fallback: support FallbackDevice<GbmDevice, EglStreamDevice> for automatic nvidia support

src/backend/drm/common/fallback.rs

@@ -2,9 +2,20 @@
 //! Types to make fallback device initialization easier
 //!
 
+#[cfg(feature = "backend_drm_egl")]
+use crate::backend::drm::egl::{Arguments as EglDeviceArguments, EglDevice, Error as EglDeviceError};
 #[cfg(all(feature = "backend_drm_atomic", feature = "backend_drm_legacy"))]
 use crate::backend::drm::{atomic::AtomicDrmDevice, legacy::LegacyDrmDevice};
 use crate::backend::drm::{common::Error, Device, DeviceHandler, RawDevice, RawSurface, Surface};
+#[cfg(all(feature = "backend_drm_gbm", feature = "backend_drm_eglstream"))]
+use crate::backend::drm::{
+    eglstream::{EglStreamDevice, Error as EglStreamError},
+    gbm::{Error as GbmError, GbmDevice},
+};
+#[cfg(feature = "backend_drm_egl")]
+use crate::backend::egl::context::{GlAttributes, PixelFormatRequirements};
+#[cfg(feature = "backend_drm_egl")]
+use crate::backend::egl::native::{Backend, NativeDisplay, NativeSurface};
 use crate::backend::egl::Error as EGLError;
 #[cfg(feature = "use_system_lib")]
 use crate::backend::egl::{display::EGLBufferReader, EGLGraphicsBackend};
@@ -36,23 +47,25 @@ pub enum FallbackDevice<D1: Device + 'static, D2: Device + 'static> {
     Fallback(D2),
 }
 
-struct FallbackDeviceHandlerD1<E, C, S1, S2, D1, D2>(
+struct FallbackDeviceHandlerD1<E1, E2, C, S1, S2, D1, D2>(
     Box<dyn DeviceHandler<Device = FallbackDevice<D1, D2>> + 'static>,
 )
 where
-    E: std::error::Error + Send + 'static,
+    E1: std::error::Error + Send + 'static,
+    E2: std::error::Error + Send + 'static,
     C: IntoIterator<Item = connector::Handle> + 'static,
-    S1: Surface<Error = E, Connectors = C> + 'static,
+    S1: Surface<Error = E1, Connectors = C> + 'static,
-    S2: Surface<Error = E, Connectors = C> + 'static,
+    S2: Surface<Error = E2, Connectors = C> + 'static,
     D1: Device<Surface = S1> + 'static,
     D2: Device<Surface = S2> + 'static;
 
-impl<E, C, S1, S2, D1, D2> DeviceHandler for FallbackDeviceHandlerD1<E, C, S1, S2, D1, D2>
+impl<E1, E2, C, S1, S2, D1, D2> DeviceHandler for FallbackDeviceHandlerD1<E1, E2, C, S1, S2, D1, D2>
 where
-    E: std::error::Error + Send + 'static,
+    E1: std::error::Error + Send + 'static,
+    E2: std::error::Error + Send + 'static,
     C: IntoIterator<Item = connector::Handle> + 'static,
-    S1: Surface<Error = E, Connectors = C> + 'static,
+    S1: Surface<Error = E1, Connectors = C> + 'static,
-    S2: Surface<Error = E, Connectors = C> + 'static,
+    S2: Surface<Error = E2, Connectors = C> + 'static,
     D1: Device<Surface = S1> + 'static,
     D2: Device<Surface = S2> + 'static,
 {
@@ -61,28 +74,30 @@ where
     fn vblank(&mut self, crtc: crtc::Handle) {
         self.0.vblank(crtc)
     }
-    fn error(&mut self, error: E) {
+    fn error(&mut self, error: E1) {
-        self.0.error(error);
+        self.0.error(EitherError::Either(error));
     }
 }
 
