ids1024/drm-rs

A low-level abstraction of the Direct Rendering Manager API

drm-rs

A safe interface to the Direct Rendering Manager.

Direct Rendering Manager

The Direct Rendering Manager is a subsystem found on multiple Unix-based operating systems that provides a userspace API to graphics hardware. See the Wikipedia article for more details.

Usage

Basic

The DRM is accessed using ioctls on a file representing a graphics card. These can normally be found in /dev/dri, but can also be opened in other ways (ex. udev).

This crate does not provide a method of opening these files. Instead, the user program must provide a way to access the file descriptor representing the device through the AsRawFd trait. Here is a basic example using File as a backend:

/// A simple wrapper for a device node.
pub struct Card(std::fs::File);

/// Implementing `AsRawFd` is a prerequisite to implementing the traits found
/// in this crate. Here, we are just calling `as_raw_fd()` on the inner File.
impl std::os::unix::io::AsRawFd for Card {
    fn as_raw_fd(&self) -> std::os::unix::io::RawFd {
        self.0.as_raw_fd()
    }
}

/// Simple helper methods for opening a `Card`.
impl Card {
    pub fn open(path: &str) -> Self {
        let mut options = std::fs::OpenOptions::new();
        options.read(true);
        options.write(true);
        Card(options.open(path).unwrap())
    }
}

Finally, you can implement drm::Device to gain access to the basic DRM functionality:

impl drm::Device for Card {}

fn main() {
    let gpu = Card::open("/dev/dri/card0");
    println!("{:#?}", gpu.get_driver().unwrap());
}

Control (modesetting)

See drm::control::Device as well as our mode-setting examples: atomic_modeset and legacy_modeset

Rendering

Rendering is done by creating and attaching framebuffers to crtcs.

A framebuffer is created from anything implementing Buffer like the always available, but very limited, DumbBuffer.

For faster hardware-backed buffers, checkout gbm.rs.