設定硬體資源

周邊元件互連 (PCI) 裝置會透過各種介面將資源公開給系統，包括中斷、記憶體對應 I/O (MMIO) 暫存器和直接記憶體存取 (DMA) 緩衝區。Fuchsia 驅動程式會透過上層裝置節點的功能存取這些資源。對於 PCI 裝置，父項會提供 fuchsia.hardware.pci/Device FIDL 通訊協定的執行個體，讓驅動程式庫設定裝置。

在本節中，您將新增功能，存取 edu 裝置上的下列 MMIO 暫存器：

地址偏移 註冊 R/W 說明
0x00 身分識別 RO 主要 / 子版本 ID
0x04 卡片有效性檢查 RW 驗證作業發生問題
0x08 階乘計算 RW 計算儲存值的階乘
0x20 狀態 RW 表示作業完成的位元欄位

完成本節後，專案應具有下列目錄結構：

//fuchsia-codelab/qemu_edu/drivers
                  |- BUILD.bazel
                  |- meta
                  |   |- qemu_edu.cml
                  |- edu_device.cc 
                  |- edu_device.h 
                  |- qemu_edu.bind
                  |- qemu_edu.cc
                  |- qemu_edu.h

連線至父項裝置

如要從父項裝置節點存取 fuchsia.hardware.pci/Device 介面，請將 fuchsia.hardware.pci.Service 能力新增至驅動程式庫元件資訊清單：

qemu_edu/drivers/meta/qemu_edu.cml：

{
    include: [
        "syslog/client.shard.cml",
    ],
    program: {
        runner: 'driver',
        binary: 'driver/libqemu_edu.so',
        bind: 'meta/bind/qemu_edu.bindbc',
        // Identifies the device categories, for compatibility tests. This
        // example driver uses the 'misc' category; real drivers should
        // select a more specific category.
        device_categories: [
          { category: 'misc', subcategory: '' },
        ],
    },
    use: [
        { service: 'fuchsia.hardware.pci.Service' },
    ],
}

這可讓驅動程式庫開啟與上層裝置的連線，並存取上層裝置提供的硬體專屬通訊協定。

更新驅動程式庫的 Start() 方法，在驅動程式庫初始化期間存取父項裝置提供的 fuchsia.hardware.pci/Device：

qemu_edu/drivers/qemu_edu.cc：

#include "qemu_edu.h"

#include <lib/driver/component/cpp/driver_export.h>

namespace qemu_edu {
// ...

// Initialize this driver instance
zx::result<> QemuEduDriver::Start() {

  // Connect to the parent device node.
  zx::result connect_result = incoming()->Connect<fuchsia_hardware_pci::Service::Device>("default");
  if (connect_result.is_error()) {
    FDF_SLOG(ERROR, "Failed to open pci service.", KV("status", connect_result.status_string()));
    return connect_result.take_error();
  }

  fdf::info("edu driver loaded successfully");

  return zx::ok();
}

}  // namespace qemu_edu

設定中斷和 MMIO

開啟與 fuchsia.hardware.pci/Device 的連線後，即可開始將必要的裝置資源對應至驅動程式庫。

在專案目錄中建立新的 qemu_edu/drivers/edu_device.h 檔案，並加入以下內容：

qemu_edu/drivers/edu_device.h：

#ifndef FUCHSIA_CODELAB_QEMU_EDU_DEVICE_H_
#define FUCHSIA_CODELAB_QEMU_EDU_DEVICE_H_

#include <fidl/fuchsia.hardware.pci/cpp/wire.h>
#include <lib/async/cpp/irq.h>
#include <lib/driver/mmio/cpp/mmio-buffer.h>
#include <lib/zx/interrupt.h>

namespace edu_device {

// Interacts with the device hardware using a fuchsia.hardware.pci client.
class QemuEduDevice {
 public:
  explicit QemuEduDevice(async_dispatcher_t* dispatcher,
                         fidl::ClientEnd<fuchsia_hardware_pci::Device> pci)
      : dispatcher_(dispatcher), pci_(std::move(pci)) {}