-struct FallbackDeviceHandlerD2<E, C, S1, S2, D1, D2>(
+struct FallbackDeviceHandlerD2<E1, E2, C, S1, S2, D1, D2>(
     Box<dyn DeviceHandler<Device = FallbackDevice<D1, D2>> + 'static>,
 )
 where
-    E: std::error::Error + Send + 'static,
+    E1: std::error::Error + Send + 'static,
+    E2: std::error::Error + Send + 'static,
     C: IntoIterator<Item = connector::Handle> + 'static,
-    S1: Surface<Error = E, Connectors = C> + 'static,
+    S1: Surface<Error = E1, Connectors = C> + 'static,
-    S2: Surface<Error = E, Connectors = C> + 'static,
+    S2: Surface<Error = E2, Connectors = C> + 'static,
     D1: Device<Surface = S1> + 'static,
     D2: Device<Surface = S2> + 'static;
 
-impl<E, C, S1, S2, D1, D2> DeviceHandler for FallbackDeviceHandlerD2<E, C, S1, S2, D1, D2>
+impl<E1, E2, C, S1, S2, D1, D2> DeviceHandler for FallbackDeviceHandlerD2<E1, E2, C, S1, S2, D1, D2>
 where
-    E: std::error::Error + Send + 'static,
+    E1: std::error::Error + Send + 'static,
+    E2: std::error::Error + Send + 'static,
     C: IntoIterator<Item = connector::Handle> + 'static,
-    S1: Surface<Error = E, Connectors = C> + 'static,
+    S1: Surface<Error = E1, Connectors = C> + 'static,
-    S2: Surface<Error = E, Connectors = C> + 'static,
+    S2: Surface<Error = E2, Connectors = C> + 'static,
     D1: Device<Surface = S1> + 'static,
     D2: Device<Surface = S2> + 'static,
 {
@@ -91,8 +106,8 @@ where
     fn vblank(&mut self, crtc: crtc::Handle) {
         self.0.vblank(crtc)
     }
-    fn error(&mut self, error: E) {
+    fn error(&mut self, error: E2) {
-        self.0.error(error);
+        self.0.error(EitherError::Or(error));
     }
 }
 
@@ -147,9 +162,33 @@ pub enum FallbackSurface<S1: Surface, S2: Surface> {
     Fallback(S2),
 }
 
+/// Enum uniting two kinds of possible errors.
+#[derive(Debug, thiserror::Error)]
+pub enum EitherError<E1: std::error::Error + 'static, E2: std::error::Error + 'static> {
+    /// Either this error
+    #[error("{0}")]
+    Either(#[source] E1),
+    /// Or this error
+    #[error("{0}")]
+    Or(#[source] E2),
+}
+
+impl<E1, E2> Into<SwapBuffersError> for EitherError<E1, E2>
+where
+    E1: std::error::Error + Into<SwapBuffersError> + 'static,
+    E2: std::error::Error + Into<SwapBuffersError> + 'static,
+{
+    fn into(self) -> SwapBuffersError {
+        match self {
+            EitherError::Either(err) => err.into(),
+            EitherError::Or(err) => err.into(),
+        }
+    }
+}
+
 #[cfg(all(feature = "backend_drm_atomic", feature = "backend_drm_legacy"))]
 impl<A: AsRawFd + Clone + 'static> FallbackDevice<AtomicDrmDevice<A>, LegacyDrmDevice<A>> {
-    /// Try to initialize an [`AtomicDrmDevice`](::backend::drm:;atomic::AtomicDrmDevice)
+    /// Try to initialize an [`AtomicDrmDevice`](::backend::drm::atomic::AtomicDrmDevice)
     /// and fall back to a [`LegacyDrmDevice`] if atomic-modesetting is not supported.
     ///
     /// # Arguments
@@ -203,6 +242,146 @@ impl<A: AsRawFd + Clone + 'static> FallbackDevice<AtomicDrmDevice<A>, LegacyDrmD
     }
 }
 
