c - TI 游戏 handle 示例项目中的这个中断禁用/启用对有什么作用吗？

Question

此代码来自 TI 的 ek-tm4c123gxl usb-dev-gamepad CCS 示例，将 volatile 枚举分配给 g_iGamepadState 包装在中断禁用/启用对中。对我来说，它看起来像一个错误；它应该包装发送报告函数 USBDHIDGamepadSendReport() 以防止发送中途中断。我认为这可以防止单个存储指令的中断，这是多余的。

下面是引用枚举的所有代码...

volatile enum {
    eStateNotConfigured,            // Not yet configured.
    eStateIdle,                     // Connected, not waiting on data to be sent
    eStateSuspend,                  // Suspended
    eStateSending                   // Connected, waiting on data to be sent out
} g_iGamepadState;

...

//*****************************************************************************
//
// Handles asynchronous events from the HID gamepad driver.
//
// \param pvCBData is the event callback pointer provided during
// USBDHIDGamepadInit().  This is a pointer to our gamepad device structure
// (&g_sGamepadDevice).
// \param ui32Event identifies the event we are being called back for.
// \param ui32MsgData is an event-specific value.
// \param pvMsgData is an event-specific pointer.
//
// This function is called by the HID gamepad driver to inform the application
// of particular asynchronous events related to operation of the gamepad HID
// device.
//
// \return Returns 0 in all cases.
//
//*****************************************************************************
uint32_t GamepadHandler(void *pvCBData, uint32_t ui32Event,
        uint32_t ui32MsgData, void *pvMsgData) {
    switch (ui32Event) {
    case USB_EVENT_CONNECTED: {
        g_iGamepadState = eStateIdle;
        break;
    }
    case USB_EVENT_DISCONNECTED: {
        g_iGamepadState = eStateNotConfigured;
        break;
    }
    case USB_EVENT_TX_COMPLETE: {
        g_iGamepadState = eStateIdle;
        break;
    }
    case USB_EVENT_SUSPEND: {
        g_iGamepadState = eStateSuspend;
        break;
    }
    case USB_EVENT_RESUME: {
        g_iGamepadState = eStateIdle;
        break;
    }

    ...

    default: {
        break;
    }
    }

    return (0);
}

...

int main(void) {

    ...

    // Not configured initially.
    g_iGamepadState = eStateNotConfigured;

    ...


    while (1) {
        //
        // Wait here until USB device is connected to a host.
        //
        if (g_GamepadState == eStateIdle) {

            ...

            USBDHIDGamepadSendReport(&g_sGamepadDevice, &sReport,
                    sizeof(sReport));

            //
            // Now sending data but protect this from an interrupt since
            // it can change in interrupt context as well.
            //
            IntMasterDisable();
            g_iGamepadState = eStateSending;
            IntMasterEnable();
        }
    }
}

Answer 1

来自 TI 的 E2E forum ...

I think you are correct. This may be a bug.

空闲 TX 事件有可能在发送报告和更改为发送状态枚举之间返回，这样就永远不会离开发送状态。对于为什么禁用/启用中断对首先存在的原因，这个解释似乎最有意义。