外设组件互连 (PCI) 设备使用各种接口向系统公开资源，包括中断、内存映射 I/O (MMIO) 寄存器和直接内存访问 (DMA) 缓冲区。Fuchsia 驱动程序通过父设备节点的功能访问这些资源。对于 PCI 设备，父级会提供 fuchsia.hardware.pci/Device FIDL 协议的实例，使驱动程序能够配置设备。
在本部分中，您将添加相关功能，以在 edu 设备上访问以下 MMIO 寄存器：
| 地址偏移量 | 注册 | R/W | 说明 |
|---|---|---|---|
| 0x00 | 身份识别 | RO | 主要 / 次要版本标识符 |
| 0x04 | 卡片活跃性检查 | RW | 验证操作 |
| 0x08 | 阶乘计算 | RW | 计算存储值的阶乘 |
| 0x20 | 状态 | RW | 用于表明操作已完成的位字段 |
完成本部分后，项目应具有以下目录结构：
//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
连接到家长设备
如需从父设备节点访问 fuchsia.hardware.pci/Device 接口，请将 fuchsia.hardware.pci.Service 功能添加到驱动程序的组件清单中：
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' },
],
}
这样，驱动程序就可以打开与父设备的连接，并访问其提供的硬件专用协议。
更新驱动程序的 Start() 方法，以访问驱动程序初始化期间父设备提供的 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_SLOG(INFO, "edu driver loaded successfully");
return zx::ok();
}
} // namespace qemu_edu
设置中断和 MMIO
连接到 fuchsia.hardware.pci/Device 后，您可以开始将必要的设备资源映射到驱动程序。
在项目目录中创建新的 qemu_edu/drivers/edu_device.h 文件，其中包含以下内容：
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/mmio/mmio.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_
创建新的 qemu_edu/drivers/edu_device.cc 文件，并添加以下代码以实现 MapInterruptAndMmio() 方法。此方法会执行以下任务：
- 访问相应 PCI 区域的基址寄存器 (BAR)。
- 针对该区域提取 Fuchsia 的 VMO（虚拟内存对象）。
- 在该区域周围创建 MMIO 缓冲区，以访问各个寄存器。
- 配置映射到设备中断的中断请求 (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
将新的设备资源添加到驱动程序类中：
qemu_edu/drivers/qemu_edu.h:
#include <lib/driver/component/cpp/driver_base.h>
#include <lib/driver/devfs/cpp/connector.h>
#include <fidl/examples.qemuedu/cpp/wire.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)),
devfs_connector_(fit::bind_member<&QemuEduDriver::Serve>(this)) {}
virtual ~QemuEduDriver() = default;
// Start hook called by the driver factory.
zx::result<> Start() override;
private:
zx::result<> ExportToDevfs();
void Serve(fidl::ServerEnd<examples_qemuedu::Device> request);
fidl::WireSyncClient<fuchsia_driver_framework::Node> node_;
fidl::WireSyncClient<fuchsia_driver_framework::NodeController> controller_;
driver_devfs::Connector<examples_qemuedu::Device> devfs_connector_;
std::shared_ptr<edu_device::QemuEduDevice> device_;
};
} // namespace qemu_edu
更新驱动程序的 Run() 方法，以在驱动程序初始化期间调用新方法：
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_SLOG(INFO, "edu driver loaded successfully");
return zx::ok();
}
更新驱动程序 build 配置以添加新的源文件并依赖于 fuchsia.hardware.pci 的 FIDL 绑定库：
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_llcpp_cc",
"@fuchsia_sdk//pkg/driver_component_cpp",
"@fuchsia_sdk//pkg/driver_devfs_cpp",
"@fuchsia_sdk//pkg/hwreg",
"@fuchsia_sdk//pkg/mmio",
],
)
读取设备寄存器
将基础资源映射到驱动程序中后，您可以访问各个寄存器。将以下寄存器定义添加到项目的 qemu_edu/drivers/edu_device.h 文件中：
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/mmio/mmio.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
这会将设备规范中提供的寄存器偏移量声明为常量。Fuchsia 的 hwreg 库封装了表示位字段的寄存器，使它们更易于访问，而无需执行单独的按位操作。
在 qemu_edu/drivers/edu_device.cc 中实现以下其他方法以与 MMIO 区域交互，以读取和写入数据到相应的 edu 设备寄存器：
ComputeFactorial()：将输入值写入阶乘计算寄存器，并等待设备使用中断异步发出信号，已完成。HandleIrq()：从阶乘寄存器中读取计算结果，并将其报告给待处理回调。LivenessCheck()：向活跃性检查寄存器写入质询值，并确认预期结果。
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
将以下代码添加到驱动程序的 Start() 方法中，以便从标识寄存器从 MMIO 区域读取主要版本和次要版本，并将其输出到日志：
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();
}
重启模拟器
关停所有现有的模拟器实例：
ffx emu stop --all
启动启用了驱动程序框架的 Fuchsia 模拟器的新实例：
ffx emu start core.x64 --headless
重新加载驱动程序
使用 bazel run 命令构建并执行组件目标：
bazel run //fuchsia-codelab/qemu_edu/drivers:pkg.component
bazel run 命令会重新构建软件包并运行 ffx driver register 以重新加载驱动程序组件。
检查系统日志，验证是否可以看到更新后的 FDF_SLOG() 消息，其中包含从标识寄存器读取的版本：
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-pkg-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！您的驱动程序现在可以访问绑定设备节点提供的 PCI 硬件资源。