+#[cfg(all(
+    feature = "backend_drm_gbm",
+    feature = "backend_drm_eglstream",
+    feature = "backend_udev"
+))]
+type GbmOrEglStreamError<D> = EitherError<
+    GbmError<<<D as Device>::Surface as Surface>::Error>,
+    EglStreamError<<<D as Device>::Surface as Surface>::Error>,
+>;
+#[cfg(all(
+    feature = "backend_drm_gbm",
+    feature = "backend_drm_eglstream",
+    feature = "backend_udev"
+))]
+impl<D> FallbackDevice<GbmDevice<D>, EglStreamDevice<D>>
+where
+    D: RawDevice + ControlDevice + 'static,
+{
+    /// Try to initialize a [`GbmDevice`](::backend::drm::gbm::GbmDevice)
+    /// or a [`EglStreamDevice`](::backend::drm::eglstream::EglStreamDevice) depending on the used driver.
+    ///
+    /// # Arguments
+    ///
+    /// - `dev` - Open drm device (needs implement [`RawDevice`](::backend::drm::RawDevice))
+    /// - `logger` - Optional [`slog::Logger`] to be used by the resulting device.
+    ///
+    /// # Return
+    ///
+    /// Returns an error, if the choosen device fails to initialize.
+    pub fn new<L>(dev: D, logger: L) -> Result<Self, GbmOrEglStreamError<D>>
+    where
+        L: Into<Option<::slog::Logger>>,
+    {
+        let log = crate::slog_or_stdlog(logger).new(o!("smithay_module" => "backend_drm_fallback"));
+
+        let driver = crate::backend::udev::driver(dev.device_id()).expect("Failed to query device");
+        info!(log, "Drm device driver: {:?}", driver);
+        if driver.as_ref().and_then(|x| x.to_str()) == Some("nvidia") {
+            Ok(FallbackDevice::Fallback(
+                EglStreamDevice::new(dev, log).map_err(EitherError::Or)?,
+            ))
+        } else {
+            Ok(FallbackDevice::Preference(
+                GbmDevice::new(dev, log.clone()).map_err(EitherError::Either)?,
+            ))
+        }
+    }
+}
+
+#[cfg(feature = "backend_drm_egl")]
+type EglUnderlying<D1, D2> = EitherError<
+    EglDeviceError<<<D1 as Device>::Surface as Surface>::Error>,
+    EglDeviceError<<<D2 as Device>::Surface as Surface>::Error>,
+>;
+
+#[cfg(feature = "backend_drm_egl")]
+type FallbackEglDevice<B1, D1, B2, D2> = FallbackDevice<EglDevice<B1, D1>, EglDevice<B2, D2>>;
+
+#[cfg(feature = "backend_drm_egl")]
+impl<D1, D2> FallbackDevice<D1, D2>
+where
+    D1: Device + 'static,
+    <D1 as Device>::Surface: NativeSurface<Error = <<D1 as Device>::Surface as Surface>::Error>,
+    D2: Device + 'static,
+    <D2 as Device>::Surface: NativeSurface<Error = <<D2 as Device>::Surface as Surface>::Error>,
+{
+    /// Try to create a new [`EglDevice`] from a [`FallbackDevice`] containing two compatible device types.
+    ///
+    /// This helper function is necessary as implementing [`NativeDevice`](::backend::egl::native::NativeDevice) for [`FallbackDevice`] is impossible
+    /// as selecting the appropriate [`Backend`](::backend::egl::native::Backend) would be impossible without knowing
+    /// the underlying device type, that was selected by [`FallbackDevice`].
+    ///
+    /// Returns an error if the context creation was not successful.
+    pub fn new_egl<B1, B2, L>(
+        dev: FallbackDevice<D1, D2>,
+        logger: L,
+    ) -> Result<FallbackEglDevice<B1, D1, B2, D2>, EglUnderlying<D1, D2>>
+    where
+        B1: Backend<Surface = <D1 as Device>::Surface, Error = <<D1 as Device>::Surface as Surface>::Error>
+            + 'static,
+        D1: NativeDisplay<B1, Arguments = EglDeviceArguments>,
+        B2: Backend<Surface = <D2 as Device>::Surface, Error = <<D2 as Device>::Surface as Surface>::Error>
+            + 'static,
+        D2: NativeDisplay<B2, Arguments = EglDeviceArguments>,
+        L: Into<Option<::slog::Logger>>,
+    {
