[udev] Find the primary gpu by iterating drm devices

udev.cpp

@@ -18,7 +18,12 @@ You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *********************************************************************/
 #include "udev.h"
+// Qt
+#include <QByteArray>
+#include <QScopedPointer>
+// system
 #include <libudev.h>
+#include <functional>
 
 namespace KWin
 {
@@ -35,4 +40,145 @@ Udev::~Udev()
     }
 }
 
+class UdevEnumerate
+{
+public:
+    UdevEnumerate(Udev *udev);
+    ~UdevEnumerate();
+
+    enum class Match {
+        SubSystem,
+        SysName
+    };
+    void addMatch(Match match, const char *name);
+    void scan();
+    UdevDevice::Ptr find(std::function<bool(const UdevDevice::Ptr &)> test);
+
+private:
+    Udev *m_udev;
+
+    struct EnumerateDeleter
+    {
+        static inline void cleanup(udev_enumerate *e)
+        {
+            udev_enumerate_unref(e);
+        }
+    };
+    QScopedPointer<udev_enumerate, EnumerateDeleter> m_enumerate;
+};
+
+UdevEnumerate::UdevEnumerate(Udev *udev)
+    : m_udev(udev)
+    , m_enumerate(udev_enumerate_new(*m_udev))
+{
+}
+
+UdevEnumerate::~UdevEnumerate() = default;
+
+void UdevEnumerate::addMatch(UdevEnumerate::Match match, const char *name)
+{
+    if (m_enumerate.isNull()) {
+        return;
+    }
+    switch (match) {
+    case Match::SubSystem:
+        udev_enumerate_add_match_subsystem(m_enumerate.data(), name);
+        break;
+    case Match::SysName:
+        udev_enumerate_add_match_sysname(m_enumerate.data(), name);
+        break;
+    default:
+        Q_UNREACHABLE();
+        break;
+    }
+}
+
+void UdevEnumerate::scan()
+{
+    if (m_enumerate.isNull()) {
+        return;
+    }
+    udev_enumerate_scan_devices(m_enumerate.data());
+}
+
+UdevDevice::Ptr UdevEnumerate::find(std::function<bool(const UdevDevice::Ptr &device)> test)
+{
+    if (m_enumerate.isNull()) {
+        return UdevDevice::Ptr();
+    }
+    udev_list_entry *it = udev_enumerate_get_list_entry(m_enumerate.data());
+    UdevDevice::Ptr firstFound;
+    while (it) {
+        auto current = it;
+        it = udev_list_entry_get_next(it);
+        auto device = m_udev->deviceFromSyspath(udev_list_entry_get_name(current));
+        if (!device) {
+            continue;
+        }
+        if (test(device)) {
+            return std::move(device);
+        }
+        if (!firstFound) {
+            firstFound.swap(device);
+        }
+    }
+    return std::move(firstFound);
+}
+
+UdevDevice::Ptr Udev::primaryGpu()
+{
+    if (!m_udev) {
+        return UdevDevice::Ptr();
+    }
+    UdevEnumerate enumerate(this);
+    enumerate.addMatch(UdevEnumerate::Match::SubSystem, "drm");
+    enumerate.addMatch(UdevEnumerate::Match::SysName, "card[0-9]*");
+    enumerate.scan();
+    return enumerate.find([](const UdevDevice::Ptr &device) {
+        // TODO: check seat
+        auto pci = device->getParentWithSubsystemDevType("pci");
+        if (!pci) {
+            return false;
+        }
+        const char *systAttrValue = udev_device_get_sysattr_value(pci, "boot_vga");
+        if (systAttrValue && qstrcmp(systAttrValue, "1") == 0) {
+            return true;
+        }
+        return false;
+    });
+}
+
+UdevDevice::Ptr Udev::deviceFromSyspath(const char *syspath)
+{
+    return std::move(UdevDevice::Ptr(new UdevDevice(udev_device_new_from_syspath(m_udev, syspath))));
+}
+
+UdevDevice::UdevDevice(udev_device *device)
+    : m_device(device)
+{
+}
+
+UdevDevice::~UdevDevice()
+{
+    if (m_device) {
+        udev_device_unref(m_device);
+    }
+}
+
+udev_device *UdevDevice::getParentWithSubsystemDevType(const char *subsystem, const char *devtype) const
+{
+    if (!m_device) {
+        return nullptr;
+    }
+    return udev_device_get_parent_with_subsystem_devtype(m_device, subsystem, devtype);
+}
+
+const char *UdevDevice::devNode()
+{
+    if (!m_device) {
+        return nullptr;
+    }
+    return udev_device_get_devnode(m_device);
+}
+
 }

udev.h

@@ -19,12 +19,36 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *********************************************************************/
 #ifndef KWIN_UDEV_H
 #define KWIN_UDEV_H
+#include <memory>
 
 struct udev;
+struct udev_device;
 
 namespace KWin
 {
 
+
+class UdevDevice
+{
+public:
+    UdevDevice(udev_device *device);
+    ~UdevDevice();
+
+    udev_device *getParentWithSubsystemDevType(const char *subsystem, const char *devtype = nullptr) const;
+    const char *devNode();
+
+    operator udev_device*() const {
+        return m_device;
+    }
+    operator udev_device*() {
+        return m_device;
+    }
+    typedef std::unique_ptr<UdevDevice> Ptr;
+
+private:
+    udev_device *m_device;
+};
+
 class Udev
 {
 public:
@@ -34,6 +58,8 @@ public:
     bool isValid() const {
         return m_udev != nullptr;
     }
+    UdevDevice::Ptr primaryGpu();
+    UdevDevice::Ptr deviceFromSyspath(const char *syspath);
     operator udev*() const {
         return m_udev;
     }