1  /// Check the `util` module to see how the `Card` structure is implemented.
2  pub mod utils;
3  
4  use crate::utils::*;
5  use rustix::event::PollFlags;
6  use std::{
7      io,
8      os::unix::io::{AsFd, OwnedFd},
9  };
10  
11  impl Card {
simulate_command_submission(&self) -> io::Result<OwnedFd>12      fn simulate_command_submission(&self) -> io::Result<OwnedFd> {
13          // Create a temporary syncobj to receive the command fence.
14          let syncobj = self.create_syncobj(false)?;
15  
16          let sync_file = {
17              // Fake a command submission by signalling the syncobj immediately. The kernel
18              // attaches a null fence object which is always signalled. Other than this, there
19              // isn't a good way to create and signal a fence object from user-mode, so an actual
20              // device is required to test this properly.
21              //
22              // For a real device, the syncobj handle should be passed to a command submission
23              // which is expected to set a fence to be signalled upon completion.
24              self.syncobj_signal(&[syncobj])?;
25  
26              // Export fence set by previous ioctl to file descriptor.
27              self.syncobj_to_fd(syncobj, true)
28          };
29  
30          // The sync file descriptor constitutes ownership of the fence, so the syncobj can be
31          // safely destroyed.
32          self.destroy_syncobj(syncobj)?;
33  
34          sync_file
35      }
36  }
37  
main()38  fn main() {
39      let card = Card::open_global();
40      let sync_file = card.simulate_command_submission().unwrap();
41      let fd = sync_file.as_fd();
42  
43      // Poll for readability. The DRM fence object will directly wake the thread when signalled.
44      //
45      // Alternatively, Tokio's AsyncFd may be used like so:
46      //
47      // use tokio::io::{Interest, unix::AsyncFd};
48      // let afd = AsyncFd::with_interest(sync_file, Interest::READABLE).unwrap();
49      // let future = async move { afd.readable().await.unwrap().retain_ready() };
50      // future.await;
51      let mut poll_fds = [rustix::event::PollFd::new(&fd, PollFlags::IN)];
52      rustix::event::poll(&mut poll_fds, -1).unwrap();
53  }
54