+        let log = crate::slog_or_stdlog(logger).new(o!("smithay_module" => "backend_drm_fallback"));
+        match dev {
+            FallbackDevice::Preference(gbm) => match EglDevice::new(gbm, log) {
+                Ok(dev) => Ok(FallbackDevice::Preference(dev)),
+                Err(err) => Err(EglUnderlying::<D1, D2>::Either(err)),
+            },
+            FallbackDevice::Fallback(eglstream) => match EglDevice::new(eglstream, log) {
+                Ok(dev) => Ok(FallbackDevice::Fallback(dev)),
+                Err(err) => Err(EglUnderlying::<D1, D2>::Or(err)),
+            },
+        }
+    }
+
+    /// Try to create a new [`EglDevice`] from a [`FallbackDevice`] containing two compatible device types with
+    /// the given attributes and requirements as defaults for new surfaces.
+    ///
+    /// This helper function is necessary as implementing [`NativeDevice`](::backend::egl::native::NativeDevice) for [`FallbackDevice`] is impossible
+    /// as selecting the appropriate [`Backend`](::backend::egl::native::Backend) would be impossible without knowing
+    /// the underlying device type, that was selected by [`FallbackDevice`].
+    ///
+    /// Returns an error if the context creation was not successful.
+    pub fn new_egl_with_defaults<B1, B2, L>(
+        dev: FallbackDevice<D1, D2>,
+        default_attributes: GlAttributes,
+        default_requirements: PixelFormatRequirements,
+        logger: L,
+    ) -> Result<FallbackEglDevice<B1, D1, B2, D2>, EglUnderlying<D1, D2>>
+    where
+        B1: Backend<Surface = <D1 as Device>::Surface, Error = <<D1 as Device>::Surface as Surface>::Error>
+            + 'static,
+        D1: NativeDisplay<B1, Arguments = EglDeviceArguments>,
+        B2: Backend<Surface = <D2 as Device>::Surface, Error = <<D2 as Device>::Surface as Surface>::Error>
+            + 'static,
+        D2: NativeDisplay<B2, Arguments = EglDeviceArguments>,
+        L: Into<Option<::slog::Logger>>,
+    {
+        let log = crate::slog_or_stdlog(logger).new(o!("smithay_module" => "backend_drm_fallback"));
+        match dev {
+            FallbackDevice::Preference(gbm) => {
+                match EglDevice::new_with_defaults(gbm, default_attributes, default_requirements, log) {
+                    Ok(dev) => Ok(FallbackDevice::Preference(dev)),
+                    Err(err) => Err(EglUnderlying::<D1, D2>::Either(err)),
+                }
+            }
+            FallbackDevice::Fallback(eglstream) => {
+                match EglDevice::new_with_defaults(eglstream, default_attributes, default_requirements, log) {
+                    Ok(dev) => Ok(FallbackDevice::Fallback(dev)),
+                    Err(err) => Err(EglUnderlying::<D1, D2>::Or(err)),
+                }
+            }
+        }
+    }
+}
+
 macro_rules! fallback_device_impl {
     ($func_name:ident, $self:ty, $return:ty, $($arg_name:ident : $arg_ty:ty),*) => {
         fn $func_name(self: $self, $($arg_name : $arg_ty),*) -> $return {
@@ -219,6 +398,19 @@ macro_rules! fallback_device_impl {
         fallback_device_impl!($func_name, $self, ());
     };
 }
+macro_rules! fallback_device_err_impl {
+    ($func_name:ident, $self:ty, $return:ty, $($arg_name:ident : $arg_ty:ty),*) => {
+        fn $func_name(self: $self, $($arg_name : $arg_ty),*) -> $return {
+            match self {
+                FallbackDevice::Preference(dev) => dev.$func_name($($arg_name),*).map_err(EitherError::Either),
+                FallbackDevice::Fallback(dev) => dev.$func_name($($arg_name),*).map_err(EitherError::Or),
+            }
+        }
+    };
+    ($func_name:ident, $self:ty, $return:ty) => {
+        fallback_device_err_impl!($func_name, $self, $return,);
+    };
+}
 
