include <algorithm>
+#include <cstdlib>
+#include <string>
+#include <vector>
 
 #include <gtest/gtest.h>
 
@@ -8,11 +33,456 @@
 namespace
 {
 
-TEST(PciHandleTest, empty)
+using namespace std::string_literals;
+
+using ::testing::Assign;
+using ::testing::ContainerEq;
+using ::testing::DoAll;
+using ::testing::Each;
+using ::testing::Eq;
+using ::testing::InSequence;
+using ::testing::NotNull;
+using ::testing::Return;
+using ::testing::SetArgPointee;
+
+// TODO: switch to ConainerEq for C++20
+MATCHER_P(SpanEq, s, "")
+{
+    return arg.size() == s.size() && !memcmp(arg.data(), s.data(), s.size());
+}
+
+MATCHER_P(PciIdMatch, m, "")
+{
+    return (arg->vendor_id == m->vendor_id && arg->device_id == m->device_id &&
+            arg->subvendor_id == m->subvendor_id &&
+            arg->subdevice_id == m->subdevice_id);
+}
+
+pci_device_iterator* mockIter = reinterpret_cast<pci_device_iterator*>(0x42);
+
+constexpr pciaddr_t mockBaseAddr = 0xdeadbeef;
+constexpr pciaddr_t mockRegionSize = 0x20000;
+
+class Device
+{
+  public:
+    virtual const struct pci_id_match* getMatch() const = 0;
+    virtual struct pci_device getDevice() const = 0;
+    virtual std::unique_ptr<PciBridgeIntf> getBridge(PciAccess* pci) const = 0;
+    virtual std::string getName() const = 0;
+};
+
+class NuvotonDevice : public Device
+{
+  public:
+    const struct pci_id_match* getMatch() const override
+    {
+        return &match;
+    }
+
+    struct pci_device getDevice() const override
+    {
+        struct pci_device dev;
+
+        dev.vendor_id = match.vendor_id;
+        dev.device_id = match.device_id;
+
+        dev.regions[0].is_IO = false;
+        dev.regions[0].base_addr = mockBaseAddr;
+        dev.regions[0].size = mockRegionSize;
+
+        return dev;
+    }
+
+    std::unique_ptr<PciBridgeIntf> getBridge(PciAccess* pci) const override
+    {
+        return std::make_unique<NuvotonPciBridge>(pci);
+    }
+
+    std::string getName() const override
+    {
+        return "Nuvoton"s;
+    }
+
+  private:
+    static constexpr struct pci_id_match match
+    {
+        0x1050, 0x0750, PCI_MATCH_ANY, PCI_MATCH_ANY
+    };
+};
+
+class AspeedDevice : public Device
+{
+  public:
+    const struct pci_id_match* getMatch() const override
+    {
+        return &match;
+    }
+
+    struct pci_device getDevice() const override
+    {
+        struct pci_device dev;
+
+        dev.vendor_id = match.vendor_id;
+        dev.device_id = match.device_id;
+
+        dev.regions[1].is_IO = false;
+        dev.regions[1].base_addr = mockBaseAddr;
+        dev.regions[1].size = mockRegionSize;
+
+        return dev;
+    }
+
+    std::unique_ptr<PciBridgeIntf> getBridge(PciAccess* pci) const override
+    {
+        return std::make_unique<AspeedPciBridge>(pci);
+    }
+
+    std::string getName() const override
+    {
+        return "Aspeed"s;
+    }
+
+    /* Offset to the config region */
+    static constexpr int config = 0x0f000;
+    /* Lower bit determines whether bridge is enabled */
+    static constexpr std::uint8_t bridgeEnabled = 0x01;
+    /* Offset to the MMIO address configuration */
+    static constexpr int bridge = 0x0f004;
+
+  private:
+    static constexpr struct pci_id_match match
+    {
+        0x1a03, 0x2000, PCI_MATCH_ANY, PCI_MATCH_ANY
+    };
+};
+
+NuvotonDevice nuvotonDevice;
+AspeedDevice aspeedDevice;
+
+class PciSetupTest : public testing::TestWithParam<Device*>
+{};
+
+/* Handle device not found */
+TEST_P(PciSetupTest, NotFound)
 {
     PciAccessMock pciMock;
 
-    (void)pciMock;
+    InSequence in;
+
+    EXPECT_CALL(pciMock, pci_id_match_iterator_create(
