gpu: nova-core: firmware: add ucode descriptor used by FWSEC-FRTS

FWSEC-FRTS is the first firmware we need to run on the GSP falcon in
order to initiate the GSP boot process. Introduce the structure that
describes it.

Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Link: https://lore.kernel.org/r/20250619-nova-frts-v6-16-ecf41ef99252@nvidia.com
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

Author: Gnurou

drivers/gpu/nova-core/firmware.rs

@@ -41,6 +41,51 @@ impl Firmware {
     }
 }
 
+/// Structure used to describe some firmwares, notably FWSEC-FRTS.
+#[repr(C)]
+#[derive(Debug, Clone)]
+pub(crate) struct FalconUCodeDescV3 {
+    /// Header defined by `NV_BIT_FALCON_UCODE_DESC_HEADER_VDESC*` in OpenRM.
+    hdr: u32,
+    /// Stored size of the ucode after the header.
+    stored_size: u32,
+    /// Offset in `DMEM` at which the signature is expected to be found.
+    pub(crate) pkc_data_offset: u32,
+    /// Offset after the code segment at which the app headers are located.
+    pub(crate) interface_offset: u32,
+    /// Base address at which to load the code segment into `IMEM`.
+    pub(crate) imem_phys_base: u32,
+    /// Size in bytes of the code to copy into `IMEM`.
+    pub(crate) imem_load_size: u32,
+    /// Virtual `IMEM` address (i.e. `tag`) at which the code should start.
+    pub(crate) imem_virt_base: u32,
+    /// Base address at which to load the data segment into `DMEM`.
+    pub(crate) dmem_phys_base: u32,
+    /// Size in bytes of the data to copy into `DMEM`.
+    pub(crate) dmem_load_size: u32,
+    /// Mask of the falcon engines on which this firmware can run.
+    pub(crate) engine_id_mask: u16,
+    /// ID of the ucode used to infer a fuse register to validate the signature.
+    pub(crate) ucode_id: u8,
+    /// Number of signatures in this firmware.
+    pub(crate) signature_count: u8,
+    /// Versions of the signatures, used to infer a valid signature to use.
+    pub(crate) signature_versions: u16,
+    _reserved: u16,
+}
+
+// To be removed once that code is used.
+#[expect(dead_code)]
+impl FalconUCodeDescV3 {
+    /// Returns the size in bytes of the header.
+    pub(crate) fn size(&self) -> usize {
+        const HDR_SIZE_SHIFT: u32 = 16;
+        const HDR_SIZE_MASK: u32 = 0xffff0000;
+
+        ((self.hdr & HDR_SIZE_MASK) >> HDR_SIZE_SHIFT) as usize
+    }
+}
+
 pub(crate) struct ModInfoBuilder<const N: usize>(firmware::ModInfoBuilder<N>);
 
 impl<const N: usize> ModInfoBuilder<N> {