On 05/03/25 - 17:59, Lyude Paul wrote:
This adds some very basic rust bindings for fourcc. We only have a single
format code added for the moment, but this is enough to get a driver
registered.
Signed-off-by: Lyude Paul <ly...@redhat.com>
---
V3:
* Drop FormatList and ModifierList
These aren't actually needed as pointed out by Louis Chauvet
* Add a constant for FORMAT_MOD_INVALID
I realized that we actually need this because the format list isn't
terminated with a 0 like I thought, and we can't pick this up
automatically through bindgen
* Split out the FormatInfo WIP
We'll want this someday, but not yet.
Signed-off-by: Lyude Paul <ly...@redhat.com>
---
rust/kernel/drm/fourcc.rs | 21 +++++++++++++++++++++
rust/kernel/drm/mod.rs | 1 +
2 files changed, 22 insertions(+)
create mode 100644 rust/kernel/drm/fourcc.rs
diff --git a/rust/kernel/drm/fourcc.rs b/rust/kernel/drm/fourcc.rs
new file mode 100644
index 0000000000000..62203478b5955
--- /dev/null
+++ b/rust/kernel/drm/fourcc.rs
@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+
+//! DRM fourcc bindings.
+//!
+//! C header:
[`include/uapi/drm/drm_fourcc.h`](srctree/include/uapi/drm/drm_fourcc.h)
+
+/// Return a fourcc format code.
+const fn fourcc_code(a: u8, b: u8, c: u8, d: u8) -> u32 {
+ (a as u32) | (b as u32) << 8 | (c as u32) << 16 | (d as u32) << 24
+}
+
+// TODO: We manually import this because we don't have a reasonable way of
getting constants from
+// function-like macros in bindgen yet.
+#[allow(dead_code)]
+pub(crate) const FORMAT_MOD_INVALID: u64 = 0xffffffffffffff;
+
+// TODO: We need to automate importing all of these. For the time being, just
add the single one
+// that we need
+
+/// 32 bpp RGB
+pub const XRGB888: u32 = fourcc_code(b'X', b'R', b'2', b'4');
Two questions:
- Can we implement fourcc_code(b"XR24"), so XR24 can be found with grep
without knowing the internals of rust bindings.
- This is maybe "too much abstraction", I don't know what is the
expectation for the kernel, why not creating a FourCC type? This could
avoid confusion with other FourCC code from v4l2? This could also be
complex to automate the generation, so it is maybe a bad idea.
#[repr(transparent)]
struct FourCC(u32);
and then implement From<[u8; 4]> and From<u32>?
Thanks,
Louis Chauvet
diff --git a/rust/kernel/drm/mod.rs b/rust/kernel/drm/mod.rs
index c44760a1332fa..2c12dbd181997 100644
--- a/rust/kernel/drm/mod.rs
+++ b/rust/kernel/drm/mod.rs
@@ -5,5 +5,6 @@
pub mod device;
pub mod drv;
pub mod file;
+pub mod fourcc;
pub mod gem;
pub mod ioctl;
--
2.48.1
--
Louis Chauvet, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