  zx::result<> MapInterruptAndMmio();

 private:
  void HandleIrq(async_dispatcher_t* dispatcher, async::IrqBase* irq, zx_status_t status,
                 const zx_packet_interrupt_t* interrupt);

  async_dispatcher_t* const dispatcher_;

  fidl::WireSyncClient<fuchsia_hardware_pci::Device> pci_;
  std::optional<fdf::MmioBuffer> mmio_;
  zx::interrupt irq_;
  async::IrqMethod<QemuEduDevice, &QemuEduDevice::HandleIrq> irq_method_{this};
  std::optional<fit::callback<void(zx::result<uint32_t>)>> pending_callback_;
};

}  // namespace edu_device

#endif  // FUCHSIA_CODELAB_QEMU_EDU_DEVICE_H_

建立新的 qemu_edu/drivers/edu_device.cc 檔案，並加入下列程式碼來實作 MapInterruptAndMmio() 方法。這個方法會執行下列工作：

  1. 存取適當 PCI 區域的基底位址暫存器 (BAR)。
  2. 擷取區域的 Fuchsia VMO (虛擬記憶體物件)。
  3. 在區域周圍建立 MMIO 緩衝區，存取個別暫存器。
  4. 設定對應至裝置中斷的 Interrupt Request (IRQ)。

qemu_edu/drivers/edu_device.cc：

#include "edu_device.h"

#include <lib/driver/logging/cpp/structured_logger.h>

namespace edu_device {

// Initialize PCI device hardware resources
zx::result<> QemuEduDevice::MapInterruptAndMmio() {
  // Retrieve the Base Address Register (BAR) for PCI Region 0
  auto bar = pci_->GetBar(0);
  if (!bar.ok()) {
    FDF_SLOG(ERROR, "failed to get bar", KV("status", bar.status()));
    return zx::error(bar.status());
  }
  if (bar->is_error()) {
    FDF_SLOG(ERROR, "failed to get bar", KV("status", bar->error_value()));
    return zx::error(bar->error_value());
  }

  // Create a Memory-Mapped I/O (MMIO) region over BAR0
  {
    auto& bar_result = bar->value()->result;
    if (!bar_result.result.is_vmo()) {
      FDF_SLOG(ERROR, "unexpected bar type");
      return zx::error(ZX_ERR_NO_RESOURCES);
    }
    zx::result<fdf::MmioBuffer> mmio = fdf::MmioBuffer::Create(
        0, bar_result.size, std::move(bar_result.result.vmo()), ZX_CACHE_POLICY_UNCACHED_DEVICE);
    if (mmio.is_error()) {
      FDF_SLOG(ERROR, "failed to map mmio", KV("status", mmio.status_value()));
      return mmio.take_error();
    }
    mmio_ = *std::move(mmio);
  }

  // Configure interrupt handling for the device using INTx
  auto result = pci_->SetInterruptMode(fuchsia_hardware_pci::wire::InterruptMode::kLegacy, 1);
  if (!result.ok()) {
    FDF_SLOG(ERROR, "failed configure interrupt mode", KV("status", result.status()));
    return zx::error(result.status());
  }
  if (result->is_error()) {
    FDF_SLOG(ERROR, "failed configure interrupt mode", KV("status", result->error_value()));
    return zx::error(result->error_value());
  }

  // Map the device's interrupt to a system IRQ
  auto interrupt = pci_->MapInterrupt(0);
  if (!interrupt.ok()) {
    FDF_SLOG(ERROR, "failed to map interrupt", KV("status", interrupt.status()));
    return zx::error(interrupt.status());
  }
  if (interrupt->is_error()) {
    FDF_SLOG(ERROR, "failed to map interrupt", KV("status", interrupt->error_value()));
    return zx::error(interrupt->error_value());
  }
  irq_ = std::move(interrupt->value()->interrupt);
  // Start listening for interrupts.
  irq_method_.set_object(irq_.get());
  irq_method_.Begin(dispatcher_);

  return zx::ok();
}

}  // namespace edu_device

將新的裝置資源新增至驅動程式庫類別：

qemu_edu/drivers/qemu_edu.h：

#include <fidl/examples.qemuedu/cpp/wire.h>
#include <lib/driver/component/cpp/driver_base.h>
#include <lib/driver/devfs/cpp/connector.h>

