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Update OpenBSD support to new drm API introduced in 6.9 #216

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Update OpenBSD support to new drm API introduced in 6.9 #216

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9dc0832
openbsd: Fix OpenBSD /dev/dri/* node name constants
tobhe Mar 3, 2025
8947c81
openbsd: Add dependency for libc 0.2.171
tobhe Mar 3, 2025
3422a4c
openbsd: implement openbsd /dev/dri/* interface
tobhe Jun 15, 2025
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3 changes: 3 additions & 0 deletions Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,9 @@ rustix = { version = "0.38.22", features = ["mm", "fs"] }
[target.'cfg(target_os = "freebsd")'.dependencies]
libc = "0.2"

[target.'cfg(target_os = "openbsd")'.dependencies]
libc = "0.2.171"

[dev-dependencies]
image = { version = "0.24", default-features = false, features = ["png"] }
rustix = { version = "0.38.22", features = ["event", "mm"] }
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15 changes: 0 additions & 15 deletions src/node/constants.rs
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Expand Up @@ -21,25 +21,10 @@ pub const DRM_MAJOR: u32 = 87;
pub const DRM_MAJOR: u32 = 226;

/// Primary DRM node prefix.
#[cfg(not(target_os = "openbsd"))]
pub const PRIMARY_NAME: &str = "card";

/// Primary DRM node prefix.
#[cfg(target_os = "openbsd")]
pub const PRIMARY_NAME: &str = "drm";

/// Control DRM node prefix.
#[cfg(not(target_os = "openbsd"))]
pub const CONTROL_NAME: &str = "controlD";

/// Control DRM node prefix.
#[cfg(target_os = "openbsd")]
pub const CONTROL_NAME: &str = "drmC";

/// Render DRM node prefix.
#[cfg(not(target_os = "openbsd"))]
pub const RENDER_NAME: &str = "renderD";

/// Render DRM node prefix.
#[cfg(target_os = "openbsd")]
pub const RENDER_NAME: &str = "drmR";
42 changes: 38 additions & 4 deletions src/node/mod.rs
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Expand Up @@ -231,6 +231,40 @@ fn devname(dev: dev_t) -> Option<String> {
Some(String::from_utf8(dev_name).expect("Returned device name is not valid utf8"))
}

#[cfg(target_os = "openbsd")]
use std::sync::Mutex;

#[cfg(target_os = "openbsd")]
static DEVNAME_LOCK: Mutex<()> = Mutex::new(());
Comment on lines +234 to +238
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Would it make sense to keep this static locally inside the function for now? And/or do we expect other calls to devname()?

Note that this won't help if user code - through other means - calls libc::devname() without knowing about "your / our" lock 😅

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Would it make sense to keep this static locally inside the function for now? And/or do we expect other calls to devname()?

Sure, I can do that

Note that this won't help if user code - through other means - calls libc::devname() without knowing about "your / our" lock 😅

True, but that's how the underlying API works so not much we can do about it imho.

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While I suggested the lock, I wonder if we should instead mark devname unsafe and all functions using it, while documenting that this is unsound to call from multiple threads on some platforms.


#[cfg(target_os = "openbsd")]
fn devname(dev: dev_t) -> Option<String> {
use std::ffi::CStr;

let _lock = DEVNAME_LOCK.lock().unwrap();
let buf = unsafe {
libc::devname(
dev,
libc::S_IFCHR, // Must be S_IFCHR or S_IFBLK
)
};

if buf.is_null() {
return None;
}

let dev_str =
unsafe { CStr::from_ptr(buf).to_str() }.expect("Returned device name is not valid utf8");
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I think to_str() can be outside of the unsafe block where .expect() already resides.


// If no device matches the specified values, or no information is
// available, a pointer to the string "??" is returned.
if dev_str == "??" {
return None;
}

Some(dev_str.to_owned())
}

/// Returns if the given device by major:minor pair is a DRM device.
#[cfg(target_os = "linux")]
pub fn is_device_drm(dev: dev_t) -> bool {
Expand All @@ -241,7 +275,7 @@ pub fn is_device_drm(dev: dev_t) -> bool {
}

/// Returns if the given device by major:minor pair is a DRM device.
#[cfg(target_os = "freebsd")]
#[cfg(any(target_os = "freebsd", target_os = "openbsd"))]
pub fn is_device_drm(dev: dev_t) -> bool {
devname(dev).map_or(false, |dev_name| {
dev_name.starts_with("drm/")
Expand All @@ -252,7 +286,7 @@ pub fn is_device_drm(dev: dev_t) -> bool {
}

/// Returns if the given device by major:minor pair is a DRM device.
#[cfg(not(any(target_os = "linux", target_os = "freebsd")))]
#[cfg(not(any(target_os = "linux", target_os = "freebsd", target_os = "openbsd")))]
pub fn is_device_drm(dev: dev_t) -> bool {
major(dev) == DRM_MAJOR
}
Expand Down Expand Up @@ -313,7 +347,7 @@ pub fn dev_path(dev: dev_t, ty: NodeType) -> io::Result<PathBuf> {
}

/// Returns the path of a specific type of node from the DRM device described by major and minor device numbers.
#[cfg(target_os = "freebsd")]
#[cfg(any(target_os = "freebsd", target_os = "openbsd"))]
pub fn dev_path(dev: dev_t, ty: NodeType) -> io::Result<PathBuf> {
// Based on libdrm `drmGetMinorNameForFD`. Should be updated if the code
// there is replaced with anything more sensible...
Expand Down Expand Up @@ -351,7 +385,7 @@ pub fn dev_path(dev: dev_t, ty: NodeType) -> io::Result<PathBuf> {
}

/// Returns the path of a specific type of node from the DRM device described by major and minor device numbers.
#[cfg(not(any(target_os = "linux", target_os = "freebsd")))]
#[cfg(not(any(target_os = "linux", target_os = "freebsd", target_os = "openbsd")))]
pub fn dev_path(dev: dev_t, ty: NodeType) -> io::Result<PathBuf> {
use std::io::ErrorKind;

Expand Down