message_usb.cpp

// Copyright 2024 Google LLC
//
// 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 "message_usb.hpp"

#include "usb_util.hpp"

#include <algorithm>
#include <chrono>
#include <cstdint>
#include <format>
#include <stdexcept>
#include <thread>
#include <utility>
#include <vector>

using namespace std::chrono_literals;

namespace google
{
namespace hoth
{

MessageUSB::MessageUSB(std::string_view usb_id, LibusbIntf* libusb,
                       bool unit_test) :
    ctx(libusb),
    dev(find_dev(ctx, usb_id)),
    interface(
        find_intf(dev, kMailboxClass, kMailboxSubClasses, kMailboxProtocol)),
    in(find_ep(interface, LIBUSB_ENDPOINT_IN)),
    out(find_ep(interface, LIBUSB_ENDPOINT_OUT)),
    maxInSize(std::min(in.wMaxPacketSize, kMaxBulkTransferSize)),
    maxOutSize(std::min(out.wMaxPacketSize, kMaxBulkTransferSize)),
    handle(dev.open()),
    claim(handle.claim_interface(interface.bInterfaceNumber))
{
    if (maxOutSize < sizeof(ReqHeader) + 1)
    {
        throw std::invalid_argument("Output packet size too small");
    }
    if (maxInSize < sizeof(RspHeader) + 1)
    {
        throw std::invalid_argument("Input packet size too small");
    }
    // Workaround for hoth producing bad responses if transfers
    // start too quickly after initialization.
    if (!unit_test)
    {
        using namespace std::literals::chrono_literals;
        std::this_thread::sleep_for(1s);
    }
}

void MessageUSB::send(const uint8_t* buf, size_t size, size_t seek)
{
    std::array<uint8_t, kMaxBulkTransferSize> data;
    ReqHeader req;
    req.type = ReqHeader::kWrite;
    req.offset = seek;
    while (size > 0)
    {
        req.length = std::min(size, maxOutSize - sizeof(ReqHeader));
        memcpy(data.data(), &req, sizeof(req));
        memcpy(data.data() + sizeof(req), buf, req.length);
        size_t sent = req.length + sizeof(req);
        if (handle.bulk_transfer(out, data.data(), sent, 0ms) != sent)
        {
            throw std::runtime_error("Failed to submit entire write request");
        }

        RspHeader rsp;
        size_t recvd = handle.bulk_transfer(in, data.data(), data.size(), 0ms);
        if (recvd < sizeof(rsp))
        {
            throw std::runtime_error("Failed to receive write status");
        }
        memcpy(&rsp, data.data(), sizeof(rsp));
        if (rsp.status != 0)
        {
            throw std::runtime_error(
                std::format("Mailbox returned an error on write {:02x}",
                            static_cast<uint8_t>(rsp.status)));
        }

        buf += req.length;
        size -= req.length;
        req.offset += req.length;
    }
}

void MessageUSB::recv(uint8_t* buf, size_t size, size_t seek)
{
    std::array<uint8_t, kMaxBulkTransferSize> data;
    ReqHeader req;
    req.type = ReqHeader::kRead;
    req.offset = seek;
    while (size > 0)
    {
        req.length = std::min(size, maxInSize - sizeof(RspHeader));
        memcpy(data.data(), &req, sizeof(req));
        if (handle.bulk_transfer(out, data.data(), sizeof(req), 0ms) !=
            sizeof(req))
        {
            throw std::runtime_error("Failed to send entire read request");
        }

        size_t recvd = handle.bulk_transfer(in, data.data(), data.size(), 0ms);
        if (recvd < sizeof(RspHeader))
        {
            throw std::runtime_error("Failed to receive header");
        }
        RspHeader rsp;
        memcpy(&rsp, data.data(), sizeof(rsp));
        if (rsp.status != 0)
        {
            throw std::runtime_error(
                std::format("Mailbox returned an error on read {:02x}",
                            static_cast<uint8_t>(rsp.status)));
        }

        recvd = std::min(size, recvd - sizeof(rsp));
        memcpy(buf, data.data() + sizeof(rsp), recvd);
        buf += recvd;
        size -= recvd;
        req.offset += recvd;
    }
}

} // namespace hoth
} // namespace google