#include "edu_device.h"

namespace qemu_edu {

class QemuEduDriver : public fdf::DriverBase {

 public:
  QemuEduDriver(fdf::DriverStartArgs start_args,
                fdf::UnownedSynchronizedDispatcher driver_dispatcher)
      : fdf::DriverBase("qemu-edu", std::move(start_args), std::move(driver_dispatcher)) {}

  virtual ~QemuEduDriver() = default;

  // Start hook called by the driver factory.
  zx::result<> Start() override;

 private:
  void Serve(fidl::ServerEnd<examples_qemuedu::Device> request);

  fidl::WireSyncClient<fuchsia_driver_framework::Node> node_;
  fidl::WireSyncClient<fuchsia_driver_framework::NodeController> controller_;
  std::shared_ptr<edu_device::QemuEduDevice> device_;
};

}  // namespace qemu_edu

更新驅動程式庫的 Run() 方法，在驅動程式庫初始化期間呼叫新方法：

qemu_edu/drivers/qemu_edu.cc：

// Initialize this driver instance
zx::result<> QemuEduDriver::Start() {

  // Connect to the parent device node.
  zx::result connect_result = incoming()->Connect<fuchsia_hardware_pci::Service::Device>("default");
  if (connect_result.is_error()) {
    FDF_SLOG(ERROR, "Failed to open pci service.", KV("status", connect_result.status_string()));
    return connect_result.take_error();
  }

  // Map hardware resources from the PCI device
  device_ =
      std::make_shared<edu_device::QemuEduDevice>(dispatcher(), std::move(connect_result.value()));
  auto pci_status = device_->MapInterruptAndMmio();
  if (pci_status.is_error()) {
    return pci_status.take_error();
  }

  fdf::info("edu driver loaded successfully");

  return zx::ok();
}

更新驅動程式庫建構設定，加入新的來源檔案，並依附於 fuchsia.hardware.pci 的 FIDL 繫結程式庫：

qemu_edu/drivers/BUILD.bazel：

fuchsia_cc_driver(
    name = "qemu_edu",
    srcs = [
        "edu_device.cc",
        "edu_device.h",
        "qemu_edu.cc",
        "qemu_edu.h",
    ],
    deps = [
        "@fuchsia_sdk//fidl/fuchsia.hardware.pci:fuchsia.hardware.pci_cpp",
        "@fuchsia_sdk//pkg/driver_component_cpp",
        "@fuchsia_sdk//pkg/driver_devfs_cpp",
        "@fuchsia_sdk//pkg/hwreg",
        "@fuchsia_sdk//pkg/driver_mmio_cpp",
    ],
)

讀取裝置暫存器

將基本資源對應至驅動程式庫後，您就能存取個別暫存器。在專案的 qemu_edu/drivers/edu_device.h 檔案中新增下列暫存器定義：

qemu_edu/drivers/edu_device.h：

#include <hwreg/bitfields.h>

#include <fidl/fuchsia.hardware.pci/cpp/wire.h>
#include <lib/async/cpp/irq.h>
#include <lib/driver/mmio/cpp/mmio-buffer.h>
#include <lib/zx/interrupt.h>

namespace edu_device {

// Register offset addresses for edu device MMIO area
constexpr uint32_t kIdentificationOffset = 0x00;
constexpr uint32_t kLivenessCheckOffset = 0x04;
constexpr uint32_t kFactorialComputationOffset = 0x08;
constexpr uint32_t kStatusRegisterOffset = 0x20;
constexpr uint32_t kInterruptStatusRegisterOffset = 0x24;
constexpr uint32_t kInterruptRaiseRegisterOffset = 0x60;
constexpr uint32_t kInterruptAcknowledgeRegisterOffset = 0x64;
constexpr uint32_t kDmaSourceAddressOffset = 0x80;
constexpr uint32_t kDmaDestinationAddressOffset = 0x80;
constexpr uint32_t kDmaTransferCountOffset = 0x90;
constexpr uint32_t kDmaCommandRegisterOffset = 0x98;

