smithay/src/backend/allocator/gbm.rs

//! Module for Buffers created using [libgbm](gbm).
//! 
//! The re-exported [`GbmDevice`](gbm::Device) implements the [`Allocator`](super::Allocator) trait
//! and [`GbmBuffer`](gbm::BufferObject) satisfies the [`Buffer`](super::Buffer) trait while also allowing
//! conversions to and from [dmabufs](super::dmabuf).

use super::{
    dmabuf::{AsDmabuf, Dmabuf},
    Allocator, Buffer, Format, Fourcc, Modifier,
};
pub use gbm::{BufferObject as GbmBuffer, BufferObjectFlags as GbmBufferFlags, Device as GbmDevice};
use std::os::unix::io::AsRawFd;

impl<A: AsRawFd + 'static, T> Allocator<GbmBuffer<T>> for GbmDevice<A> {
    type Error = std::io::Error;

    fn create_buffer(&mut self, width: u32, height: u32, format: Format) -> std::io::Result<GbmBuffer<T>> {
        if format.modifier == Modifier::Invalid || format.modifier == Modifier::Linear {
            let mut usage = GbmBufferFlags::SCANOUT | GbmBufferFlags::RENDERING;
            if format.modifier == Modifier::Linear {
                usage |= GbmBufferFlags::LINEAR;
            }
            self.create_buffer_object(width, height, format.code, usage)
        } else {
            self.create_buffer_object_with_modifiers(
                width,
                height,
                format.code,
                Some(format.modifier).into_iter(),
            )
        }
    }
}

impl<T> Buffer for GbmBuffer<T> {
    fn width(&self) -> u32 {
        self.width().unwrap_or(0)
    }

    fn height(&self) -> u32 {
        self.height().unwrap_or(0)
    }

    fn format(&self) -> Format {
        Format {
            code: self.format().unwrap_or(Fourcc::Argb8888), // we got to return something, but this should never happen anyway
            modifier: self.modifier().unwrap_or(Modifier::Invalid),
        }
    }
}

/// Errors during conversion to a dmabuf handle from a gbm buffer object
#[derive(thiserror::Error, Debug)]
pub enum GbmConvertError {
    /// The gbm device was destroyed
    #[error("The gbm device was destroyed")]
    DeviceDestroyed(#[from] gbm::DeviceDestroyedError),
    /// The buffer consists out of multiple file descriptions, which is currently unsupported
    #[error("Buffer consists out of multiple file descriptors, which is currently unsupported")]
    UnsupportedBuffer,
    /// The conversion returned an invalid file descriptor
    #[error("Buffer returned invalid file descriptor")]
    InvalidFD,
}

impl<T> AsDmabuf for GbmBuffer<T> {
    type Error = GbmConvertError;

    fn export(&self) -> Result<Dmabuf, GbmConvertError> {
        let planes = self.plane_count()? as i32;

        //TODO switch to gbm_bo_get_plane_fd when it lands
        let mut iter = (0i32..planes).map(|i| self.handle_for_plane(i));
        let first = iter.next().expect("Encountered a buffer with zero planes");
        // check that all handles are the same
        let handle = iter.try_fold(first, |first, next| {
            if let (Ok(next), Ok(first)) = (next, first) {
                if unsafe { next.u64_ == first.u64_ } {
                    return Some(Ok(first));
                }
            }
            None
        });
        if handle.is_none() {
            // GBM is lacking a function to get a FD for a given plane. Instead,
            // check all planes have the same handle. We can't use
            // drmPrimeHandleToFD because that messes up handle ref'counting in
            // the user-space driver.
            return Err(GbmConvertError::UnsupportedBuffer); //TODO
        }

        let fds = [self.fd()?, 0, 0, 0];
        //if fds.iter().any(|fd| fd == 0) {
        if fds[0] < 0 {
            return Err(GbmConvertError::InvalidFD);
        }

        let offsets = (0i32..planes)
            .map(|i| self.offset(i))
            .collect::<Result<Vec<u32>, gbm::DeviceDestroyedError>>()?;
        let strides = (0i32..planes)
            .map(|i| self.stride_for_plane(i))
            .collect::<Result<Vec<u32>, gbm::DeviceDestroyedError>>()?;

        Ok(Dmabuf::new(self, planes as usize, &offsets, &strides, &fds).unwrap())
    }
}

impl Dmabuf {
    /// Import a Dmabuf using libgbm, creating a gbm Buffer Object to the same underlying data.
    pub fn import_to<A: AsRawFd + 'static, T>(
        &self,
        gbm: &GbmDevice<A>,
        usage: GbmBufferFlags,
    ) -> std::io::Result<GbmBuffer<T>> {
        let buf = &*self.0;
        if self.has_modifier() || buf.num_planes > 1 || buf.offsets[0] != 0 {
            gbm.import_buffer_object_from_dma_buf_with_modifiers(
                buf.num_planes as u32,
                buf.fds,
                buf.width,
                buf.height,
                buf.format.code,
                usage,
                unsafe { std::mem::transmute::<[u32; 4], [i32; 4]>(buf.strides) },
                unsafe { std::mem::transmute::<[u32; 4], [i32; 4]>(buf.offsets) },
                buf.format.modifier,
            )
        } else {
            gbm.import_buffer_object_from_dma_buf(
                buf.fds[0],
                buf.width,
                buf.height,
                buf.strides[0],
                buf.format.code,
                if buf.format.modifier == Modifier::Linear {
                    usage | GbmBufferFlags::LINEAR
                } else {
                    usage
                },
            )
        }
    }
}