 macro_rules! fallback_surface_impl {
     ($func_name:ident, $self:ty, $return:ty, $($arg_name:ident : $arg_ty:ty),*) => {
@@ -236,6 +428,16 @@ macro_rules! fallback_surface_impl {
         fallback_surface_impl!($func_name, $self, ());
     };
 }
+macro_rules! fallback_surface_err_impl {
+    ($func_name:ident, $self:ty, $return:ty, $($arg_name:ident : $arg_ty:ty),*) => {
+        fn $func_name(self: $self, $($arg_name : $arg_ty),*) -> $return {
+            match self {
+                FallbackSurface::Preference(dev) => dev.$func_name($($arg_name),*).map_err(EitherError::Either),
+                FallbackSurface::Fallback(dev) => dev.$func_name($($arg_name),*).map_err(EitherError::Or),
+            }
+        }
+    };
+}
 
 impl<D1: Device, D2: Device> AsRawFd for FallbackDevice<D1, D2> {
     fallback_device_impl!(as_raw_fd, &Self, RawFd);
@@ -243,13 +445,14 @@ impl<D1: Device, D2: Device> AsRawFd for FallbackDevice<D1, D2> {
 impl<D1: Device + BasicDevice, D2: Device + BasicDevice> BasicDevice for FallbackDevice<D1, D2> {}
 impl<D1: Device + ControlDevice, D2: Device + ControlDevice> ControlDevice for FallbackDevice<D1, D2> {}
 
-impl<E, C, S1, S2, D1, D2> Device for FallbackDevice<D1, D2>
+impl<E1, E2, C, S1, S2, D1, D2> Device for FallbackDevice<D1, D2>
 where
-    // Connectors and Error need to match for both Surfaces
+    // Connectors need to match for both Surfaces
-    E: std::error::Error + Send + 'static,
+    E1: std::error::Error + Send + 'static,
+    E2: std::error::Error + Send + 'static,
     C: IntoIterator<Item = connector::Handle> + 'static,
-    S1: Surface<Error = E, Connectors = C> + 'static,
+    S1: Surface<Error = E1, Connectors = C> + 'static,
-    S2: Surface<Error = E, Connectors = C> + 'static,
+    S2: Surface<Error = E2, Connectors = C> + 'static,
     D1: Device<Surface = S1> + 'static,
     D2: Device<Surface = S2> + 'static,
 {
@@ -268,18 +471,20 @@ where
         crtc: crtc::Handle,
         mode: Mode,
         connectors: &[connector::Handle],
-    ) -> Result<Self::Surface, E> {
+    ) -> Result<Self::Surface, EitherError<E1, E2>> {
         match self {
             FallbackDevice::Preference(dev) => Ok(FallbackSurface::Preference(
-                dev.create_surface(crtc, mode, connectors)?,
+                dev.create_surface(crtc, mode, connectors)
+                    .map_err(EitherError::Either)?,
             )),
             FallbackDevice::Fallback(dev) => Ok(FallbackSurface::Fallback(
-                dev.create_surface(crtc, mode, connectors)?,
+                dev.create_surface(crtc, mode, connectors)
+                    .map_err(EitherError::Or)?,
             )),
         }
     }
     fallback_device_impl!(process_events, &mut Self);
-    fallback_device_impl!(resource_handles, &Self, Result<ResourceHandles, E>);
+    fallback_device_err_impl!(resource_handles, &Self, Result<ResourceHandles, EitherError<E1, E2>>);
     fallback_device_impl!(get_connector_info, &Self, Result<connector::Info, DrmError>, conn: connector::Handle);
     fallback_device_impl!(get_crtc_info, &Self, Result<crtc::Info, DrmError>, crtc: crtc::Handle);
     fallback_device_impl!(get_encoder_info, &Self, Result<encoder::Info, DrmError>, enc: encoder::Handle);
@@ -288,13 +493,14 @@ where
 }
 
 // Impl RawDevice where underlying types implement RawDevice
-impl<E, C, S1, S2, D1, D2> RawDevice for FallbackDevice<D1, D2>
+impl<E1, E2, C, S1, S2, D1, D2> RawDevice for FallbackDevice<D1, D2>
 where
-    // Connectors and Error need to match for both Surfaces
+    // Connectors need to match for both Surfaces
-    E: std::error::Error + Send + 'static,
+    E1: std::error::Error + Send + 'static,
+    E2: std::error::Error + Send + 'static,
     C: IntoIterator<Item = connector::Handle> + 'static,
-    S1: RawSurface + Surface<Error = E, Connectors = C> + 'static,
+    S1: RawSurface + Surface<Error = E1, Connectors = C> + 'static,
-    S2: RawSurface + Surface<Error = E, Connectors = C> + 'static,
+    S2: RawSurface + Surface<Error = E2, Connectors = C> + 'static,
     D1: RawDevice<Surface = S1> + 'static,
     D2: RawDevice<Surface = S2> + 'static,
 {
@@ -308,41 +514,47 @@ impl<D1: Device + EGLGraphicsBackend + 'static, D2: Device + EGLGraphicsBackend
     fallback_device_impl!(bind_wl_display, &Self, Result<EGLBufferReader, EGLError>, display : &Display);
 }
 