class Identification : public hwreg::RegisterBase<Identification, uint32_t> {
 public:
  DEF_FIELD(31, 24, major_version);
  DEF_FIELD(23, 16, minor_version);
  DEF_FIELD(15, 0, edu);

  static auto Get() { return hwreg::RegisterAddr<Identification>(kIdentificationOffset); }
};

class Status : public hwreg::RegisterBase<Status, uint32_t> {
 public:
  DEF_BIT(0, busy);
  DEF_BIT(7, irq_enable);

  static auto Get() { return hwreg::RegisterAddr<Status>(kStatusRegisterOffset); }
};

// Interacts with the device hardware using a fuchsia.hardware.pci client.
class QemuEduDevice {
 public:
  explicit QemuEduDevice(async_dispatcher_t* dispatcher,
                         fidl::ClientEnd<fuchsia_hardware_pci::Device> pci)
      : dispatcher_(dispatcher), pci_(std::move(pci)) {}

  zx::result<> MapInterruptAndMmio();

  void ComputeFactorial(uint32_t input, fit::callback<void(zx::result<uint32_t>)> callback);
  zx::result<uint32_t> LivenessCheck(uint32_t challenge);

  Identification IdentificationRegister() { return Identification::Get().ReadFrom(&*mmio_); }
  Status StatusRegister() { return Status::Get().ReadFrom(&*mmio_); }

 private:
  void HandleIrq(async_dispatcher_t* dispatcher, async::IrqBase* irq, zx_status_t status,
                 const zx_packet_interrupt_t* interrupt);

  async_dispatcher_t* const dispatcher_;

  fidl::WireSyncClient<fuchsia_hardware_pci::Device> pci_;
  std::optional<fdf::MmioBuffer> mmio_;
  zx::interrupt irq_;
  async::IrqMethod<QemuEduDevice, &QemuEduDevice::HandleIrq> irq_method_{this};
  std::optional<fit::callback<void(zx::result<uint32_t>)>> pending_callback_;
};

}  // namespace edu_device

這會將裝置規格中提供的暫存器偏移量宣告為常數。Fuchsia 的 hwreg 程式庫會包裝代表位元欄位的暫存器，方便存取這些暫存器，不必執行個別的位元運算。

在 qemu_edu/drivers/edu_device.cc 中實作下列其他方法，與 MMIO 區域互動，以便讀取資料並寫入相應的 edu 裝置暫存器：

  • ComputeFactorial()：將輸入值寫入階乘運算暫存器，並等待裝置使用中斷訊號非同步發出完成信號。
  • HandleIrq()：從階乘暫存器讀取運算結果，並回報給待處理的回呼。
  • LivenessCheck()：將驗證值寫入動態偵測暫存器，並確認預期結果。

qemu_edu/drivers/edu_device.cc：

#include "edu_device.h"

#include <lib/driver/logging/cpp/structured_logger.h>

namespace edu_device {
// ...

// Write data into the factorial register wait for an interrupt.
void QemuEduDevice::ComputeFactorial(uint32_t input,
                                     fit::callback<void(zx::result<uint32_t>)> callback) {
  if (pending_callback_.has_value()) {
    callback(zx::error(ZX_ERR_SHOULD_WAIT));
  }

  // Tell the device to raise an interrupt after computation.
  auto status = StatusRegister();
  status.set_irq_enable(true);
  status.WriteTo(&*mmio_);

  // Write the value into the factorial register to start computation.
  mmio_->Write32(input, kFactorialComputationOffset);

  // We will receive an interrupt when the computation completes.
  pending_callback_ = std::move(callback);
}

