[PATCH 2/5] gpu: nova-core: firmware: add support for common firmware header

[Alexandre Courbot <acourbot@nvidia.com>]

Several firmware files loaded from userspace feature a common header
that describes their payload. Add basic support for it so subsequent
patches can leverage it.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
---
 drivers/gpu/nova-core/firmware.rs | 62 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)

diff --git a/drivers/gpu/nova-core/firmware.rs b/drivers/gpu/nova-core/firmware.rs
index 2931912ddba0ea1fe6d027ccec70b39cdb40344a..ccb4d19f8fa76b0e844252dede5f50b37c590571 100644
--- a/drivers/gpu/nova-core/firmware.rs
+++ b/drivers/gpu/nova-core/firmware.rs
@@ -4,11 +4,13 @@
 //! to be loaded into a given execution unit.
 
 use core::marker::PhantomData;
+use core::mem::size_of;
 
 use kernel::device;
 use kernel::firmware;
 use kernel::prelude::*;
 use kernel::str::CString;
+use kernel::transmute::FromBytes;
 
 use crate::dma::DmaObject;
 use crate::falcon::FalconFirmware;
@@ -150,6 +152,66 @@ fn no_patch_signature(self) -> FirmwareDmaObject<F, Signed> {
     }
 }
 
+/// Header common to most firmware files.
+#[repr(C)]
+#[derive(Debug, Clone)]
+struct BinHdr {
+    /// Magic number, must be `0x10de`.
+    bin_magic: u32,
+    /// Version of the header.
+    bin_ver: u32,
+    /// Size in bytes of the binary (to be ignored).
+    bin_size: u32,
+    /// Offset of the start of the application-specific header.
+    header_offset: u32,
+    /// Offset of the start of the data payload.
+    data_offset: u32,
+    /// Size in bytes of the data payload.
+    data_size: u32,
+}
+
+// SAFETY: all bit patterns are valid for this type, and it doesn't use interior mutability.
+unsafe impl FromBytes for BinHdr {}
+
+// A firmware blob starting with a `BinHdr`.
+struct BinFirmware<'a> {
+    hdr: BinHdr,
+    fw: &'a [u8],
+}
+
+#[expect(dead_code)]
+impl<'a> BinFirmware<'a> {
+    /// Interpret `fw` as a firmware image starting with a [`BinHdr`], and returns the
+    /// corresponding [`BinFirmware`] that can be used to extract its payload.
+    fn new(fw: &'a firmware::Firmware) -> Result<Self> {
+        const BIN_MAGIC: u32 = 0x10de;
+        let fw = fw.data();
+
+        fw.get(0..size_of::<BinHdr>())
+            // Extract header.
+            .and_then(BinHdr::from_bytes_copy)
+            // Validate header.
+            .and_then(|hdr| {
+                if hdr.bin_magic == BIN_MAGIC {
+                    Some(hdr)
+                } else {
+                    None
+                }
+            })
+            .map(|hdr| Self { hdr, fw })
+            .ok_or(EINVAL)
+    }
+
+    /// Returns the data payload of the firmware, or `None` if the data range is out of bounds of
+    /// the firmware image.
+    fn data(&self) -> Option<&[u8]> {
+        let fw_start = self.hdr.data_offset as usize;
+        let fw_size = self.hdr.data_size as usize;
+
+        self.fw.get(fw_start..fw_start + fw_size)
+    }
+}
+
 pub(crate) struct ModInfoBuilder<const N: usize>(firmware::ModInfoBuilder<N>);
 
 impl<const N: usize> ModInfoBuilder<N> {

-- 
2.50.1