+                             PciIdMatch(GetParam()->getMatch())))
+        .WillOnce(Return(mockIter));
+    EXPECT_CALL(pciMock, pci_device_next(Eq(mockIter)))
+        .WillOnce(Return(nullptr));
+    EXPECT_CALL(pciMock, pci_iterator_destroy(Eq(mockIter))).Times(1);
+
+    EXPECT_THROW(GetParam()->getBridge(&pciMock), NotFoundException);
+}
+
+/* Test finding device but probe fails */
+TEST_P(PciSetupTest, ProbeFail)
+{
+    PciAccessMock pciMock;
+    struct pci_device dev;
+
+    EXPECT_CALL(pciMock, pci_id_match_iterator_create(
+                             PciIdMatch(GetParam()->getMatch())))
+        .WillOnce(Return(mockIter));
+    EXPECT_CALL(pciMock, pci_device_next(Eq(mockIter)))
+        .WillOnce(Return(&dev))
+        .WillRepeatedly(Return(nullptr));
+
+    EXPECT_CALL(pciMock, pci_device_probe(Eq(&dev))).WillOnce(Return(EFAULT));
+
+    EXPECT_CALL(pciMock, pci_iterator_destroy(Eq(mockIter))).Times(1);
+
+    EXPECT_THROW(GetParam()->getBridge(&pciMock), std::system_error);
+}
+
+/* Test finding device but mapping fails */
+TEST_P(PciSetupTest, MapFail)
+{
+    PciAccessMock pciMock;
+    struct pci_device dev;
+
+    EXPECT_CALL(pciMock, pci_id_match_iterator_create(
+                             PciIdMatch(GetParam()->getMatch())))
+        .WillOnce(Return(mockIter));
+    EXPECT_CALL(pciMock, pci_device_next(Eq(mockIter)))
+        .WillOnce(Return(&dev))
+        .WillRepeatedly(Return(nullptr));
+
+    EXPECT_CALL(pciMock, pci_device_probe(Eq(&dev)))
+        .WillOnce(DoAll(Assign(&dev, GetParam()->getDevice()), Return(0)));
+
+    EXPECT_CALL(pciMock,
+                pci_device_map_range(Eq(&dev), mockBaseAddr, mockRegionSize,
+                                     PCI_DEV_MAP_FLAG_WRITABLE, NotNull()))
+        .WillOnce(Return(EFAULT));
+
+    EXPECT_CALL(pciMock, pci_iterator_destroy(Eq(mockIter))).Times(1);
+
+    EXPECT_THROW(GetParam()->getBridge(&pciMock), std::system_error);
+}
+
+/* Test finding device but unmapping fails */
+TEST_P(PciSetupTest, UnmapFail)
+{
+    PciAccessMock pciMock;
+    struct pci_device dev;
+    std::vector<std::uint8_t> region(mockRegionSize);
+
+    EXPECT_CALL(pciMock, pci_id_match_iterator_create(
+                             PciIdMatch(GetParam()->getMatch())))
+        .WillOnce(Return(mockIter));
+    EXPECT_CALL(pciMock, pci_device_next(Eq(mockIter)))
+        .WillOnce(Return(&dev))
+        .WillRepeatedly(Return(nullptr));
+
+    EXPECT_CALL(pciMock, pci_device_probe(Eq(&dev)))
+        .WillOnce(DoAll(Assign(&dev, GetParam()->getDevice()), Return(0)));
+
+    EXPECT_CALL(pciMock,
+                pci_device_map_range(Eq(&dev), mockBaseAddr, mockRegionSize,
+                                     PCI_DEV_MAP_FLAG_WRITABLE, NotNull()))
+        .WillOnce(DoAll(SetArgPointee<4>(region.data()), Return(0)));
+
+    EXPECT_CALL(pciMock, pci_iterator_destroy(Eq(mockIter))).Times(1);
+    EXPECT_CALL(pciMock, pci_device_unmap_range(Eq(&dev), Eq(region.data()),
+                                                mockRegionSize))
+        .WillOnce(Return(EFAULT));
+
+    // This will print an error but not throw
+    GetParam()->getBridge(&pciMock);
+}
+
+/* Create expectations on pciMock for finding device and mapping memory region
+ */
+void expectSetup(PciAccessMock& pciMock, struct pci_device& dev, Device* param,
+                 std::uint8_t* region)
+{
+    EXPECT_CALL(pciMock,
+                pci_id_match_iterator_create(PciIdMatch(param->getMatch())))
+        .WillOnce(Return(mockIter));
+    EXPECT_CALL(pciMock, pci_device_next(Eq(mockIter)))
+        .WillOnce(Return(&dev))
+        .WillRepeatedly(Return(nullptr));
+
+    EXPECT_CALL(pciMock, pci_device_probe(Eq(&dev)))