-impl<E, C, S1, S2> Surface for FallbackSurface<S1, S2>
+impl<E1, E2, C, S1, S2> Surface for FallbackSurface<S1, S2>
 where
-    // Connectors and Error need to match for both Surfaces
+    // Connectors need to match for both Surfaces
-    E: std::error::Error + Send + 'static,
+    E1: std::error::Error + Send + 'static,
+    E2: std::error::Error + Send + 'static,
     C: IntoIterator<Item = connector::Handle> + 'static,
-    S1: Surface<Error = E, Connectors = C> + 'static,
+    S1: Surface<Error = E1, Connectors = C> + 'static,
-    S2: Surface<Error = E, Connectors = C> + 'static,
+    S2: Surface<Error = E2, Connectors = C> + 'static,
 {
-    type Error = E;
+    type Error = EitherError<E1, E2>;
     type Connectors = C;
 
     fallback_surface_impl!(crtc, &Self, crtc::Handle);
     fallback_surface_impl!(current_connectors, &Self, C);
     fallback_surface_impl!(pending_connectors, &Self, C);
-    fallback_surface_impl!(add_connector, &Self, Result<(), E>, conn: connector::Handle);
+    fallback_surface_err_impl!(add_connector, &Self, Result<(), EitherError<E1, E2>>, conn: connector::Handle);
-    fallback_surface_impl!(remove_connector, &Self, Result<(), E>, conn: connector::Handle);
+    fallback_surface_err_impl!(remove_connector, &Self, Result<(), EitherError<E1, E2>>, conn: connector::Handle);
-    fallback_surface_impl!(set_connectors, &Self, Result<(), E>, conns: &[connector::Handle]);
+    fallback_surface_err_impl!(set_connectors, &Self, Result<(), EitherError<E1, E2>>, conns: &[connector::Handle]);
     fallback_surface_impl!(current_mode, &Self, Mode);
     fallback_surface_impl!(pending_mode, &Self, Mode);
-    fallback_surface_impl!(use_mode, &Self, Result<(), E>, mode: Mode);
+    fallback_surface_err_impl!(use_mode, &Self, Result<(), EitherError<E1, E2>>, mode: Mode);
 }
 
-impl<E, C, S1, S2> RawSurface for FallbackSurface<S1, S2>
+impl<E1, E2, C, S1, S2> RawSurface for FallbackSurface<S1, S2>
 where
-    E: std::error::Error + Send + 'static,
+    E1: std::error::Error + Send + 'static,
+    E2: std::error::Error + Send + 'static,
     C: IntoIterator<Item = connector::Handle> + 'static,
-    S1: RawSurface + Surface<Error = E, Connectors = C> + 'static,
+    S1: RawSurface + Surface<Error = E1, Connectors = C> + 'static,
-    S2: RawSurface + Surface<Error = E, Connectors = C> + 'static,
+    S2: RawSurface + Surface<Error = E2, Connectors = C> + 'static,
 {
     fallback_surface_impl!(commit_pending, &Self, bool);
-    fallback_surface_impl!(commit, &Self, Result<(), E>, fb: framebuffer::Handle);
+    fallback_surface_err_impl!(commit, &Self, Result<(), EitherError<E1, E2>>, fb: framebuffer::Handle);
-    fn page_flip(&self, framebuffer: framebuffer::Handle) -> Result<(), E> {
+    fn page_flip(&self, framebuffer: framebuffer::Handle) -> Result<(), EitherError<E1, E2>> {
         match self {
-            FallbackSurface::Preference(dev) => RawSurface::page_flip(dev, framebuffer),
+            FallbackSurface::Preference(dev) => {
-            FallbackSurface::Fallback(dev) => RawSurface::page_flip(dev, framebuffer),
+                RawSurface::page_flip(dev, framebuffer).map_err(EitherError::Either)
+            }
+            FallbackSurface::Fallback(dev) => {
+                RawSurface::page_flip(dev, framebuffer).map_err(EitherError::Or)
+            }
         }
     }
 }
@@ -353,29 +565,32 @@ impl<S1: Surface + AsRawFd, S2: Surface + AsRawFd> AsRawFd for FallbackSurface<S
 impl<S1: Surface + BasicDevice, S2: Surface + BasicDevice> BasicDevice for FallbackSurface<S1, S2> {}
 impl<S1: Surface + ControlDevice, S2: Surface + ControlDevice> ControlDevice for FallbackSurface<S1, S2> {}
 
