src/posix/platform/hdlc_interface.hpp

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/**
 * @file
 *   This file includes definitions for the HDLC interface to radio (RCP).
 */

#ifndef POSIX_APP_HDLC_INTERFACE_HPP_
#define POSIX_APP_HDLC_INTERFACE_HPP_

#include "openthread-posix-config.h"
#include "platform-posix.h"
#include "lib/hdlc/hdlc.hpp"
#include "lib/spinel/multi_frame_buffer.hpp"
#include "lib/spinel/openthread-spinel-config.h"
#include "lib/spinel/spinel_interface.hpp"

namespace ot {
namespace Posix {

/**
 * Defines an HDLC interface to the Radio Co-processor (RCP)
 *
 */
class HdlcInterface : public ot::Spinel::SpinelInterface
{
public:
    /**
     * Initializes the object.
     *
     * @param[in] aCallback         Callback on frame received
     * @param[in] aCallbackContext  Callback context
     * @param[in] aFrameBuffer      A reference to a `RxFrameBuffer` object.
     *
     */
    HdlcInterface(ReceiveFrameCallback aCallback, void *aCallbackContext, RxFrameBuffer &aFrameBuffer);

    /**
     * This destructor deinitializes the object.
     *
     */
    ~HdlcInterface(void);

    /**
     * Initializes the interface to the Radio Co-processor (RCP)
     *
     * @note This method should be called before reading and sending spinel frames to the interface.
     *
     * @param[in]  aRadioUrl          RadioUrl parsed from radio url.
     *
     * @retval OT_ERROR_NONE          The interface is initialized successfully
     * @retval OT_ERROR_ALREADY       The interface is already initialized.
     * @retval OT_ERROR_INVALID_ARGS  The UART device or executable cannot be found or failed to open/run.
     *
     */
    otError Init(const Url::Url &aRadioUrl);

    /**
     * Deinitializes the interface to the RCP.
     *
     */
    void Deinit(void);

    /**
     * Encodes and sends a spinel frame to Radio Co-processor (RCP) over the socket.
     *
     * This is blocking call, i.e., if the socket is not writable, this method waits for it to become writable for
     * up to `kMaxWaitTime` interval.
     *
     * @param[in] aFrame     A pointer to buffer containing the spinel frame to send.
     * @param[in] aLength    The length (number of bytes) in the frame.
     *
     * @retval OT_ERROR_NONE     Successfully encoded and sent the spinel frame.
     * @retval OT_ERROR_NO_BUFS  Insufficient buffer space available to encode the frame.
     * @retval OT_ERROR_FAILED   Failed to send due to socket not becoming writable within `kMaxWaitTime`.
     *
     */
    otError SendFrame(const uint8_t *aFrame, uint16_t aLength);

    /**
     * Waits for receiving part or all of spinel frame within specified interval.
     *
     * @param[in]  aTimeout  The timeout value in microseconds.
     *
     * @retval OT_ERROR_NONE             Part or all of spinel frame is received.
     * @retval OT_ERROR_RESPONSE_TIMEOUT No spinel frame is received within @p aTimeout.
     *
     */
    otError WaitForFrame(uint64_t aTimeoutUs);

    /**
     * Updates the file descriptor sets with file descriptors used by the radio driver.
     *
     * @param[in,out]   aMainloopContext  A pointer to the mainloop context containing fd_sets.
     *
     */
    void UpdateFdSet(void *aMainloopContext);

    /**
     * Performs radio driver processing.
     *
     * @param[in]   aMainloopContext  A pointer to the mainloop context containing fd_sets.
     *
     */
    void Process(const void *aMainloopContext);

    /**
     * Returns the bus speed between the host and the radio.
     *
     * @returns   Bus speed in bits/second.
     *
     */
    uint32_t GetBusSpeed(void) const { return mBaudRate; }

    /**
     * Hardware resets the RCP.
     *
     * @retval OT_ERROR_NONE            Successfully reset the RCP.
     * @retval OT_ERROR_NOT_IMPLEMENT   The hardware reset is not implemented.
     *
     */
    otError HardwareReset(void) { return OT_ERROR_NOT_IMPLEMENTED; }