+        .WillOnce(DoAll(Assign(&dev, param->getDevice()), Return(0)));
+
+    EXPECT_CALL(pciMock,
+                pci_device_map_range(Eq(&dev), mockBaseAddr, mockRegionSize,
+                                     PCI_DEV_MAP_FLAG_WRITABLE, NotNull()))
+        .WillOnce(DoAll(SetArgPointee<4>(region), Return(0)));
+
+    EXPECT_CALL(pciMock, pci_iterator_destroy(Eq(mockIter))).Times(1);
+    EXPECT_CALL(pciMock,
+                pci_device_unmap_range(Eq(&dev), Eq(region), mockRegionSize))
+        .WillOnce(Return(0));
+}
+
+/* Test finding device and mapping memory region */
+TEST_P(PciSetupTest, Success)
+{
+    PciAccessMock pciMock;
+    struct pci_device dev;
+    std::vector<std::uint8_t> region(mockRegionSize);
+
+    expectSetup(pciMock, dev, GetParam(), region.data());
+
+    GetParam()->getBridge(&pciMock);
+}
+
+INSTANTIATE_TEST_SUITE_P(Default, PciSetupTest,
+                         ::testing::Values(&nuvotonDevice, &aspeedDevice),
+                         [](const testing::TestParamInfo<Device*>& info) {
+                             return info.param->getName();
+                         });
+
+TEST(NuvotonWriteTest, TooLarge)
+{
+    PciAccessMock pciMock;
+    struct pci_device dev;
+    std::vector<std::uint8_t> region(mockRegionSize);
+    std::vector<std::uint8_t> data(0x4001);
+
+    expectSetup(pciMock, dev, &nuvotonDevice, region.data());
+
+    std::unique_ptr<PciBridgeIntf> bridge = nuvotonDevice.getBridge(&pciMock);
+    EXPECT_THROW(bridge->write(stdplus::span<std::uint8_t>(data)),
+                 ToolException);
+}
+
+TEST(NuvotonWriteTest, Success)
+{
+    PciAccessMock pciMock;
+    struct pci_device dev;
+    std::vector<std::uint8_t> region(mockRegionSize);
+    std::vector<std::uint8_t> data(0x4000);
+
+    std::generate(data.begin(), data.end(), std::rand);
+
+    expectSetup(pciMock, dev, &nuvotonDevice, region.data());
+
+    std::unique_ptr<PciBridgeIntf> bridge = nuvotonDevice.getBridge(&pciMock);
+    bridge->write(stdplus::span<std::uint8_t>(data));
+
+    EXPECT_THAT(stdplus::span<uint8_t>(&region[0], data.size()),
+                SpanEq(stdplus::span<uint8_t>(data)));
+}
+
+TEST(NuvotonConfigureTest, Success)
+{
+    PciAccessMock pciMock;
+    struct pci_device dev;
+    std::vector<std::uint8_t> region(mockRegionSize);
+    ipmi_flash::PciConfigResponse config{0x123bea51};
+
+    expectSetup(pciMock, dev, &nuvotonDevice, region.data());
+
+    std::unique_ptr<PciBridgeIntf> bridge = nuvotonDevice.getBridge(&pciMock);
+    bridge->configure(config);
+
+    /* No effect from calling configure(), so the whole region should be 0 */
+    EXPECT_THAT(region, Each(0));
+}
+
+TEST(NuvotonDataLengthTest, Success)
+{
+    PciAccessMock pciMock;
+    struct pci_device dev;
+    std::vector<std::uint8_t> region(mockRegionSize);
+
+    expectSetup(pciMock, dev, &nuvotonDevice, region.data());
+
+    std::unique_ptr<PciBridgeIntf> bridge = nuvotonDevice.getBridge(&pciMock);
+    EXPECT_EQ(bridge->getDataLength(), 0x4000);
+}
+
+TEST(AspeedWriteTest, TooLarge)
+{
+    PciAccessMock pciMock;
+    struct pci_device dev;
+    std::vector<std::uint8_t> region(mockRegionSize);
+    std::vector<std::uint8_t> data(0x10001);
+
+    expectSetup(pciMock, dev, &aspeedDevice, region.data());
+
+    std::unique_ptr<PciBridgeIntf> bridge = aspeedDevice.getBridge(&pciMock);
+    EXPECT_THROW(bridge->write(stdplus::span<std::uint8_t>(data)),
+                 ToolException);
+}
+
+TEST(AspeedWriteTest, Success)
+{
+    PciAccessMock pciMock;
+    struct pci_device dev;
+    std::vector<std::uint8_t> region(mockRegionSize);
+    std::vector<std::uint8_t> data(0x10000);
