From 5a6dfdc9de9e1d93f44cd0b18093adc84c1dbee0 Mon Sep 17 00:00:00 2001
From: Lyude Paul <lyude@redhat.com>
Date: Mon, 4 Mar 2024 19:01:10 -0500
Subject: [PATCH] WIP: rust/drm: Add fourcc bindings
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.
TODO:
* Write up something to automatically generate constants from the fourcc
headers
Signed-off-by: Lyude Paul <lyude@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
---
rust/kernel/drm/fourcc.rs | 62 +++++++++++++++++++++++++++++++++++++++
rust/kernel/drm/mod.rs | 1 +
2 files changed, 63 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..14111abbc236b
--- /dev/null
+++ b/rust/kernel/drm/fourcc.rs
@@ -0,0 +1,62 @@
+use bindings;
+
+/// 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.
+pub(crate) const FORMAT_MOD_INVALID: u64 = 0xffffffffffffff;
+
+// TODO: Figure out a more automated way of importing this
+pub const XRGB888: u32 = fourcc_code(b'X', b'R', b'2', b'4');
+
+#[repr(transparent)]
+#[derive(Copy, Clone)]
+pub struct FormatInfo {
+ inner: bindings::drm_format_info,
+}
+
+impl FormatInfo {
+ // SAFETY: `ptr` must point to a valid instance of a `bindings::drm_format_info`
+ pub(super) unsafe fn from_raw<'a>(ptr: *const bindings::drm_format_info) -> &'a Self {
+ // SAFETY: Our data layout is identical
+ unsafe { &*ptr.cast() }
+ }
+
+ /// The number of color planes (1 to 3)
+ pub const fn num_planes(&self) -> u8 {
+ self.inner.num_planes
+ }
+
+ /// Does the format embed an alpha component?
+ pub const fn has_alpha(&self) -> bool {
+ self.inner.has_alpha
+ }
+
+ /// The total number of components (color planes + alpha channel, if there is one)
+ pub const fn num_components(&self) -> u8 {
+ self.num_planes() + self.has_alpha() as u8
+ }
+
+ /// Number of bytes per block (per plane), where blocks are defined as a rectangle of pixels
+ /// which are stored next to each other in a byte aligned memory region.
+ pub fn char_per_block(&self) -> &[u8] {
+ // SAFETY: The union we access here is just for descriptive purposes on the C side, both
+ // members are identical in data layout
+ unsafe { &self.inner.__bindgen_anon_1.char_per_block[..self.num_components() as _] }
+ }
+}
+
+impl AsRef<bindings::drm_format_info> for FormatInfo {
+ fn as_ref(&self) -> &bindings::drm_format_info {
+ &self.inner
+ }
+}
+
+impl From<bindings::drm_format_info> for FormatInfo {
+ fn from(value: bindings::drm_format_info) -> Self {
+ Self { inner: value }
+ }
+}
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;
--
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