    /**
     * Returns the RCP interface metrics.
     *
     * @returns The RCP interface metrics.
     *
     */
    const otRcpInterfaceMetrics *GetRcpInterfaceMetrics(void) const { return &mInterfaceMetrics; }

private:
    /**
     * Is called when RCP is reset to recreate the connection with it.
     *
     */
    otError ResetConnection(void);

    /**
     * Instructs `HdlcInterface` to read and decode data from radio over the socket.
     *
     * If a full HDLC frame is decoded while reading data, this method invokes the `HandleReceivedFrame()` (on the
     * `aCallback` object from constructor) to pass the received frame to be processed.
     *
     */
    void Read(void);

    /**
     * Waits for the socket file descriptor associated with the HDLC interface to become writable within
     * `kMaxWaitTime` interval.
     *
     * @retval OT_ERROR_NONE   Socket is writable.
     * @retval OT_ERROR_FAILED Socket did not become writable within `kMaxWaitTime`.
     *
     */
    otError WaitForWritable(void);

    /**
     * Writes a given frame to the socket.
     *
     * This is blocking call, i.e., if the socket is not writable, this method waits for it to become writable for
     * up to `kMaxWaitTime` interval.
     *
     * @param[in] aFrame  A pointer to buffer containing the frame to write.
     * @param[in] aLength The length (number of bytes) in the frame.
     *
     * @retval OT_ERROR_NONE    Frame was written successfully.
     * @retval OT_ERROR_FAILED  Failed to write due to socket not becoming writable within `kMaxWaitTime`.
     *
     */
    otError Write(const uint8_t *aFrame, uint16_t aLength);

    /**
     * Performs HDLC decoding on received data.
     *
     * If a full HDLC frame is decoded while reading data, this method invokes the `HandleReceivedFrame()` (on the
     * `aCallback` object from constructor) to pass the received frame to be processed.
     *
     * @param[in] aBuffer  A pointer to buffer containing data.
     * @param[in] aLength  The length (number of bytes) in the buffer.
     *
     */
    void Decode(const uint8_t *aBuffer, uint16_t aLength);

    static void HandleHdlcFrame(void *aContext, otError aError);
    void        HandleHdlcFrame(otError aError);

    /**
     * Opens file specified by aRadioUrl.
     *
     * @param[in] aRadioUrl  A reference to object containing path to file and data for configuring
     *                       the connection with tty type file.
     *
     * @retval The file descriptor of newly opened file.
     */
    int OpenFile(const Url::Url &aRadioUrl);

    /**
     * Closes file associated with the file descriptor.
     *
     */
    void CloseFile(void);

#if OPENTHREAD_POSIX_CONFIG_RCP_PTY_ENABLE
    static int ForkPty(const Url::Url &aRadioUrl);
#endif

    enum
    {
        kMaxWaitTime   = 2000, ///< Maximum wait time in Milliseconds for socket to become writable (see `SendFrame`).
        kResetTimeout  = 5000, ///< Maximum wait time in Milliseconds for file to become ready (see `ResetConnection`).
        kOpenFileDelay = 50,   ///< Delay between open file calls, in Milliseconds (see `ResetConnection`).
        kRemoveRcpDelay =
            2000, ///< Delay for removing RCP device from host OS after hard reset (see `ResetConnection`).
    };

    ReceiveFrameCallback mReceiveFrameCallback;
    void                *mReceiveFrameContext;
    RxFrameBuffer       &mReceiveFrameBuffer;

    int             mSockFd;
    uint32_t        mBaudRate;
    Hdlc::Decoder   mHdlcDecoder;
    const Url::Url *mRadioUrl;

    otRcpInterfaceMetrics mInterfaceMetrics;

    // Non-copyable, intentionally not implemented.
    HdlcInterface(const HdlcInterface &);
    HdlcInterface &operator=(const HdlcInterface &);
};

} // namespace Posix
} // namespace ot
#endif // POSIX_APP_HDLC_INTERFACE_HPP_