+
+    std::generate(data.begin(), data.end(), std::rand);
+
+    expectSetup(pciMock, dev, &aspeedDevice, region.data());
+
+    std::unique_ptr<PciBridgeIntf> bridge = aspeedDevice.getBridge(&pciMock);
+    bridge->write(stdplus::span<std::uint8_t>(data));
+
+    EXPECT_THAT(stdplus::span<uint8_t>(&region[0x10000], data.size()),
+                SpanEq(stdplus::span<uint8_t>(data)));
+}
+
+TEST(AspeedConfigureTest, Success)
+{
+    PciAccessMock pciMock;
+    struct pci_device dev;
+    std::vector<std::uint8_t> region(mockRegionSize);
+    ipmi_flash::PciConfigResponse config{0x123bea51};
+
+    expectSetup(pciMock, dev, &aspeedDevice, region.data());
+
+    std::unique_ptr<PciBridgeIntf> bridge = aspeedDevice.getBridge(&pciMock);
+    bridge->configure(config);
+
+    auto configSpan = stdplus::raw::asSpan<uint8_t>(config);
+    EXPECT_THAT(
+        stdplus::span<uint8_t>(&region[AspeedDevice::bridge], sizeof(config)),
+        SpanEq(configSpan));
+}
+
+TEST(AspeedDataLengthTest, Success)
+{
+    PciAccessMock pciMock;
+    struct pci_device dev;
+    std::vector<std::uint8_t> region(mockRegionSize);
+
+    expectSetup(pciMock, dev, &aspeedDevice, region.data());
+
+    std::unique_ptr<PciBridgeIntf> bridge = aspeedDevice.getBridge(&pciMock);
+    EXPECT_EQ(bridge->getDataLength(), 0x10000);
+}
+
+/* Make sure config region is left alone if the bridge is already enabled */
+TEST(AspeedBridgeTest, AlreadyEnabledSuccess)
+{
+    PciAccessMock pciMock;
+    struct pci_device dev;
+    std::vector<std::uint8_t> region(mockRegionSize);
+
+    constexpr std::uint8_t defaultVal = 0x42;
+
+    region[AspeedDevice::config] = defaultVal | AspeedDevice::bridgeEnabled;
+
+    expectSetup(pciMock, dev, &aspeedDevice, region.data());
+
+    std::unique_ptr<PciBridgeIntf> bridge = aspeedDevice.getBridge(&pciMock);
+
+    {
+        std::vector<std::uint8_t> enabledRegion(mockRegionSize);
+        enabledRegion[AspeedDevice::config] =
+            defaultVal | AspeedDevice::bridgeEnabled;
+        EXPECT_THAT(region, ContainerEq(enabledRegion));
+    }
+
+    bridge.reset();
+
+    {
+        std::vector<std::uint8_t> disabledRegion(mockRegionSize);
+        disabledRegion[AspeedDevice::config] = defaultVal;
+        EXPECT_THAT(region, ContainerEq(disabledRegion));
+    }
+}
+
+/* Make sure the bridge gets enabled when needed */
+TEST(AspeedBridgeTest, NotEnabledSuccess)
+{
+    PciAccessMock pciMock;
+    struct pci_device dev;
+    std::vector<std::uint8_t> region(mockRegionSize);
+
+    constexpr std::uint8_t defaultVal = 0x42;
+
+    region[AspeedDevice::config] = defaultVal;
+
+    expectSetup(pciMock, dev, &aspeedDevice, region.data());
+
+    std::unique_ptr<PciBridgeIntf> bridge = aspeedDevice.getBridge(&pciMock);
+
+    {
+        std::vector<std::uint8_t> enabledRegion(mockRegionSize);
+        enabledRegion[AspeedDevice::config] =
+            defaultVal | AspeedDevice::bridgeEnabled;
+        EXPECT_THAT(region, ContainerEq(enabledRegion));
+    }
+
+    bridge.reset();
+
+    {
+        std::vector<std::uint8_t> disabledRegion(mockRegionSize);
+        disabledRegion[AspeedDevice::config] = defaultVal;
+        EXPECT_THAT(region, ContainerEq(disabledRegion));
+    }
 }
 
 } // namespace
diff --git a/tools/tool_errors.hpp b/tools/tool_errors.hpp
index cf898e6..96dfa10 100644
--- a/tools/tool_errors.hpp
+++ b/tools/tool_errors.hpp
@@ -20,4 +20,11 @@
     std::string message;
 };
 
+class NotFoundException : public ToolException
+{
+  public:
+    explicit NotFoundException(const std::string& device) :
+        ToolException(std::string("Couldn't find " + device)){};
+};
+
 } // namespace host_tool