wayland: implement zwp_linux_dmabuf v4

src/drm_feedback.rs

@@ -0,0 +1,58 @@
+use {
+    crate::{gfx_api::GfxContext, utils::oserror::OsError},
+    byteorder::{NativeEndian, WriteBytesExt},
+    std::{io::Write, rc::Rc},
+    thiserror::Error,
+    uapi::{c, OwnedFd},
+};
+
+pub struct DrmFeedback {
+    pub fd: Rc<OwnedFd>,
+    pub size: usize,
+    pub indices: Vec<u16>,
+    pub main_device: c::dev_t,
+}
+
+impl DrmFeedback {
+    pub fn new(ctx: &dyn GfxContext) -> Result<Self, DrmFeedbackError> {
+        let dev_t = uapi::fstat(ctx.gbm().drm.raw())
+            .map_err(OsError::from)?
+            .st_rdev;
+        let data = create_fd_data(ctx);
+        let mut memfd =
+            uapi::memfd_create("drm_feedback", c::MFD_CLOEXEC | c::MFD_ALLOW_SEALING).unwrap();
+        memfd.write_all(&data).unwrap();
+        uapi::lseek(memfd.raw(), 0, c::SEEK_SET).unwrap();
+        uapi::fcntl_add_seals(
+            memfd.raw(),
+            c::F_SEAL_SEAL | c::F_SEAL_GROW | c::F_SEAL_SHRINK | c::F_SEAL_WRITE,
+        )
+        .unwrap();
+        let num_indices = data.len() / 16;
+        let indices = (0..num_indices).map(|v| v as u16).collect();
+        Ok(Self {
+            fd: Rc::new(memfd),
+            size: data.len(),
+            indices,
+            main_device: dev_t,
+        })
+    }
+}
+
+fn create_fd_data(ctx: &dyn GfxContext) -> Vec<u8> {
+    let mut vec = vec![];
+    for (format, info) in &*ctx.formats() {
+        for modifier in info.modifiers.keys() {
+            vec.write_u32::<NativeEndian>(*format).unwrap();
+            vec.write_u32::<NativeEndian>(0).unwrap();
+            vec.write_u64::<NativeEndian>(*modifier).unwrap();
+        }
+    }
+    vec
+}
+
+#[derive(Debug, Error)]
+pub enum DrmFeedbackError {
+    #[error("Could not stat drm device")]
+    Stat(#[from] OsError),
+}