// Respond to INTx interrupts triggered by the device, and return the compute result.
void QemuEduDevice::HandleIrq(async_dispatcher_t* dispatcher, async::IrqBase* irq,
                              zx_status_t status, const zx_packet_interrupt_t* interrupt) {
  irq_.ack();
  if (!pending_callback_.has_value()) {
    FDF_LOG(ERROR, "Received unexpected interrupt!");
    return;
  }
  auto callback = std::move(*pending_callback_);
  pending_callback_ = std::nullopt;
  if (status != ZX_OK) {
    FDF_SLOG(ERROR, "Failed to wait for interrupt", KV("status", zx_status_get_string(status)));
    callback(zx::error(status));
    return;
  }

  // Acknowledge the interrupt with the edu device.
  auto int_status = mmio_->Read32(kInterruptStatusRegisterOffset);
  mmio_->Write32(int_status, kInterruptAcknowledgeRegisterOffset);

  // Deassert the legacy INTx interrupt on the PCI bus.
  auto irq_result = pci_->AckInterrupt();
  if (!irq_result.ok() || irq_result->is_error()) {
    FDF_SLOG(ERROR, "Failed to ack PCI interrupt",
             KV("status", irq_result.ok() ? irq_result->error_value() : irq_result.status()));
    callback(zx::error(ZX_ERR_IO));
    return;
  }

  // Reply with the result.
  uint32_t factorial = mmio_->Read32(kFactorialComputationOffset);
  FDF_SLOG(INFO, "Replying with", KV("factorial", factorial));
  callback(zx::ok(factorial));
}

// Write a challenge value to the liveness check register and return the result.
zx::result<uint32_t> QemuEduDevice::LivenessCheck(uint32_t challenge) {
  // Write the challenge value to the liveness check register.
  mmio_->Write32(challenge, kLivenessCheckOffset);

  // Return the result.
  auto value = mmio_->Read32(kLivenessCheckOffset);
  return zx::ok(value);
}

}  // namespace edu_device

將下列項目新增至驅動程式庫的 Start() 方法，從 MMIO 區域的識別暫存器讀取主要和子版本，並列印至記錄檔：

qemu_edu/drivers/qemu_edu.cc：

// Initialize this driver instance
zx::result<> QemuEduDriver::Start() {
  // ...

  // Map hardware resources from the PCI device
  device_ =
      std::make_shared<edu_device::QemuEduDevice>(dispatcher(), std::move(connect_result.value()));
  auto pci_status = device_->MapInterruptAndMmio();
  if (pci_status.is_error()) {
    return pci_status.take_error();
  }

  // Report the version information from the edu device.
  auto version_reg = device_->IdentificationRegister();
  FDF_SLOG(INFO, "edu device version", KV("major", version_reg.major_version()),
           KV("minor", version_reg.minor_version()));

  return zx::ok();
}

重新啟動模擬器

關閉所有現有的模擬器執行個體：

ffx emu stop --all

啟動新的 Fuchsia 模擬器執行個體，並啟用驅動程式庫架構：

ffx emu start core.x64 --headless

重新載入驅動程式庫

使用 bazel run 指令建構及執行元件目標：

bazel run //fuchsia-codelab/qemu_edu/drivers:pkg.component

bazel run 指令會重建套件並執行 ffx driver register，重新載入驅動程式庫元件。

檢查系統記錄，確認您可以看到更新後的fdf::info() 訊息，其中包含從識別碼暫存器讀取的版本：

ffx log --filter qemu_edu
[driver_manager][driver_manager.cm][I]: [driver_runner.cc:959] Binding fuchsia-pkg://bazel.pkg.component/qemu_edu#meta/qemu_edu.cm to  00_06_0_
[full-drivers:root.sys.platform.pt.PCI0.bus.00_06_0_][qemu-edu,driver][I]: [fuchsia-codelab/qemu_edu/qemu_edu.cc:75] edu device version major=1 minor=0

恭喜！現在，驅動程式可以存取繫結裝置節點提供的 PCI 硬體資源。

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