gKeyMapper/daemon/g910_device.cpp

// gKeyMapper daemon - raw HID access to the keyboard's vendor interface.
//
// Uses the kernel's hidraw interface instead of libusb.  hidraw provides
// non-exclusive access: the kernel driver (usbhid) stays attached, and other
// tools (OpenRGB, etc.) can open the same device at the same time.  This
// avoids the exclusive claim that blocked OpenRGB from detecting the keyboard.

#include "g910_device.h"

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cerrno>
#include <fcntl.h>
#include <unistd.h>
#include <poll.h>
#include <sys/ioctl.h>
#include <linux/hidraw.h>

namespace gkeymapper::daemon {

GKeyDevice::~GKeyDevice() {
    close();
}

// Scan /sys/class/hidraw for a node whose HID_ID matches vendor:product and
// whose sysfs path points at interface 1 (the vendor-specific one).  Returns
// the minor number (>= 0) or -1.
int GKeyDevice::find_hidraw_node(uint16_t vendor, uint16_t product) {
    char id_str[64];
    std::snprintf(id_str, sizeof(id_str), "0003:%08X:%08X", (unsigned)vendor, (unsigned)product);

    for (int i = 0; i < 64; ++i) {
        char path[512];
        std::snprintf(path, sizeof(path), "/sys/class/hidraw/hidraw%d/device/uevent", i);
        FILE* f = std::fopen(path, "r");
        if (!f) {
            continue;
        }
        char buf[2048];
        size_t n = std::fread(buf, 1, sizeof(buf) - 1, f);
        std::fclose(f);
        buf[n] = '\0';

        // Check HID_ID matches our vendor:product.
        if (std::strstr(buf, id_str) == nullptr) {
            continue;
        }

        // Check the sysfs path contains ":1." (interface 1, the vendor one).
        // The readlink gives us the full device path.
        char linkpath[512];
        std::snprintf(linkpath, sizeof(linkpath), "/sys/class/hidraw/hidraw%d", i);
        char resolved[1024];
        ssize_t rlen = readlink(linkpath, resolved, sizeof(resolved) - 1);
        if (rlen < 0) {
            continue;
        }
        resolved[rlen] = '\0';

        // The resolved path contains the interface number in the form
        // <device>:<config>.<interface>.  Interface 1 (vendor-specific) has
        // config 1, so the path contains ":1.1" (altsetting 1) or ":1.0".
        // We check the uevent's HID_PHYS instead, which contains "input1"
        // for interface 1 and "input0" for interface 0.
        if (std::strstr(buf, "input1") == nullptr) {
            continue;
        }

        return i;
    }
    return -1;
}

bool GKeyDevice::open(bool quiet) {
    if (fd_ >= 0) {
        return true;
    }

    // Find a supported profile first (by vendor/product).
    // We iterate all profiles and try to find a matching hidraw node.
    const auto& profs = profiles();
    const DeviceProfile* matched = nullptr;
    int node = -1;

    for (const DeviceProfile& p : profs) {
        node = find_hidraw_node(p.vendor, p.product);
        if (node >= 0) {
            matched = &p;
            break;
        }
    }

    if (!matched || node < 0) {
        if (!quiet) {
            std::fprintf(stderr, "gkeymapper-daemon: no supported keyboard found\n");
        }
        return false;
    }
    profile_ = matched;

    char devpath[64];
    std::snprintf(devpath, sizeof(devpath), "/dev/hidraw%d", node);

    fd_ = ::open(devpath, O_RDWR | O_NONBLOCK);
    if (fd_ < 0) {
        if (!quiet) {
            std::fprintf(stderr, "gkeymapper-daemon: could not open %s (%s)\n",
                         devpath, std::strerror(errno));
        }
        profile_ = nullptr;
        return false;
    }

    // Disable the default G-key binding (G-keys mapped to F-keys) if needed.
    // Done after open so disable_binding() can use the fd.
    // (disable_binding is called separately by main.cpp)

    std::fprintf(stderr, "gkeymapper-daemon: %s found (hidraw%d)\n",
                 profile_->name, node);
    return true;
}

bool GKeyDevice::disable_binding() {
    if (fd_ < 0 || !profile_) {
        return false;
    }
    if (!profile_->disableBinding) {
        return true;
    }

    for (const Report& command : profile_->disableCommands) {
        // HID SET_REPORT (feature report).  The first byte of the command
        // is the report ID.
        int len = static_cast<int>(command.size());
        // HIDIOCSFEATURE takes a buffer where byte 0 is the report ID.
        std::vector<uint8_t> buf(command.begin(), command.end());
        int rc = ioctl(fd_, HIDIOCSFEATURE(len), buf.data());
        if (rc < 0) {
            std::fprintf(stderr, "gkeymapper-daemon: disable-binding ioctl failed (%s)\n",
                         std::strerror(errno));
            return false;
        }
    }

    // Drain confirmation reports.
    uint8_t scratch[64];
    for (int i = 0; i < 6; ++i) {
        if (read_report(scratch, sizeof(scratch), 200) <= 0) {
            break;
        }
    }
    return true;
}

int GKeyDevice::read_report(uint8_t* buffer, int length, int timeoutMs) {
    if (fd_ < 0) {
        return -1;
    }

    struct pollfd pfd;
    pfd.fd = fd_;
    pfd.events = POLLIN;
    pfd.revents = 0;

    int rc = poll(&pfd, 1, timeoutMs);
    if (rc < 0) {
        if (errno == EINTR) {
            return 0;
        }
        return -1;
    }
    if (rc == 0) {
        return 0; // timeout
    }
    if (!(pfd.revents & POLLIN)) {
        return 0;
    }

    ssize_t n = ::read(fd_, buffer, length);
    if (n < 0) {
        if (errno == EAGAIN || errno == EWOULDBLOCK) {
            return 0;
        }
        return -1;
    }
    return static_cast<int>(n);
}

void GKeyDevice::close() {
    if (fd_ >= 0) {
        ::close(fd_);
    }
    fd_ = -1;
    profile_ = nullptr;
}

} // namespace gkeymapper::daemon