drm: Check for valid encoder

Cargo.toml

@@ -42,4 +42,4 @@ renderer_glium = ["glium"]
 "wayland-server:0.9.9" = { git = "https://github.com/Drakulix/wayland-rs", branch = "raw_handler_access"}
 "wayland-protocols:0.9.9" = { git = "https://github.com/Drakulix/wayland-rs", branch = "raw_handler_access"}
 "wayland-client:0.9.9" = { git = "https://github.com/Drakulix/wayland-rs", branch = "raw_handler_access"}
-"drm:0.2.1" = { git = "https://github.com/Drakulix/drm-rs", branch = "fix/userdata" }
+"drm:0.2.1" = { git = "https://github.com/Drakulix/drm-rs", branch = "future" }

src/backend/drm/error.rs

@@ -154,6 +154,8 @@ impl error::Error for ModeError {
 pub enum CrtcError {
     /// Selected crtc is already in use by another `DrmBackend`
     AlreadyInUse,
+    /// For the selected crtc no encoder exists that supports all connectors
+    NoSuitableEncoder,
 }
 
 impl fmt::Display for CrtcError {
@@ -170,6 +172,7 @@ impl error::Error for CrtcError {
     fn description(&self) -> &str {
         match self {
             &CrtcError::AlreadyInUse => "Crtc is already in use by another DrmBackend",
+            &CrtcError::NoSuitableEncoder => "Crtc has no supported encoder that can drive all connectors",
         }
     }
 

src/backend/drm/mod.rs

@@ -142,7 +142,7 @@
 
 use backend::graphics::egl::{EGLContext, GlAttributes, PixelFormatRequirements};
 use drm::Device as BasicDevice;
-use drm::control::{connector, crtc, Mode};
+use drm::control::{connector, crtc, encoder, Mode, ResourceInfo};
 use drm::control::Device as ControlDevice;
 
 use gbm::Device as GbmDevice;
@@ -353,6 +353,8 @@ impl<H: DrmHandler + 'static> DrmDevice<H> {
     where
         I: Into<Vec<connector::Handle>>,
     {
+        use std::collections::hash_set::HashSet;
+
         for backend in self.backends.iter() {
             if let Some(backend) = backend.upgrade() {
                 if backend.borrow().is_crtc(crtc) {
@@ -361,6 +363,26 @@ impl<H: DrmHandler + 'static> DrmDevice<H> {
             }
         }
 
+        // check if the given connectors and crtc match
+        let connectors = connectors.into();
+        // get all encoders supported by this device
+        let mut set = self.context.head().head().resource_handles()?.encoders().iter().cloned().collect::<HashSet<encoder::Handle>>();
+        for connector in connectors.iter() {
+            let info = connector::Info::load_from_device(self.context.head().head(), *connector)?;
+            // then check for every connector which encoders it does support
+            let conn_set = info.encoders().iter().cloned().collect::<HashSet<encoder::Handle>>();
+            // and update the list of supported encoders for this combination
+            set = set.intersection(&conn_set).cloned().collect::<HashSet<encoder::Handle>>();
+        }
+
+        // check if there is any encoder left that can be connected to the crtc
+        let encoders: Vec<encoder::Info> = set.iter().map(|handle| encoder::Info::load_from_device(self.context.head().head(), *handle).map_err(DrmError::from)).collect::<Result<Vec<encoder::Info>, DrmError>>()?;
+        if !encoders.iter().any(|enc| enc.supports_crtc(crtc)) {
+            return Err(DrmError::Crtc(CrtcError::NoSuitableEncoder));
+        }
+
+        // configuration is valid, the kernel will figure out the rest
+
         let own_id = self.backends.len();
         let logger = self.logger
             .new(o!("id" => format!("{}", own_id), "crtc" => format!("{:?}", crtc)));