-impl<E1, E2, C, CF, S1, S2> CursorBackend for FallbackSurface<S1, S2>
+impl<E1, E2, E3, E4, C, CF, S1, S2> CursorBackend for FallbackSurface<S1, S2>
 where
     E1: std::error::Error + Send + 'static,
-    E2: 'static,
+    E2: std::error::Error + Send + 'static,
+    E3: std::error::Error + 'static,
+    E4: std::error::Error + 'static,
     CF: ?Sized,
     C: IntoIterator<Item = connector::Handle> + 'static,
-    S1: Surface<Error = E1, Connectors = C> + CursorBackend<CursorFormat = CF, Error = E2> + 'static,
+    S1: Surface<Error = E1, Connectors = C> + CursorBackend<CursorFormat = CF, Error = E3> + 'static,
-    S2: Surface<Error = E1, Connectors = C> + CursorBackend<CursorFormat = CF, Error = E2> + 'static,
+    S2: Surface<Error = E2, Connectors = C> + CursorBackend<CursorFormat = CF, Error = E4> + 'static,
 {
     type CursorFormat = CF;
-    type Error = E2;
+    type Error = EitherError<E3, E4>;
 
-    fallback_surface_impl!(set_cursor_position, &Self, Result<(), E2>, x: u32, y: u32);
+    fallback_surface_err_impl!(set_cursor_position, &Self, Result<(), EitherError<E3, E4>>, x: u32, y: u32);
-    fallback_surface_impl!(set_cursor_representation, &Self, Result<(), E2>, buffer: &Self::CursorFormat, hotspot: (u32, u32));
+    fallback_surface_err_impl!(set_cursor_representation, &Self, Result<(), EitherError<E3, E4>>, buffer: &Self::CursorFormat, hotspot: (u32, u32));
 }
 
 #[cfg(feature = "renderer_gl")]
-impl<E, C, S1, S2> GLGraphicsBackend for FallbackSurface<S1, S2>
+impl<E1, E2, C, S1, S2> GLGraphicsBackend for FallbackSurface<S1, S2>
 where
-    E: std::error::Error + Send + 'static,
+    E1: std::error::Error + Send + 'static,
+    E2: std::error::Error + Send + 'static,
     C: IntoIterator<Item = connector::Handle> + 'static,
-    S1: Surface<Error = E, Connectors = C> + GLGraphicsBackend + 'static,
+    S1: Surface<Error = E1, Connectors = C> + GLGraphicsBackend + 'static,
-    S2: Surface<Error = E, Connectors = C> + GLGraphicsBackend + 'static,
+    S2: Surface<Error = E2, Connectors = C> + GLGraphicsBackend + 'static,
 {
     fallback_surface_impl!(swap_buffers, &Self, Result<(), SwapBuffersError>);
     fallback_surface_impl!(get_proc_address, &Self, *const c_void, symbol: &str);

src/backend/drm/egl/mod.rs

@@ -46,7 +46,7 @@ pub enum Error<U: std::error::Error + std::fmt::Debug + std::fmt::Display + 'sta
     Underlying(#[source] U),
 }
 
-type Arguments = (crtc::Handle, Mode, Vec<connector::Handle>);
+pub(crate) type Arguments = (crtc::Handle, Mode, Vec<connector::Handle>);
 type BackendRef<D> = Weak<EglSurfaceInternal<<D as Device>::Surface>>;
 
 /// Representation of an egl device to create egl rendering surfaces